Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners

Federal RegisterMay 18, 2006

Ask Donna

What actually matters in this document.

Text

DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Part 57

RIN 1219-AB29

Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners

AGENCY:

Mine Safety and Health Administration (MSHA), Labor.

ACTION:

Final rule.

SUMMARY:

This final rule revises the May 20, 2006 effective date of the diesel particulate matter (DPM) final concentration limit of 160 micrograms of total carbon (TC) per cubic meter of air (160

μg/m

) promulgated in the 2001 final rule “Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners,” and published in the

Federal Register

on January 19, 2001 (66 FR 5706) and amended on September 19, 2005 (70 FR 55019).

This final rule increases flexibility of compliance for mine operators by allowing staggered effective dates for implementation of the final DPM limit, phased-in over a two-year period, primarily based on feasibility issues which have surfaced since promulgation of the 2001 final rule.

Furthermore this final rule establishes requirements for medical evaluation of miners required to wear respiratory protection and transfer of miners who are medically unable to wear a respirator; deletes the existing provision that restricts newer mines from applying for an extension of time in which to meet the final concentration limit; addresses technological and economic feasibility issues, and the costs and benefits of this rule.

EFFECTIVE DATE:

This final rule is effective on May 18, 2006 except for amendments to § 57.5060(d), which is effective August 16, 2006.

FOR FURTHER INFORMATION CONTACT:

Patricia W. Silvey, Acting Director, Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson Blvd., Room 2350, Arlington, Virginia 22209-3939; 202-693-9440 (telephone); or 202-693-9441 (facsimile).

You may obtain copies of this final rule and the Regulatory Economic Analysis (REA) in alternative formats by calling 202-693-9440. The alternative formats are either a large print version of these documents or electronic files that can be sent to you either on a computer disk or as an attachment to an e-mail. The documents also are available on the Internet at

http://www.msha.gov/REGSINFO.HTM

SUPPLEMENTARY INFORMATION:

Outline of Preamble

This outline will assist the mining community in finding information in this preamble.

I. List of Common Terms

II. Background

A. First Partial Settlement Agreement

B. Second Partial Settlement Agreement

III. Rulemaking History

A. Advance Notice of Proposed Rulemaking (ANPRM) on the Interim and Final Concentration Limits

B. Notice of Proposed Rulemaking (NPRM) on the Interim Limit

C. Final Rule Revising the Interim Concentration Limit

D. September 2005 Notice of Proposed Rulemaking

IV. Risk Assessment

V. Feasibility

A. Technological Feasibility

B. Economic Feasibility

VI. Summary of Benefits

VII. Section 101(a)(9) of the Mine Act

VIII. Section-by-Section Analysis

A. PEL § 57.5060(b)

B. Special Extensions § 57.5060(c)(3)(i)

C. Medical Evaluation and Transfer § 57.5060(d)

D. Diesel Particulate Records § 57.5075(a)

IX. Regulatory Costs

A. Costs of Medical Evaluation and Transfer

B. Costs of Implementing the 160

μg/m

Limit

X. Regulatory Flexibility Act Certification (RFA) and Small Business Regulatory Enforcement Fairness Act (SBREFA)

A. Definition of a Small Mine

B. Factual Basis for Certification

XI. Paperwork Reduction Act

XII. Other Regulatory Considerations

A. The Unfunded Mandates Reform Act of 1995

B. National Environmental Policy Act

C. The Treasury and General Government Appropriations Act of 1999: Assessment of Federal Regulations and Policies on Families

D. Executive Order 12630: Government Actions and Interference With Constitutionally Protected Property Rights

E. Executive Order 12988: Civil Justice Reform

F. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks

G. Executive Order 13132: Federalism

H. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use

J. Executive Order 13272: Proper Consideration of Small Entities in Agency Rulemaking

XIII. Information Quality

XIV. References Cited

XV. Regulatory Text

I. List of Common Terms

Listed below are the common terms used in the preamble.

31 Mine Study

Joint MSHA/Industry Study: Determinations of DPM levels in Underground Metal and Nonmetal Mines.

Commission

Federal Mine Safety and Health Review Commission.

Coefficient of Variation.

DPF

diesel particulate filter.

DPM

diesel particulate matter.

elemental carbon.

ETS

environmental tobacco smoke.

Filter Selection Guide

Diesel Particulate Filter Selection Guide for Diesel-powered Equipment in Metal and Nonmetal Mines.

First Partial Settlement Agreement

66 FR 35518 (2001) & 66 FR 35521 (2001): basis for July 5, 2001 NPRM.

MARG

Methane Awareness Resource Group.

M/NM

metal/non-metal.

MSHA

Mine Safety and Health Administration.

NIOSH

National Institute for Occupational Safety and Health.

NTP

National Toxicology Program.

organic carbon.

PAPR

powered air-purifying respirator.

PEL

permissible exposure limit.

PPM

parts per million.

QRA

quantitative risk assessment.

REA

Regulatory Economic Analysis.

Second Partial Settlement Agreement

67 FR 47296 (2002): basis for August 14, 2003 NPRM.

standard deviation.

SKC

SKC, Inc.

total carbon (the sum of elemental and organic carbon).

USWA

United Steelworkers of America.

USW

United Steelworkers.

μg/cm

micrograms per square centimeter.

μg/m

micrograms per cubic meter.

2001 final rule

January 19, 2001 DPM final rule.

Amended 2001 final rule

2001 final rule amended on February 27, 2002.

2002 final rule

February 27, 2002 final rule.

2002 ANPRM

Advance Notice of Proposed Rulemaking published on September 25, 2002.

2003 NPRM

Notice of Proposed Rulemaking published on August 14, 2003.

2005 final rule

June 6, 2005 final rule.

2005 proposed rule

Notice of Proposed Rulemaking published on September 7, 2005.

II. Background

On January 19, 2001, MSHA published a final rule addressing the health hazards to underground metal and nonmetal miners from exposure to diesel particulate matter (DPM) (66 FR 5706). The rule established new health standards for these miners by requiring, among other things, mine operators to use engineering and work practice controls to reduce DPM to prescribed limits. It set an interim and final DPM concentration limit in the underground metal and nonmetal mining environment with staggered effective dates for implementation of the concentration limits. The interim concentration limit of 400

μg/m

was to become effective on July 20, 2002. The final concentration limit of 160

μg/m

was scheduled to become effective January 20, 2006. In the 2001 final rule, MSHA projected that the mining industry would meet the final concentration limit in their mines through the use of diesel particulate filtration devices, ventilation changes, and the turnover of equipment and engines to less polluting models (66 FR 5713, 5888).

Several mining trade associations and individual mine operators challenged the final rule and the United Steelworkers of America (USWA) intervened in the case, which is now pending in the United States Court of Appeals for the District of Columbia Circuit. The parties agreed to resolve their differences through settlement negotiations with MSHA and we delayed the effective date of certain provisions of the standard.

A. First Partial Settlement Agreement

On July 5, 2001, as a result of an agreement reached in settlement negotiations, MSHA published two notices in the

Federal Register

. One notice (66 FR 35518) delayed the effective date of § 57.5066(b) related to tagging requirements in the maintenance standard. The second notice (66 FR 35521) proposed a rule to make limited revisions to § 57.5066(b) and added a new paragraph to § 57.5067(b) “Engines” regarding the definition of the term “introduced.” MSHA published the final rule on February 27, 2002 (67 FR 9180).

B. Second Partial Settlement Agreement

Settlement negotiations continued on the remaining unresolved issues in the litigation, and on July 15, 2002, the parties finalized a written agreement (67 FR 47296, 47297). Under the agreement, the interim concentration limit of 400

μg/m

became effective on July 20, 2002, without further legal challenge. MSHA afforded mine operators one year to develop and implement good-faith compliance strategies to meet the interim concentration limit, and MSHA agreed to provide compliance assistance during this one-year period. MSHA also agreed to propose rulemaking on several other disputed provisions of the 2001 final rule. The legal challenge to the rule was stayed pending completion of the additional rulemakings.

On July 20, 2003, MSHA began full enforcement of the interim concentration limit of 400

μg/m

. MSHA's enforcement policy was also based on the terms of the second partial settlement agreement and includes the use of elemental carbon (EC) as an analyte to ensure that a citation based on the 400 TC concentration limit is valid and not the result of interferences (67 FR 47298). The policy was discussed with the DPM litigants and stakeholders on July 17, 2003.

III. Rulemaking History

A. Advance Notice of Proposed Rulemaking (ANPRM) on the Interim and Final Concentration Limits

On September 25, 2002, MSHA published an Advance Notice of Proposed Rulemaking (ANPRM) (67 FR 60199). MSHA noted in the ANPRM that the scope of the rulemaking was limited to the terms of the Second Partial Settlement Agreement and posed a series of questions to the mining community related to the 2001 final rule. MSHA also stated its intent to propose a rule to revise the surrogate for the interim and final concentration limits and to propose a DPM control scheme similar to that included in our longstanding hierarchy of controls scheme used in MSHA's air quality standards (30 CFR 56.5001 through 56.5005 and 57.5001 through 57.5005) for M/NM mines. In addition, MSHA stated that it would consider technological and economic feasibility for the underground M/NM mining industry to comply with revised interim and final DPM limits. MSHA determined at that time that some mine operators had begun to implement control technology on their underground diesel-powered equipment. Therefore, MSHA requested relevant information on current experiences with availability of control technology, installation of control technology, effectiveness of control technology to reduce DPM levels, and cost implications of compliance with the 2001 final rule.

B. Notice of Proposed Rulemaking (NPRM) on the Interim Limit

In response to our publication of the ANPRM, some commenters recommended that MSHA propose separate rulemakings for revising the interim and final concentration limits to give MSHA an opportunity to gather further information to establish a final DPM limit, particularly regarding feasibility. In the subsequent notice of proposed rulemaking (NPRM) published on August 14, 2003 (68 FR 48668), MSHA concurred with these commenters and notified the public in the NPRM that we would propose a separate rulemaking to amend the existing final concentration limit of 160

μg/m

. MSHA also requested comments on an appropriate final DPM limit and solicited additional information on feasibility. The proposed rule also addressed the interim concentration limit by proposing a

comparable PEL of 308 μg/m

based on the EC surrogate and included a number of other provisions.

C. Final Rule Revising the Interim Concentration Limit

MSHA published the final rule revising the interim concentration limit on June 6, 2005 (70 FR 32868). This rule changed the interim concentration limit of 400 μg/m

measured by TC to a comparable PEL of 308 μg/m

measured by EC. The rule requires MSHA's longstanding hierarchy of controls that is used for other MSHA exposure-based health standards at M/NM mines, but retains the prohibition on rotation of miners for compliance. Furthermore, the rule, among other things, requires MSHA to consider economic as well as technological feasibility in determining if operators qualify for an extension of time in which to meet the final DPM limit, and deletes the requirement for a control plan.

Currently, the following provisions of the DPM standard are effective: § 57.5060(a), establishing the interim PEL of 308 micrograms of EC per cubic meter of air which is comparable in effect to 400 micrograms of TC per cubic meter of air; § 57.5060(d), Addressing control requirements; § 57.5060(e), Prohibiting rotation of miners for compliance with the DPM standard; § 57.5061, Compliance determinations; § 57.5065, Fueling practices; § 57.5066, Maintenance standards; § 57.5067, Engines; § 57.5070, Miner training; § 57.5071, Exposure monitoring; and, § 57.5075, Diesel particulate records.

D. September 2005 Notice of Proposed Rulemaking

On September 7, 2005, (70 FR 53280) MSHA proposed a rule to phase in the final DPM limit because MSHA was concerned that there may be feasibility issues for some mines to meet that limit by January 20, 2006.

Accordingly, the proposed rule considered staggering the effective date for implementation of the final DPM limit, phased in over a five-year period, primarily based on feasibility issues which had surfaced since promulgation of the 2001 final rule. MSHA also proposed to delete existing § 57.5060(c)(3)(i) that restricts new mines from applying for an extension of time for meeting the final concentration limit. MSHA sought comment and data on an appropriate conversion factor for the final DPM limit, technological implementation issues, and the costs and benefits of the final rule. In addition, MSHA requested comments on the appropriateness of including in a final rule a provision for medical evaluation of miners required to wear respiratory protection and transfer of miners who have been determined by a medical professional to be unable to wear a respirator.

MSHA set hearing dates and a deadline for receiving comments on the September 7, 2005 proposed rule with the expectation that MSHA would complete the rulemaking to phase in the final DPM limit before January 20, 2006.

After publication of the September 7, 2005 proposed rule, MSHA received a request from the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union (USW) for more time to comment on the proposed rule. The USW explained that Hurricane Katrina had placed demands on their resources that would prevent them from participating effectively in the rulemaking under the current schedule for hearings and comments. MSHA recognized the USW's need to devote resources to respond to the aftermath of Hurricane Katrina and the impact that would have on their participation under the current timetable. MSHA also received a request from the National Stone, Sand and Gravel Association (NSSGA) for additional time to comment on the proposed rule and for an additional public hearing in Arlington, Virginia.

Accordingly, due to requests from the USW and NSSGA, MSHA published a notice on September 19, 2005 (70 FR 55018) that changed the public hearing dates from September 2005 to January 2006. MSHA also extended the public comment period from October 14, 2005 to January 27, 2006. Also on September 19, 2005, MSHA issued a second notice delaying the applicability of the final concentration limit of 160TC μg/m

until May 20, 2006.

Public hearings were held on the proposed rule in Arlington, Virginia on January 5, 2006; Salt Lake City, Utah on January 9, 2006; Kansas City, Missouri on January 11, 2006; and Louisville, Kentucky on January 13, 2006. The comment period was scheduled to close on January 27, 2006. However, the National Mining Association and the Methane Awareness Resource Group (MARG) Diesel Coalition requested that the comment period be extended an additional 30 days beyond January 27, 2006 to allow for more time to prepare their comments. Additionally, the Agency received a request from the National Institute for Occupational Safety and Health (NIOSH) for a three week extension. On January 26, 2006, MSHA determined that a three week extension of the comment period was sufficient to allow additional public comment on the proposed rule and extended the comment period until February 17, 2006.

What follows is a discussion of the specific revisions to the 2001 DPM standard. The final rule addresses:

• Section 57.5060(b) addressing the final dpm concentration limit;

• Section 57.5060(c)(3)(i) addressing special extensions;

• Section 57.5060(d)addressing medical evaluation and transfer; and

• Section 57.5075 addressing recordkeeping requirements.

IV. Risk Assessment

A. Introduction

We rely on our comprehensive January 2001 risk assessment published at 66 FR 5752-5855 (as corrected at 66 FR 35518-35520) to support this final rule. This risk assessment was updated in the 2005 final rule (70 FR 32868) establishing the 308EC μg/m

interim permissible exposure limit (PEL). In the following discussion, we will refer to the risk assessment published in the 2001 final rule as the “2001 risk assessment” and the updates published in the 2005 final rule as the “updated 2001 risk assessment.”

The discussion of the 2001 risk assessment in our 2005 final rule presented our evaluation of health risks associated with DPM exposure levels encountered in the mining industry and is based on a review of the scientific literature available through March 31, 2000, along with consideration of all material submitted during the public comment periods for the 2001 and 2005 rulemakings.

The 2001 risk assessment was divided into three main sections. Section 1 (66 FR 5753-5764) contained a discussion of U.S. miner exposures based on field data collected through mid-1998. Section 2 of the 2001 risk assessment (66 FR 5764-5822) reviewed the extensive scientific literature on health effects associated with exposures to DPM. In section 3 of the 2001 risk assessment (66 FR 5822-5855), we evaluated the best available evidence to ascertain whether exposure levels currently existing in mines warranted regulatory action pursuant to the Mine Act. After careful consideration of all the submitted public comments, the 2001 risk assessment established three main conclusions:

1. Exposure to DPM can materially impair miner health or functional capacity. These material impairments include acute sensory irritations and respiratory symptoms (including allergenic responses); premature death from cardiovascular, cardiopulmonary, or respiratory causes; and lung cancer.

2. At DPM levels currently observed in underground mines, many miners are presently at significant risk of incurring these material impairments due to their occupational exposures to DPM over a working lifetime.

3. By reducing DPM concentrations in underground mines, the rule will substantially reduce the risks of material impairment faced by underground miners exposed to DPM at current levels (66 FR 5854-5855).

Exposure to DPM can materially impair miner health or functional capacity. These material impairments include acute sensory irritations and respiratory symptoms (including allergenic responses); premature death from cardiovascular, cardiopulmonary, or respiratory causes; and lung cancer. Scientific evidence gathered after the peer-review of the 2001 risk assessment generally supports our conclusions, and nothing in our reviews suggests that they should be altered.

Some commenters presented critiques challenging the 2001 risk assessment and disputing scientific support for any DPM exposure limit, especially by means of an EC surrogate. Other commenters endorsed the risk assessment and stated that recent scientific publications support our conclusions.

Some commenters continue to question the scientific basis for linking DPM exposures with an increased risk of adverse health effects. Many of these comments are the same as those addressed in the 2005 final rule. We refer the reader to section VI, DPM Exposures and Risk Assessment, in the 2005 final rule (70 FR at 32888) for discussions addressing earlier commenters' positions on the underlying basis of the risk assessment.

After considering the additional peer-reviewed scientific literature submitted in response to the proposed rule, and all of the comments, we did not identify any reason to reduce our concern with regard to adverse health risks associated with DPM exposure as identified in the 2001 risk assessment.

Section IV.B, summarizes the DPM exposure data that became available after publication of the 2001 final rule. Section IV.C, Health Effects, summarizes additional scientific literature pertaining to adverse health effects of DPM and fine particulates submitted to the record since our 2005 final rule. The reader is encouraged to refer to the 2001 quantitative risk assessment (66 FR 5752-5855) that reviewed the health effects associated with exposure to DPM. This discussion evaluates the extent to which literature added to the record changes the conclusions of the 2001 risk assessment. Section IV.D, Significance of Risk, supplements Section 2 of the 2001 risk assessment (66 FR 5764-5822) by addressing comments related to the risk assessment.

We reviewed comments on the potential health effects of substituting EC for TC as a surrogate measure of DPM. We believe that the issue of an appropriate surrogate for a measure of DPM is separate from the issue of determining whether adverse health effects are caused by whole DPM or a specific component of DPM. The 2001 risk assessment is definitive in explaining relevant adverse health effects caused by exposure to DPM. The risk assessment accurately portrays adverse health effects ranging from sensory irritation to lung cancer caused by exposure to DPM. The method by which exposures are measured does not affect the conclusion that exposure to DPM produces serious adverse health effects. Comments concerning the analytical method are addressed in part VIII.A. Section 57.5060(b), addressing the final limits.

B. Exposures to DPM in Underground Metal and Nonmetal Mines

The 2001 risk assessment and the update presented in 2005 used the best available data on exposure to DPM at underground M/NM mines to quantify excess lung cancer risk. “Excess risk” refers to the lifetime probability of dying from lung cancer during or after a 45-year occupational DPM exposure. All of the exposure-response models for lung cancer are monotonic (i.e., increased exposure yields increased excess risk).

We evaluated exposures based on 355 samples collected at 27 underground U.S. M/NM mines prior to promulgating the 2001 rule. Mean DPM concentrations found in the production areas and haulageways at those mines ranged from about 285 μg/m

to about 2000 μg/m

, with some individual measurements exceeding 3500 μg/m

. The overall mean DPM concentration was 808 μg/m

. All of the samples considered in the 2001 risk assessment were collected prior to 1999.

Two sets of DPM exposure data, collected after promulgation of the 2001 final rule, were compiled for underground M/NM mines: (1) data collected in 2001 and 2002 from 31 mines for purposes of the 31-Mine Study (Table IV-1) and (2) data collected between 10/30/2002 and 10/29/2003 from 183 mines to establish a baseline for future sample comparisons (Table IV-2). The mean whole DPM concentration across all 358 valid samples in the 31-Mine Study was 432

DPM

μg/m

. The mean concentration across all valid 1,194 baseline samples was 318

DPM

μg/m

The relationship DPM ≉ TC/0.8 is the same as that assumed in the 2001 risk assessment. The relationship TC ≉ 1.3 × EC was formulated under the Second Partial Settlement Agreement, based on TC:EC ratios observed in the joint 31-Mine Study.

Table IV-1.—DPM Concentrations (μ

g/m

) by Mine Category for Samples Collected for the 31-Mine Study (2001-2002)

[DPM is estimated by TC ÷ 0.8]

Estimated 8-hour Full Shift Equivalent

DPM Concentration (μg/m

)

Metal

Stone

Trona

Other

No. of samples

116

105

Minimum

Maximum

2,581

1,845

331

1,210

Median

491

331

341

Mean

610

465

359

Std. Error

95% UCL

699

537

113

412

95% LCL

522

394

306

Table IV-2.—DPM Concentrations by Mine Category for Samples Collected During the Baseline Sampling Period (10/30/2002-10/29/2003)

[DPM is estimated by (1.3 × EC) ÷ 0.8.]

Estimated 8-hour Full Shift Equivalent DPM Concentration ( μg/m

)

Metal

Stone

Other N/M

Trona

Total

excluding Trona

No. of Samples

284

689

196

1,194

1,169

Maximum

2,532

3,724

1,200

509

3,724

Median

339

186

185

102

218

223

Mean

444

295

243

132

318

322

Std. Error

95% UCL

490

320

272

173

338

342

95% LCL

399

270

214

299

303

Thus, despite substantial improvements attained since the 1989-1999 sampling period addressed by the 2001 risk assessment, underground M/NM miners are still faced with an unacceptable risk of lung cancer due to their occupational exposure to DPM. The reader is referred to part D of this section, Significance of Risk, for further discussion of excess risk.

Personal exposure samples taken after October 2003 are collected according to our enforcement sampling policy. These enforcement samples collected after the end of the Baseline Sampling period are not representative of the

average

M/NM miner's exposure to DPM because we collect samples to target the highest risk miner, not the average miner. Therefore, this exposure information is not used to characterize the average miner's exposure to DPM. See section V.B, Economic Feasibility, for a summary of enforcement sampling results. However, our enforcement activities from November 1, 2003 through January 31, 2006 continue to show some miners have experienced exposures substantially greater than 308

μg/m

. During the time period from November 1, 2003 to January 31, 2006, 1,798 valid personal compliance samples from all mines covered by the regulation were collected. From these samples collected, 18% (324) of samples exceeded 308

μg/m

, 22% (396) exceeded 350

μg/m

, and 64% (1,151) exceeded 160

μg/m

. These percentages show that miners are still being exposed to high levels of DPM.

C. Health Effects

A key conclusion of the 2001 risk assessment was:

We have reviewed scientific literature pertaining to health effects of fine particulates in general and DPM in particular published later than what was considered in the 2001 risk assessment. This scientific evidence supports the 2001 risk assessment, and nothing in our review suggests that it should be altered.

A number of commenters endorsed the 2001 risk assessment, and suggested that the latest evidence strengthens its conclusions. Some other commenters responding to our 2003 NPRM jointly stated that “[t]he scientific evidence for the [adverse] health effects of DPM is overwhelming” and that “evidence for the carcinogenicity and non-cancer health effects of DPM has grown since 1998.”

A number of commenters contended that all of the evidence to date is insufficient to support limitation of occupational exposure to DPM. We believe that these commenters did not appreciate evidence presented in the 2001 risk assessment and/or mischaracterized its conclusions. For example, a few commenters erroneously stated that promulgation of the 2001 rule was based on only “two principal health concerns: (1) The transitory, reversible health effects of exposure to DPM; and, (2) the long-term impacts that may result in an excess risk of lung cancer for exposed workers.” Actually, as shown in the conclusion cited above, the 2001 risk assessment identified three different kinds of material health impairment associated with DPM exposure: (1) Acute sensory irritations and respiratory symptoms (including allergenic responses); (2) premature death from cardiovascular, cardiopulmonary, or respiratory causes; and (3) lung cancer. Although the cardiovascular, cardiopulmonary, and respiratory effects were associated with acute exposure to DPM, commenters presented no evidence that any such effects were “transitory” or “reversible.” Nor did commenters present evidence that immunological responses associated with either short-term or long-term DPM exposure were “transitory” or “reversible.”

In addition, some commenters erroneously stated that “no [quantitative] dose/response relationship related to the PELs could be demonstrated by MSHA.” These commenters apparently did not appreciate the discussion of exposure-response relationships in the 2001 risk assessment (66 FR 5847-54) and failed, specifically, to note the quantitative exposure-response relationships shown for lung cancer in the two tables provided (66 FR 5852-53). Relevant exposure-response relationships were also demonstrated in articles by Pope et al. cited in the 2003 NPRM, which will be discussed further below.

Some commenters objected that the exposure-response relationships presented in the 2001 risk assessment did not justify adoption of the specific DPM exposure limits promulgated. These commenters mistakenly assume the limits set forth in the 2001 final rule were derived from an exposure-response relationship. As explained in 66 FR at 5710-14, the choice of exposure limits, while justified by quantifiable adverse health effects, was actually driven by feasibility concerns. The exposure-response relationships provided clear evidence of significant adverse human health effects (both cancer and non-cancer) at exposure levels far below those determined to be feasible for mining.

The additional scientific literature cited in the 2003 NPRM, the 2005 final rule and this 2006 final rule is meant only to update and supplement the evidence of health effects cited in the 2001 risk assessment. Although the

2001 risk assessment presented ample evidence to justify its conclusions, additional supplemental DPM health effects literature is reviewed in this document that became available after the 2001 risk assessment was published.

The following section summarizes additional studies submitted to the record. Our review focuses on the implications of these study results for the characterization of risk presented in MSHA's 2001 assessment. These study summaries are presented in three tables that correspond to the material health impairments identified in the 2001 risk assessment: (1) Respiratory and immunological effects, including asthma, (2) cardiovascular and cardiopulmonary effects, and (3) cancer. A fourth table focuses on a recent study about potential mechanisms of action for DPM. These tables describe the studies that some commenters and the agency felt were representative of the type of new information available since the completion of the 2001 assessment and the updated 2001 risk assessment, however, these tables are not to represent a comprehensive review of all information published about particulate matter.

(1) Respiratory and Immunological Effects, Including Allergenic Responses

In the 2001 risk assessment, acute sensory irritations with respiratory symptoms, including immunological or allergenic effects such as asthmatic responses, were grouped together. Similar material health impairments likely to be caused or exacerbated by excessive exposures to DPM were identified. This finding was based on human experimental and epidemiological studies and was supported by experimental toxicology. (For an explanation of what type of health effects are considered by us to be material impairments of health, the reader is referred to the 2001 risk assessment (See 66 FR 5766.)

Table IV-3 summarizes five studies dealing with respiratory and immunological effects of DPM and/or fine particulates in general that have been submitted to the record since the 2005 literature update to the 2001 risk assessment. The epidemiological studies by Hoppin (2004) and Pourazar (2004) provide additional support for the association between diesel exhaust exposure and development of asthma. Three of the studies, Gluck (2003), Stenfors (2004), and Behndig (2006), have also shown that exposures of human volunteers to diesel exhaust at levels below 160

μg/m

cause inflammation of the human respiratory tract.

Table IV-3.—Studies of Human Respiratory and Immunological Effects

Authors, year

Description

Key results

Behndig et al., 2006

15 healthy volunteers exposed to diesel exhaust or air (2 hours, diesel concentration measured as PM

: 100 μg/m

) Eighteen hours after exposure, the volunteers were assessed using bronchoscopy with bronchoalveolar lavage and endobronchial mucosal biopsy

Exposure to diesel exhaust at this concentration is sufficient to cause airway inflammation.

Gluck et al., 2003

Comparison of nasal cytological examinations of 136 customs officers involved solely in clearance of heavy-goods vehicles using diesel engines with examinations of 58 officers working only in offices. Examinations were performed twice a year over a period of 5 years. Measured diesel engine emission concentrations for the exposed group varied between 31 and 60 μg/m

The exposed group was found to have chronic inflammatory changes of the nasal mucosa, including goblet cell hyperplasia, increased metaplastic and dysplastic epithelia, and increased leukocytes while the unexposed group did not.

Hoppin et al., 2004

An association between diesel exhaust exposure and development of asthma is explored. The study evaluated the odds of wheeze associated with nonpesticide occupational exposures in a cohort of approximately 21,000 farmers in Iowa and North Carolina. Logistic regression models controlling for age, state, smoking, and history of asthma or atopy were applied to evaluate odds of wheeze in the past year

Driving diesel tractors was significantly associated with elevated odds of wheeze (odds ratio = 1.31; 95% confidence interval = 1.13, 1.52). The odds ratio for driving gasoline tractors was lower but significant at 1.11 (95% confidence interval = 1.02, 1.21). A duration-response relationship was observed for driving diesel tractors but not for driving gasoline tractors.

Pourazar et al., 2004

15 healthy volunteers were exposed to diesel exhaust or air for 1 hour. Diesel concentration was measured as PM10 at 300 μg/m

)

This level of diesel exposure caused a significant increase in expression of the cytokine interleukin-13 in the airways of these volunteers. Interleukin-13 is known to play a key role in the pathogenesis of asthma.

Stenfors et al., 2004

25 healthy volunteers and 15 mild asthmatics were exposed to diesel exhaust or air alone for two hours (diesel concentration measured as PM

at 108 μg/m

). At six hours after exposure, subjects underwent bronchoscopy with bronchoalveolar lavage and mucosal biopsies

Diesel exhaust exposure was documented to cause airways inflammation in healthy volunteers. Diesel exhaust exposure did not significantly worsen existing airways inflammation in the asthmatics, but did significantly increase airways expression of the important allergy-associated cytokine, interleukin-10.

Review Article on Respiratory and Immunological Effects Considered after the 2005 Final Rule

There is a progressive accumulation of evidence showing the inflammatory and immunologic effects of diesel exhaust particulate exposure plays a role in the development of allergies and asthma. The 2001 risk assessment and the update to the risk assessment describe in detail review articles addressing these effects. The most recent review by Riedl and Diaz-Sanchez (2005), summarized in Table IV-4, provides an overview of observational and experimental studies that link DPM and asthma.

Table IV-4.—Review Articles on Respiratory and Immunological Effects

Authors, year

Description

Key results

Riedl and Diaz-Sanchez, 2005

Review of evidence-based studies of the health effects of air pollutants on asthma, focusing on diesel exhaust particles (DEP)

Intact DEP and extracts of DEP induce reactive oxygen species production. DEP and particulate matter induce release of Granulocyte Macrophage-Colony Stimulating Factor and increase intracellular peroxide production.

The ultrafine particle fraction of diesel exhaust might also exert biologic effects independent of chemical composition through penetration of cellular components, such as mitochondria.

In its 2002 “Health Assessment Document for Diesel Engine Exhaust,” the Environmental Protection Agency (EPA) reached the following conclusion with respect to immunological effects of diesel exhaust:

Recent human and animal studies show that acute DE [diesel exhaust] exposure episodes can exacerbate immunological reactions to other allergens or initiate a DE-specific allergenic reaction. The effects seem to be associated with both the organic and carbon core fraction of DPM. In human subjects, intranasal administration of DPM has resulted in measurable increases of IgE antibody production and increased nasal mRNA for some proinflammatory cytokines. These types of responses also are markers typical of asthma, though for DE, evidence has not been produced in humans that DE exposure results in asthma. The ability of DPM to act as an adjuvant to other allergens also has been demonstrated in human subjects. (EPA, 2002)

Submissions to the rulemaking record since the 2005 final rule support our previous position that exposure to DPM is associated with the development of adverse respiratory and immunological effects.

(2) Cardiovascular and Cardiopulmonary Effects

In the 2001 risk assessment, the evidence presented for DPM's adverse cardiovascular and cardiopulmonary effects relied on data from air pollution studies in the ambient air. This evidence identifies premature death from cardiovascular, cardiopulmonary, or respiratory causes as an endpoint significantly associated with exposures to fine particulates. The 2001 risk assessment found that “[t]he mortality effects of acute exposures appear to be primarily attributable to combustion-related particles in PM

2.5

[

i.e.

, fine Particulate Matter] (such as DPM) * * *.”

There are difficulties involved in utilizing the evidence from such studies in assessing risks to miners from occupational exposure to DPM. As noted in the 2001 risk assessment,

First, although DPM is a fine particulate, ambient air also contains fine particulates other than DPM. Therefore, health effects associated with exposures to fine particulate matter in air pollution studies are not associated specifically with exposures to DPM or any other one kind of fine particulate matter. Second, observations of adverse health effects in segments of the general population do not necessarily apply to the population of miners. Since, due to age and selection factors, the health of miners differs from that of the public as a whole, it is possible that fine particles might not affect miners, as a group, to the same degree as the general population (66 FR 5767).

However,

Since DPM is a type of respirable particle, information about health effects associated with exposures to respirable particles, and especially to fine particulate matter, is certainly relevant, even if difficult to apply directly to DPM exposures (66 FR 5767).

One new study on cardiovascular and cardiopulmonary effects was added to the record. See Toxicological Effects in this section for a summary of this article.

The EPA concluded in its 2002 Health Assessment Document for Diesel Engine Exhaust that diesel exhaust (as measured by DPM) is “likely to be a human carcinogen.” Furthermore, the assessment concluded that “[s]trong evidence exists for a causal relationship between risk for lung cancer and occupational exposure to D[iesel]E[xhaust] in certain occupational workers” (Health Assessment Document for Diesel Engine Exhaust, EPA, 2002, Sec. 9, p. 20). The EPA's 2004 Air Quality Criteria Document for particulate matter (EPA, 2004b) describes a number of additional studies related to the cardiopulmonary and cardiovascular effects of PM

2.5

, including work published later than that cited in MSHA's 2003 NPRM (68 FR 48668). One of the summary conclusions presented in that document is:

Overall, there is strong epidemiological evidence linking (a) short-term (hours, days) exposures to PM

2.5

with cardiovascular and respiratory mortality and morbidity, and (b) long-term (years, decades) PM

2.5

exposure with cardiovascular and lung cancer mortality and respiratory morbidity. The associations between PM

2.5

and these various health endpoints are positive and often statistically significant. [EPA, 2004b, Sec. 9 p. 46]

Submissions to the rulemaking record since the 2001 final rule support our previous position that exposure to DPM is associated with the development of adverse cardiovascular and cardiopulmonary effects.

(3) Cancer Effects

The 2001 risk assessment concluded that DPM exposure, at occupational levels encountered in mining, was likely to increase the risk of lung cancer. The assessment also found that there was insufficient evidence to establish a causal relationship between DPM and other forms of cancer. This update contains a description of three human research studies and a literature review relating DPM and/or other fine particulate exposures to lung cancer.

Lung Cancer

Table IV-5 presents three human studies pertaining to the association between lung cancer and exposures to DPM or fine particulates submitted to the record after the 2005 update of the 2001 risk assessment was done.

Table IV-5.—Studies on Lung Cancer Effects

Authors, year

Description

Key results

Garshick et al., 2004

An evaluation of lung cancer mortality in 54,793 railroad workers ages 40-64 with 10-20 years of service in 1959. Based on evaluation of death certificates, subsequent mortality was assessed through 1996. Diesel-exposed workers such as engineers and conductors were compared to a referent group of less exposed workers such as ticket agents, station agents, signal-maintainers, and clerks

Railroad workers in jobs associated with operating trains had a relative risk of lung cancer mortality of 1.4 (95% confidence limits = 1.30-1.51). The authors did not think this association was due to uncontrolled confounding. No relationship was found between years of exposure and lung cancer risk. The authors discussed the potential for this to be due to factors such as a healthy worker survivor effect, lack of information on historical changes in exposure, and the potential contribution of coal combustion product before the transition to diesel locomotives.

Guo et al., 2004

Evaluation of lung cancer mortality in all working Finns born between 1906 and 1945 and participating in the national census of December 1970. Based on the reported occupation held for longest time and a national database of exposures for various occupations, a variety of exposures including diesel exhaust were estimated. Information about subsequent diagnosis of lung cancer during the period 1971 to 1995 was obtained from the Finnish Cancer Registry

After controlling for other exposures such as asbestos and quartz dust, only a slight excess of lung cancer was found in men aged 20-59 associated with diesel exhaust exposure. A parallel, but weaker, association was documented in women. The authors concluded that risk associated with diesel exhaust “was not consistently elevated” and speculated that this was the result of factors such as low exposures or confounding from unmeasured non occupational exposures.

Jarvholm et al., 2003

Mortality study of Swedish construction workers. Information about occupation and smoking was taken from computerized health records available for the period 1971-1992. Workers in two occupations exposed to diesel exhaust, 6,364 truck drivers and 14,364 drivers of heavy construction vehicles were compared to a reference group of 119,984 carpenters and electricians

Truck drivers had significantly increased risk for cancer of the lung, while heavy construction vehicle operators did not. In heavy construction operators, a significant trend of decreased risk for lung cancer was associated with increasing use of vehicle cabins. The authors explained that there was a difference between truck and heavy equipment operators, but no conclusion could be reached without more detailed information about the duration and concentration of diesel exhaust exposures and smoking habits.

A Cohort Mortality Study With a Nested Case-Control Study of Lung Cancer and Diesel Exhaust Among Nonmetal Miners [NIOSH/NCI 1997]

A number of commenters expressed opinions on the unpublished document authored by Dr. Gerald Chase (2004) entitled

Characterizations of Lung Cancer in Cohort Studies and a NIOSH Study on Health Effects of Diesel Exhaust in Miners

. This document presents an analysis of some very preliminary data provided by NIOSH and the National Cancer Institute at a public stakeholder meeting held on Nov. 5, 2003. These data were taken from unpublished charts that NIOSH and NCI used to inform the public of the status and progress of their ongoing project,

A Cohort Mortality Study with a Nested Case-Control Study of Lung Cancer and Diesel Exhaust Among Nonmetal Miners

(NIOSH/NCI Study 1997). We previously addressed Dr. Chase's analysis in our 2005 final rule (70 FR 32906). NIOSH and NCI researchers involved in that project have not yet published their analyses or conclusions based on these data. When the study is concluded, we will assess the results and their association to our updated 2001 risk assessment findings. Therefore, the Agency believes that the opinions expressed by commenters on Dr. Chase's unpublished analysis of preliminary data are inappropriate for identifying or assessing the relationship between occupational DPM exposure and excess lung cancer mortality in that data set.

Bladder Cancer and Pancreatic Cancer

No additional information was submitted to the rulemaking record that would change our position that bladder cancer is associated with exposure to DPM. The Agency has not received additional information that would change our position that there is insufficient evidence to support a link between exposure to DPM and pancreatic cancer.

(4) Toxicological Effects of DPM Exposure

Table IV-6 presents one new particulate matter toxicity study (Sun et al., 2005) obtained since the 2005 final rule. The table identifies the agent(s) of toxicity investigated and indicates how the results support the risk assessment by categorizing the toxic effects and/or markers of toxicity found in each study.

Table IV-6.—Study On Toxicological Effects of DPM Exposure

Authors, year

Description

Key results

Agent(s) of toxicity

Toxic

effect(s)*

Limitations

Sun et al., 2005

Assessment of effects of subchronic exposure to environmentally relevant particulate matter on atherosclerosis and vasomotor tone in a mouse disease model

Long-term exposure to low concentration of PM

2.5

altered vasomotor tone, induced vascular inflammation, and potentiated atherosclerosis

Concentrated PM

2.5

from northeastern regional background particulate

Inflammation, Adverse cardiovascular effects

Exposure not specific to DPM.

No new review articles on various aspects of the scientific literature related to mechanisms of DPM toxicity were submitted to the record since the 2005 final rule. In summary, the peer-reviewed publications submitted to the rulemaking record addressing the health effects of exposure to diesel exhaust support our 2001 risk assessment (66 FR 5526; 30 CFR Part 2005) and nothing in our review suggests that it should be altered.

D. Significance of Risk

Adverse Health Effects

The first principal conclusion of the 2001 risk assessment was:

We agree with commenters who characterized the weight of evidence from the most recent scientific literature and the comprehensive scientific literature reviews carried out by other institutions and government agencies as supporting and potentially strengthening this conclusion.

In 2002, for example, the U.S. EPA, with the concurrence of its Clean Air Scientific Advisory Committee (CASAC), published its Health Assessment Document for Diesel Engine Exhaust (EPA, 2002). With respect to sensory irritations, respiratory symptoms, and immunological effects, this document concluded that:

At relatively high acute exposures, DE [diesel exhaust] can cause acute irritation to the eye and upper respiratory airways and symptoms of respiratory irritation which may be temporarily debilitating. Evidence also shows that DE has immunological toxicity that can induce allergic responses (some of which are also typical of asthma) and/or exacerbate existing respiratory allergies. [EPA, 2002]

In 2003, the World Health Organization (WHO) issued a review report on particulate matter air pollution and health. WHO concluded that “fine particles (commonly measured as PM

2.5

) are strongly associated with mortality and other endpoints such as hospitalization for cardiopulmonary disease, so that it is recommended that air quality guidelines for PM

2.5

be further developed.” (WHO, 2003)

In the 10th edition of its Report on Carcinogens, the National Toxicology Program (NTP) of the National Institutes of Health formally retained its designation of diesel exhaust particulates as “reasonably anticipated to be a human carcinogen.” (U.S. Dept. of Health and Human Services, 2002) The report noted that:

Diesel exhaust contains identified mutagens and carcinogens both in the vapor phase and associated with respirable particles. Diesel exhaust particles are considered likely to account for the human lung cancer findings because they are almost all of a size small enough to penetrate to the alveolar region.

* * * Because of their high surface area, diesel exhaust particulates are capable of adsorbing relatively large amounts of organic material * * * A variety of mutagens and carcinogens such as PAH and nitro-PAH * * * are adsorbed by the particulates. There is sufficient evidence for the carcinogenicity for 15 PAHs (a number of these PAHs are found in diesel exhaust particulate emissions) in experimental animals. The nitroarenes (five listed) meet the established criteria for listing as “reasonably anticipated to be a human carcinogen” based on carcinogenicity experiments with laboratory animals. [U.S. Dept. of Health and Human Services, 2002]

Although many commenters agreed that the adverse health effects associated with miners' exposure to DPM warranted an exposure limit, commenters from trade associations and industry continued to challenge the conclusions of the 2001 risk assessment. Discussions addressing this issue were summarized in the 2001 risk assessment and the 2005 update. As referenced in this section, the U.S. Environmental Protection Agency, World Health Organization, and the National Toxicology Program regard DPM exposure as adversely affecting human health.

Statement of Excess Lung Cancer Risk

In our 2001 risk assessment, we explained why we focused our quantification of health effects on lung cancer only. We estimated lower bounds on the significance of risks faced by miners occupationally exposed to DPM with respect to (1) acute sensory irritations and respiratory symptoms or (2) premature death from cardiovascular, cardiopulmonary, or respiratory causes. We expect the final rule to significantly and substantially reduce these two kinds of risk as well as (3) lung cancer. However, we were unable, based on available data, to quantify with confidence the reductions expected for the first two kinds and are still unable to do so. Therefore, MSHA's quantitative assessment of the rule's impact on risk is restricted to its expected impact on the third kind of risk—the risk of lung cancer (66 FR 5854).

In the 2001 risk assessment, MSHA assumed that, in the absence of this rule, underground M/NM miners would be occupationally exposed to DPM for 45 years at a mean level of 808 μg/m

, and estimated reductions in lifetime risk expected to result from full implementation of the rule, based on the various exposure-response relationships obtained from Sa

verin

et al.

(1999), Steenland

et al.

(1998), and Johnston

et al.

(1997).

Miner's exposures to DPM levels have declined since 1989-1999. We expect that further improvements will continue to significantly reduce the health risks identified for miners. There is clear evidence of adverse health effects due to exposure to DPM in the rulemaking record, not only at pre-2001 exposure levels but also at the generally lower levels currently observed at many underground mines. The adverse health

effects associated with exposure to DPM are material health impairments as specified under section 101(a)(6)(A) of the Mine Act.

Because the exposure-response relationships used in the risk assessment are monotonic, we expect that industry-wide implementation of each final limit will significantly reduce the risk of lung cancer and other adverse health effects among miners. The 2001 risk assessment used the best available data on DPM exposures at underground M/NM mines to quantify excess lung cancer risk. “Excess risk” refers to the lifetime probability of dying from lung cancer during or after a 45 year occupational DPM exposure. This probability is expressed as the expected excess number of lung cancer deaths per thousand miners occupationally exposed to DPM at a specified mean DPM concentration. The excess is calculated relative to baseline, age-specific lung cancer mortality rates taken from standard mortality tables. In order to properly estimate this excess, it is necessary to calculate, at each year of life after occupational exposure begins, the expected number of persons surviving to that age with and without DPM exposure at the specified level. At each age, standard actuarial adjustments must be made in the number of survivors to account for the risk of dying from causes other than lung cancer. Occupational exposure is assumed to begin at age 20 and to continue, for surviving miners, until retirement at age 65. The accumulation of lifetime excess risk continues after retirement through the age of 85 years.

Table IV-7, taken from the 2001 risk assessment, shows excess lung cancer estimates at mean exposures equal to the final limit equivalent to 200 micrograms of DPM per cubic meter of air for eight hour shift weighted average. The eight exposure-response models for lung cancer used in the 2001 risk assessment were based on studies by Sa

verin

et al.

(1999), Johnston

et al.

(1997), and Steenland

et al.

(1998). Assuming that TC is 80 percent of whole DPM, and that the mean ratio of TC to EC is 1.3, the DPM limit of 200 μg/m

shown in Table IV-7 corresponds to the 160 μg/m

TC limit adopted under the present rulemaking.

Table IV-7.—Excess Lung Cancer Risk Expected at Specified DPM Exposure Levels Over an Occupational Lifetime

[Extracted from Table III-7 of the 2001 risk assessment]

Study and statistical model

Excess lung

cancer deaths

per 1,000

occupationally

exposed

workers

†

Final DPM Limit 200 μg/m

(160 μg/m

TC)

verin et al. (1999):

Poisson, full cohort

Cox, full cohort

Poisson, subcohort

Cox, subcohort

182

Steenland et al. (1998):

5-year lag, log of cumulative exposure

5-year lag, simple cumulative exposure

159

Johnston et al. (1997):

15-year lag, mine-adjusted

313

15-year lag, mine-unadjusted

513

†

Assumes 45-year occupational exposure at 1,920 hours per year from age 20 to retirement at age 65. Lifetime risk of lung cancer adjusted for competing risk of death from other causes and calculated through age 85. Baseline lung cancer and overall mortality rates from NCHS (1996).

As explained in the 2005 final rule, the exposure-response models shown are monotonic (i.e., increased exposure yields increased excess risk, though not proportionately so). Therefore, using our estimates of mean exposure levels, they all predict excess lung cancer risks somewhere above the final whole DPM limit of 200 μg/m

, or equivalently, 160

μg/m

. Thus, despite substantial improvements apparently attained since the 1989-1999 sampling period addressed by the 2001 risk assessment, underground M/NM miners are still faced with an unacceptable risk of lung cancer due to their occupational exposure to DPM.

V. Feasibility

Section 101(a)(6)(A) of the Mine Act requires the Secretary of Labor, in establishing health standards, to most adequately assure, on the basis of the best available evidence, that no miner will suffer material impairment of health or functional capacity over his or her working life. Standards promulgated under this section must be based upon research, demonstrations, experiments, and such other information as may be appropriate. MSHA, in setting health standards, is required to achieve the highest degree of health and safety protection for the miner, and as stated in the legislative history of the Mine Act, MSHA must consider the latest available scientific data in the field, the feasibility of the standards, and experience gained under this or other health and safety laws.

Though the Mine Act and its legislative history are not specific in defining feasibility, the Supreme Court has clarified the meaning of feasibility in the context of OSHA health standards in

American Textile Manufacturers' Institute

Donovan

(OSHA Cotton Dust), 452 U.S. 490, 508-09 (1981), as “capable of being done, executed, or effected,” both technologically and economically.

The legislative history to the Mine Act indicates Congress' intent for MSHA when considering feasibility and states:

While feasibility of the standard may be taken into consideration with respect to engineering controls, this factor should have a substantially less significant role. Thus, the

Secretary may appropriately consider the state of the engineering art in industry at the time the standard is promulgated. However, as the circuit courts of appeals have recognized, occupational safety and health statutes should be viewed as “technology forcing” legislation, and a proposed health standard should not be rejected as infeasible “when the necessary technology looms on today's horizon”.

AFL-CIO

Brennan

, 530 F.2d 109 (3d Cir. 1975);

Society of Plastics Industry

OSHA,

509 F.2d 1301 (2d Cir. 1975),

cert. denied

427 U.S. 992 (1975).

Similarly, information on the economic impact of a health standard, which is provided to the Secretary of Labor at a [public] hearing or during the public comment period, may be given weight by the Secretary. In adopting the language of [this section], the Committee wishes to emphasize that it rejects the view that cost benefit ratios alone may be the basis for depriving miners of the health protection which the law was intended to insure. The Committee concurs with the judicial constitution that standards may be economically feasible even though from the standpoint of employers, they are “financially burdensome and affect profit margins adversely” (

I.U.D.

Hodgson

, 499 F.2d 6a47 (D.C. Cir. 1974)). Where substantial financial outlays are needed in order to allow industry to reach the permissible limits necessary to protect miners, other regulatory strategies are available to accommodate economic feasibility and health considerations. These strategies could include delaying implementation of certain provisions or requirements of standards in order to allow sufficient time for engineering controls to be put in place or a delay in the effective date of the standard. S. Rep. No. 95-181, 95th Cong. 1st Sess. 21 (1977).

The “arbitrary and capricious test” is usually applied to judicial review of rules issued in accordance with the Administrative Procedure Act. The legislative history of the Mine Act further indicates that Congress explicitly intended the “arbitrary and capricious test” be applied to judicial review of mandatory MSHA standards. “This test would require the reviewing court to scrutinize the Secretary's action to determine whether it was rational in light of the evidence before him and reasonably related to the law's purposes.” S. Rep. No. 95-181, 95th Cong., 1st Sess. 21 (1977). In achieving the Congressional intent of feasibility under the Mine Act, MSHA may also consider reasonable time periods of implementation.

Ibid.

at 21.

In order to establish the economic and technological feasibility of a new rule, an agency is required to produce a reasonable assessment of the likely range of costs that a new standard will have on an industry, and an agency must show that a reasonable probability exists that the typical firm in an industry will be able to develop and install controls that will meet the standard.

United Steelworkers of America, AFL-CIO-CLC

Marshall,

(OSHA Lead) 647 F.2d 1189, 1273 (D.C. Cir. 1980).

Like, the Mine Act, the OSH Act contains the term “technology-forcing” with respect to standards setting. The D.C. Circuit Court also determined with respect to technological feasibility under the OSH Act that:

* * * “technology-forcing” under the OSH Act, means, at the very least, that OSHA can impose a standard which only the most technologically advanced plants in an industry have been able to achieve-even if only in some of their operations some of the time.

American Iron & Steel Institute

OSHA, supra,

577 F.2d at 832-835.

Since “technology-forcing” assumes that “an agency will make highly speculative projections about future technology, a standard is obviously not infeasible solely because OSHA has no hard evidence to show that the standard has been met. More to the point here, we cannot require OSHA to prove with any certainty that industry will be able to develop the necessary technology, or even to identify the single technological means by which it expects industry to meet the PEL. OSHA can force employers to invest all reasonable faith in their own capacity for technological innovation.

Society of Plastics Industries, Inc.

OSHA, supra

509 F.2d at 1309, and can thereby shift to industry some of the burden of choosing the best strategy for compliance.

United Steelworkers of America,

647 F.2d at 1266.

This same court found that proving economic feasibility presented different issues from that of technological feasibility, where it stated:

But when the agency has proved technological feasibility by making reasonable predictions about experimental means of compliance, the court probably cannot expect hard and precise estimates of costs. Nevertheless, the agency must of course provide a reasonable assessment of the likely range of costs of its standard, and the likely effects of those costs on the industry.

Ibid. at 1266.

A. Technological Feasibility

Courts have ruled that in order for a standard to be technologically feasible an agency must show that modern technology has at least conceived some industrial strategies or devices that are likely to be capable of meeting the standard, and which industry is generally capable of adopting.

Ibid.

(citing

American Iron and Steel Institute

OSHA,

(AISI-I) 577 F.2d 825 (3d Cir. 1978) at 832-35; and,

Industrial Union Dep't., AFL-CIO

Hodgson,

499 F.2d 467 (DC Cir.1974));

American Iron and Steel Institute

OSHA,

(AISI-II) 939 F.2d 975, 980 (DC Cir. 1991). A control may be technologically feasible when “if through reasonable application of existing products, devices or work methods with human skills and abilities, a workable engineering control can be applied” to the source of the hazard. It need not be an “off-the-shelf” product, but “it must have a realistic basis in present technical capabilities.” (

Secretary of Labor

Callanan Industries, Inc.

(Noise), 5 FMSHRC 1900, 1908 (1983)). The Secretary may also impose a standard that requires protective equipment, such as respirators, if technology does not exist to lower exposures to safe levels. See

United Steelworkers of America,

647 F.2d at 1269.

We have established that it is technologically feasible for the underground M/NM mining industry to reduce miners' exposures to the DPM final limits as prescribed in the final rule. Unlike the 2005 NPRM, we are phasing in the final limit of 160 Total Carbon micrograms per cubic meter of air (160

μg/m

) over a two-year period, due to the updated feasibility information in the rulemaking record. This updated feasibility information relates primarily to the wider availability of alternative fuels, and in particular biodiesel, improved filter technology, and the impending availability of EPA compliant 2007 on-road diesel engines. Consequently, on May 20, 2006, the initial final limit will be 308 micrograms of EC per cubic meter of air (308

μg/m

), which is the same as the existing interim limit; on January 20, 2007, the final limit will be reduced by 50 micrograms and will be a TC limit of 350

μg/m

; and on May 20, 2008, the final limit of 160

μg/m

will become effective. Note that the 350

μg/m

final limit and the 160

μg/m

final limit are established as TC-based limits in this final rule. It is our intention to convert these TC limits to comparable EC limits; however, developing appropriate conversion factors for these limits was beyond the scope of the current rulemaking. These TC limits will be converted to comparable EC limits through a separate rulemaking.

To meet the final DPM limits, mine operators will be able to continue to use existing available engineering control technology and various administrative control methods used in meeting the interim DPM limit. However, we are affording the mining industry the additional time from that provided under the 2001 final rule to work through their remaining implementation issues with DPM control technology and to gain access to alternative fuels and DPFs. The additional time will also allow mine operators, especially small mine operators, time to find effective approaches to utilizing available DPM

control technology so that they will be capable of meeting the standard. Altogether, the mining industry will have been afforded over seven years to institute control technology to reduce miners' exposures to the final DPM limit of 160

μg/m

. Our decisions in the final rule are based on our enforcement experience, along with information and data in the updated DPM rulemaking record, which includes the 2001 and 2005 DPM rulemaking records. The final rulemaking record lacks feasibility documentation to justify lowering the final DPM limit to 160

μg/m

at this time.

The existing requirement for methods of compliance will continue to be applicable to the final limits. To attain the final limits, mine operators are required to install, use, and maintain engineering and administrative controls to the extent feasible. When engineering and administrative controls do not reduce a miner's exposure to the DPM limit, the controls are infeasible, or controls do not produce significant reductions (defined in the 2005 rule (70 FR 32868, 32916) as at least 25% reduction in the affected miners' DPM exposures), operators must continue to use all feasible engineering and administrative controls and supplement them with respiratory protection. Though mine operators may choose to use an engineering control or an administrative control to reduce a miner's exposure, or a combination thereof, existing § 57.5060(d) prohibits a mine operator from using respiratory protection in lieu of feasible controls. When respiratory protection is required under the final standard, mine operators must establish a respiratory protection program that meets the specified requirements under existing § 57.5060(d) of the DPM standard.

MSHA emphasizes that DPM engineering and administrative controls may be feasible, and therefore be required by MSHA, even if controls do not reduce a miner's exposure to the DPM limit.

Under this rule, MSHA intends that feasible DPM controls must be capable of achieving a significant reduction in DPM. We also note that most of the practical and effective controls that are currently available, such as DPM filters, enclosed cabs with filtered breathing air, and low-emission engines will achieve at least a 25% reduction. Other controls such as ventilation upgrades or alternative fuel blends may achieve a 25% reduction, depending on exposure circumstances and the specific nature of the subject control. It should also be noted that reductions of less than 25% could be due to normal day-to-day variations in mining operations as opposed to reductions due to implementing a control technology. Thus, for mines that are out of compliance with the DPM final limits, controls would be required that attain compliance, or that achieve at least a 25% reduction in DPM exposure if it is not possible to attain compliance by implementing feasible controls. If engineering and administrative controls are not capable of reducing exposure to the limits in this final rule, and cannot reduce DPM exposures by at least 25%, we would not require the implementation of those controls. In such cases, we will require miners to be protected using appropriate respiratory protective equipment.

If a particular DPM control were capable of achieving at least a 25% reduction all by itself, we would continue to evaluate the costs of that individual control to determine its economic feasibility. If a number of controls could together achieve at least a 25% reduction, but no individual control, if implemented by itself, could achieve a 25% reduction, we will evaluate the total costs of all controls added together to determine their economic feasibility as a group. In determining whether a combination of controls is economically feasible, we will consider whether the total cost of the combination of controls is wholly out of proportion to the expected results. We will not cost the controls individually, but will combine their expected results to determine if the 25% significant reduction criterion can be satisfied. The concept of significant reduction is not new to the M/NM mining industry. MSHA's 2005 Compliance Guide includes the 25% significant reduction for determining feasibility.

At this time, we believe that this compliance approach coupled with the phased-in final limits provides mine operators with flexibility necessary to assure feasible compliance. This current enforcement approach results in feasibility of compliance for the industry as a whole with each of the phased-in limits contained in this final rule while protecting miners' health. However, we continue to acknowledge that compliance difficulties may be encountered at some individual mines, but on a much smaller scale than what we project if the final limit of 160

μg/m

became effective in May 2006. This primarily will be due to implementation issues and the cost of purchasing and installing certain types of controls at these mines.

Moreover, pursuant to existing § 57.5060(c), mine operators can apply to the District Manager for a special extension for additional time in which to meet the final limits, including the initial final limit of 308

μg/m

. Although we anticipate that special extensions and our traditional hierarchy of controls in enforcement will address some compliance issues, we envision that some miners will have to wear respiratory protection under the final limit of 160

μg/m

Based upon a review of enforcement data, we believe that a large portion of the mining industry will initially encounter implementation issues as they attempt to attain compliance with the final limits using engineering and administrative controls. However, we believe that most mine operators will be able to overcome these issues within the two-year period during which the final limits will be phased-in. For example, the wider use of high biodiesel content fuel blends, which can reduce DPM emissions by up to 80% or more, will be greatly facilitated by the significant increases in biodiesel fuel production that will occur in the United States over the next two years. The National Biodiesel Board reports that annual biodiesel production rose from 25 million gallons in 2004 to 75 million gallons in 2005. They also report that biodiesel plants that are either under construction at the present time or in the pre-construction phase will add another 847 million gallons of annual production capacity. A large portion of this added capacity will be on-line by 2008.

Another example of a recent development that will help enable mine operators attain our final DPM limit of 160

μg/m

by May 2008 is the impending availability of U.S. EPA 2007 on-road diesel engines. U.S. EPA 2007 on-road diesel engine standards have DPM emission limits that are about 90% lower than the current EPA limits allow. The DPM reduction will be attained through the use of DPFs. The DPFs will be part of the engine and vehicle when sold. For example, a new 2007 on-road pickup truck will have a DPF installed on the vehicle at the time of purchase. The 2007 on-road engines will be commercially available starting in early 2007.

In addition to the EPA 2007 on-road DPM standards, EPA also has new Tier 4 off-road standards that will reduce DPM about 90%. Tier 4 will be phased-in beginning in 2008. Similar to the 2007 on-road engines, a DPF will be installed on the engine and vehicle when purchased. Even though the EPA implementation dates of Tier 4 is after the date of the final limit, the DPF technology is being developed at this

time by the engine and filter manufacturers in order to be ready for the tier 4 standards. This current work will enhance the developments and availability of DPF systems that can be retrofitted to mining vehicles.

Although the emission limits for 2007 on-road engines were established some time ago, we had very little insight as to the strategies and technologies that the engine manufacturers would use to meet these limits. For competitive reasons, the engine manufacturers did not publicize their strategies or designs for complying with these EPA regulations. We were therefore uncertain as to whether any 2007 on-road compliant engines would be compatible with typical underground M/NM mine operational and production requirements, duty cycles, and maintenance practices, and thus, whether they could be readily used or adapted for use in underground M/NM mines.

With the first 2007 on-road engines scheduled for release in early 2007, however, we now have a much clearer picture of the technologies that will be incorporated into these engines. The predominant technology will be DPM filters which incorporate some form of active regeneration to accommodate any duty cycle, ranging from constant high-speed over-the-road trucks to light duty delivery vehicles and pickup trucks and SUVs in stop-and-go traffic conditions. As noted later in this section of the preamble, we are confident that such filter technology is suitable for application in underground M/NM mines. Therefore, we expect appropriate 2007 on-road engines to be readily usable or adaptable for use in underground M/NM mining equipment. These engines will begin to become available in early 2007, with more and varied models becoming available in subsequent months and years.

In the future, we project that the number of miners who will need to wear respiratory protection will decrease as mine operators learn more about effectively selecting, retrofitting, and maintaining DPFs, as they begin to use EPA compliant 2007 on-road engines with integral DPFs, and as mine operators in remote locations are able to gain easier access to alternative fuels, primarily biodiesel.

1. MSHA's 2001 Assumptions Regarding Compliance With the Final Concentration Limit

We stated in the proposed rule that the assumptions that we used in 2001 in support of our cost estimates included:

(a) Fifty percent of the fleet will have new engines (these new engines do not impact cost of the rule) * * * Moreover, due to EPA [Environmental Protection Agency] regulations, which will limit DPM emissions from engines used in surface construction, surface mining, and over-the-road trucks (the major markets for heavy duty diesel engines), the market for low tech “dirtier” engines will dry up * * *; (b) one hundred percent of the production equipment and about fifty percent of the support equipment will be equipped with filters; (c) about thirty percent of all equipment will need to be equipped with environmentally controlled cabs; (d) twenty three percent of the mines would need new ventilation systems (fans and motors); (e) forty percent of the mines will need new motors on these fans; and (f) thirty two percent of the mines will need major ventilation upgrades (66 FR 5889-90).

Furthermore, we concluded that it would not be feasible to require the metal and nonmetal sector, as a whole, to lower DPM concentrations further, or to implement the required controls more swiftly (66 FR 5888).

2. Reasons Why the 2001 Assumptions Were Questioned

Over the five years since the 2001 final rule was promulgated, both MSHA and the mining industry have gained considerable experience with the implementation, use, and cost of DPM control technology. We have reviewed this experience, and our own enforcement data, and other relevant information, and conclude that effective DPM controls sufficient to attain compliance with the DPM limits specified in this final rule will be feasible and commercially available to mine operators by May 2008. For example, in addition to currently available DPM controls such as environmental cabs with filtered breathing air, a variety of DPF systems, low-emission engines, upgraded ventilation, and alternative fuels, by May 2008, we believe mine operators will benefit from wider availability of alternative fuels, particularly biodiesel, improved filter technology, and the availability of EPA compliant 2007 on-road diesel engines and diesel powered equipment. As implementation issues are resolved, the most successful implementation strategies will be adopted by other mine operators, thereby speeding up compliance by the industry as a whole. For example, in 2004, we were aware of only one mine operator that was using a high biodiesel content fuel blend as a DPM compliance method. DPM levels measured in this mine were consistently greater than 200

μg/m

prior to the change to biodiesel fuel, compared to levels less than 100

μg/m

after the change-over. In the most recent enforcement sampling at this mine, all samples were less than 50

μg/m

. By late 2005, we were aware of at least four other mine operators that had learned from this experience and adopted this compliance strategy. Another example is the recently developed Diesel Particulate Reactor

(described later in this section of the preamble). This new technology has been successfully implemented by a large nonmetal mine operator. Reactors are currently installed on about 80% of the mine's fleet of roughly 50 pieces of diesel equipment with no installation, operation, or maintenance problems reported. These experiences demonstrate that even the more complex DPM control technologies can be successfully implemented by mine operators. As these successful experiences are shared throughout the mining industry, compliance by the underground M/NM mining industry as a whole by May 2008 will be greatly facilitated. The extended time specified in this final rule is necessary to address the implementation issues that the industry as a whole must overcome. However, as noted above, we believe these issues can be resolved within the extended compliance timeframes established in the final rule.

Several commenters quoted previous MSHA statements from the rulemaking record they believe support their position that the final DPM limit is technologically infeasible. A few quoted a passage from the 2005 final rule: “MSHA acknowledges that the current DPM rulemaking record lacks sufficient feasibility documentation to justify lowering the DPM limit below 308

μg/m

at this time” (70 FR 32916). However, these commenters did not include the statements that followed, which explained that we believed it was feasible for the industry as a whole to fully comply with the interim limit, but that at that time—June of 2005—attaining levels lower than 308

μg/m

was not feasible for the entire industry. In our 2005 NPRM, we indicated that a DPM limit lower than 308

μg/m

should not become effective before January 2007, at the earliest, due to concerns about implementation difficulties. It was our intention that mine operators would use the period of nearly 20 months from June 2005 through January 2007 and the subsequent phased-in timeframes proposed in the NPRM to overcome implementation challenges and attain compliance with the reduced limit.

Some commenters stated that any delay in the effective date for the final DPM limit was unjustified on either technological or economic grounds. A number of commenters said that our 2005 NPRM makes it clear that several technologies are available which, alone or in combination, would permit mines to meet the final limit. Doubts about whether all mines can do so in all operations, or doubts about whether current distribution networks for alternative fuels are as complete as may be necessary under the final rule, do not in these commenters' views detract from the conclusion that the final limit is feasible. According to these commenters, MSHA's search for certainty that all mines can comply at all times in all circumstances is a violation of its technology-forcing mandate. In response, the Mine Act does not mandate that MSHA standards must be technology-forcing.

Another commenter stated that no technological reason exists for granting industry an additional five years, on top of the five years they have already had, to install existing technology to protect workers.

Although technology currently exists for compliance with both the interim and final DPM limits, we conclude that implementation challenges and difficulties with this technology and the costs of implementing it in the M/NM mining industry affect feasibility. We have observed the difficult applications engineering challenges faced by a substantial number of mine operators in implementing these technologies. Consequently, these challenges have led us to determine that additional time is needed by the industry as a whole to feasibly meet the final limit.

Another passage that several commenters in opposition to the 2005 NPRM quoted, stated that:

When we established the 2001 final limit, we were expecting some mine operators to encounter difficulties implementing control technology because the rule was technology forcing. We projected that by this time, practical and effective filter technology would be available that could be retrofitted onto most underground diesel powered equipment. However, as a result of our compliance assistance efforts and through our enforcement of the interim limit, we have become aware that this assumption may not be valid. The applications engineering and related technological implementation issues that we believed would have been easily solved by now are more complex and extensive than previously thought (70 FR 53283).

Although we have evidence of successful applications of DPM controls in the rulemaking record and the proven effectiveness of various products, systems, and strategies for controlling DPM emissions and exposures, we believe that the implementation challenges presented by the industry warrant granting some additional time to attain full compliance with the final limit. We intend, however, for the mining industry to utilize this extra time to diligently move forward in achieving compliance with the final limits.

Some commenters quoted the decision of

Secretary of Labor

Callanan Industries, Inc.

(Noise), 5 FMSHRC 1900, 1908 (1983)), which addresses feasibility of an individual mine operator to comply with an MSHA exposure-based health standard. These commenters concluded that based on the current existence of alternative fuels and DPFs, that no delay in the final limit was justified. However, as noted above, based on present implementation issues, we have determined that additional time is needed by the mining industry, as a whole, to meet the final limits.

Some other commenters stated that they do not believe there is a “realistic basis in present technical capabilities,” [quoting

Callanan

]. These commenters believe that there is not an adequate array of mine worthy, technically feasible solutions that are readily available for implementation in underground metal and nonmetal mines. They believe that their conclusion is confirmed by MSHA's statement in the 2005 NPRM that, “effective control technology that will reduce exposures to the final limit is speculative at this time” (70 FR 53285).

We find these arguments made by some commenters not persuasive, because in the 2005 NPRM, we acknowledged that full compliance with the final DPM limit by the industry as a whole by the original effective date of January 2006 was unlikely to be feasible. Over the past five years, we have been working with all members of the M/NM mining community affected by this final rule. We believe that the industry has made tremendous progress and will continue to work through these feasibility challenges and that it will be feasible for the industry to comply by the dates established in this final rule.

We continue to conclude, based on experience gained under the existing DPM rule, that the applications engineering required to adapt advanced DPM control devices and systems to new and existing mining equipment, to introduce alternative fuels, to train miners on their proper installation, operation, inspection, maintenance, and repair, and to integrate new methods and work practices into complex mining processes will take more time than we originally anticipated. However, we find one commenter's position that suitable DPM controls are not readily available to not be persuasive. The rulemaking record contains evidence that mine worthy control technology is available, and includes a number of examples of the successful implementation of such controls in all types of M/NM underground mines. The preamble to this final rule expands on those available technologies, indicating as we have suggested previously, that as demand for these technologies grows, manufacturers will respond by increasing the availability of feasible control systems for use at underground M/NM mines.

We know that, when properly implemented, DPFs, environmental cabs, alternative diesel fuels, ventilation, and modern low emission engines are effective engineering controls for reducing DPM exposures in underground M/NM mines. They have all been successfully implemented at numerous mining operations to comply with the current interim limit. We know that when properly implemented, various administrative and work practice controls can also effectively reduce DPM exposures. Effective control technology, however, cannot be successful if mine operators are not diligent in resolving their unique implementation issues. Implementation issues vary from mine to mine, and what accounts for some mine operators being successful while others have had only limited success attaining DPM compliance primarily depends on the particular choices of controls selected, and the corresponding implementation strategies employed. Clearly, it is easier and cheaper to obtain compliance at some mines than at other mines, due to factors such as mine size, mining conditions, the amount, type, and age of diesel equipment in use, height and width of roadways, grades that must be traversed, elevation of the workings, remoteness of the mine, and so on.

A commenter expressed the need for DPM controls that are, “readily available for implementation in underground metal and nonmetal mines.” Although we believe the rulemaking record supports the conclusion that the required DPM controls are commercially available, as noted above, the additional time offered by this final rule to meet the final limit is necessary for the mining community as a whole to implement these DPM controls.

A commenter observed that “The ‘put a filter on it' solution, suggested in prior MSHA analysis as the primary mode of

compliance, is now acknowledged to be a very goal that is not often achievable.” This commenter goes on to say “Therefore, by implication, the compliance model used to estimate compliance feasibility, and costs in the PREA and FREA is suspect.”

Several other commenters also claimed that our technological feasibility determinations were based on predictions that retrofitting diesel equipment with exhaust filters would be the primary means of compliance, but that no such filters were commercially available at the time. We believe these commenters may not fully appreciate our position on technological feasibility in at least two key respects. First, we have never advised the industry that full compliance with either DPM limit would be a simple process of “[putting] a filter on it.” Rather, our feasibility determinations were based on the assumption that mine operators would choose the control or combination of controls that best suited the unique circumstances and conditions at their mine. In the preamble to the 2001 final rule (66 FR 5713), we said, “the best actions for an individual operator to take to come into compliance with the interim and final concentration limits will depend upon an analysis of the unique conditions of the mine.” In the same preamble (66 FR at 5859), we indicated that,

The final rule contemplates that an operator of an underground metal or nonmetal mine have considerable discretion over the controls utilized to bring down dpm concentrations to the interim and final concentration limits. For example, an operator could filter the emissions from diesel-powered equipment, install cleaner-burning engines, increase ventilation, improve fleet management, use traffic controls, or use a variety of other readily available controls. A combination of several control measures, including both engineering controls and work practices, may be necessary, depending on site specific conditions.

We expected mine operators would have had less difficulty in appropriately selecting and experimenting with technology applications than we had observed at many mines. Also, we expected mine operators to be able to more effectively address their maintenance and regeneration issues with DPFs, and would have had better access to alternative fuels. Our experience revealed that many mine operators did not fully resolve all the complex implementation issues that were encountered. Some operators simply removed the controls instead of working through these implementation issues.

The other aspect of our position on technological feasibility that these commenters may not fully appreciate is our position on current technological feasibility versus feasibility at a future date. They have assumed that because we acknowledged that it was infeasible to meet the final limit by May 20, 2006, that it is also infeasible to meet the final limit at a future date as required in the final rule. Again, our position is that we believe that additional time will be required for certain key technologies to become sufficiently diffused and available, and that the industry as a whole will require additional time under this final rule to successfully implement the necessary controls to attain compliance with the final phased-in limits.

We believe it will be feasible for the industry as a whole to implement the required controls and attain compliance with the phased-in DPM limits within the timeframes established in the final rule. For example, biodiesel production in the U.S. will increase dramatically over the next two years, making it increasingly easier for mine operators to gain access to a reliable supply of this alternative fuel. Also, EPA compliant 2007 on-road diesel engines will begin to become available in early 2007, and their availability will grow in the months and years to follow. We believe that the industry as a whole will be capable of attaining compliance with the final limits using these and other existing DPM control methods. We also believe that industry-wide compliance within the timeframes established in the final rule will not require the development of new technologies.

We believe that the three-step phase-in approach for establishing the DPM limits and the wider use of alternative fuels, improved filter technology, and EPA compliant 2007 on-road engines along with other engineering and administrative controls, will enable the underground M/NM mining industry as a whole to resolve lingering implementation challenges and difficulties relating to the 160

μg/m

final limit.

In our 2005 NPRM, we proposed that the final DPM limit be phased-in in five steps over a five-year period. The choice of five-years for the length of the phase-in period was based on our compliance assistance and enforcement experience that indicated that mine operators were encountering more significant implementation issues than originally anticipated. These issues affected a greater portion of the industry and presented greater challenges to resolve than we anticipated in the 2001 final rule. The five-year phase-in period was proposed based on the rate at which we observed these implementation issues being successfully addressed at that time by the industry as a whole. We believed this five-year timetable for phasing-in the final limit was reasonable, providing for feasible compliance by the industry as a whole while insuring substantial annual reductions in DPM exposure of miners. However, we asked for comments on whether this proposed five-year phase-in would be the appropriate timeframe for mine operators to attain the final DPM limit of 160

μg/m

. Some commenters provided information opposing the five-year phase-in, saying any delay was unjustified. Other commenters supported the five-year phase-in as an improvement from the original January 2006 deadline, but suggested that due to feasibility concerns, even more time would be needed to attain compliance. Other commenters have consistently maintained that controls sufficient to attain the final limit do not exist, so the timeframe for compliance is irrelevant. Other commenters provided information supporting a shorter phase-in of the final limit.

We now believe that the three step phase-in of the final limit over two years that is incorporated into this final rule is the most appropriate approach and phase-in time period that both provides for maximum protection of miners and is also technologically and economically feasible for the industry to achieve. This determination was based on our enforcement experience, the comments in the rulemaking record addressing feasibility, and other relevant technical information we have obtained since we issued the 2005 NPRM.

The key information that we relied on to reduce the timeframe from the originally proposed five-year phase-in of the final limit to the two-year phase-in incorporated into the final rule included wider availability of alternative fuels, particularly biodiesel, improved filter technology, and the impending availability of EPA compliant 2007 on-road diesel engines. As previously discussed, we were also encouraged by the accelerating rate at which effective DPM control technologies were being implemented by mine operators, for example, high temperature disposable diesel particulate filter (HTDPF) systems. We believed the development of these systems would fill a critical gap in available filter technology, as they are particularly well suited to filter the exhaust from small and mid-sized equipment having low to medium duty cycles that were not good candidates for passive regeneration filter systems, and

on which mine operators did not wish to implement active filter systems. These systems demonstrated high filtration efficiency for EC, and did not increase NO

emissions. However, when used in underground M/NM mines, these systems were subject to filter element damage due to occasional high temperature exhaust exposures. We are now confident that these systems can be used successfully in mining applications if a heat exchanger is placed upstream from the filter element in the vehicle's exhaust system. We have recently learned that purpose-built heat exchangers are now commercially available, either as separate units that can be retrofitted to an existing HTDPF system or as an integrated unit that combines a heat exchanger with a filter.

Another example is the impending availability of EPA compliant 2007 on-road diesel engines. As noted earlier in this section, these engines must reduce DPM emissions by about 90% compared to current models, and also must meet strict NOX standards. As recently as the fall of 2005, we could not be certain these new engines would be fully compatible with underground M/NM mine operational and production requirements, duty cycles, and maintenance practices. With the introduction of EPA compliant 2007 on-road engines less than 8 months away, we are now aware that the predominant technology that will be used by the engine manufacturers to comply with these requirements will be DPFs with provision for continuous or automatic active filter regeneration regardless of equipment duty cycle. As noted later in this section of the preamble, we are confident such DPFs can be implemented by mine operators. These DPFs typically have very high EC filtration efficiency approaching 99% or more, and the method of filter regeneration eliminates implementation issues relating to whether a particular machine's duty cycle is sufficiently severe to enable passive regeneration and the perceived logistical complications associated with active on-board or active off-board filter regeneration.

These recent developments and technologies, along with increased utilization of the other engineering and administrative controls that we have discussed throughout the remaking record, such as environmental cabs with filtered breathing air, ventilation upgrades, and a host of administrative control options, will enable the underground M/NM mining industry as a whole to resolve lingering implementation challenges and difficulties relating to compliance with the 160

μg/m

final limit by May 2008. We are confident compliance under the final rule can be attained by most mines regardless of size or the commodity produced, because none of these technologies are mine size or commodity dependent.

Regarding biodiesel, the National Biodiesel Board noted in their comments that the domestic annual production capacity of biodiesel fuel would increase by at least 100 million gallons between May 2005 and May 2006. Based on production statistics released on November 8, 2005 by the National Biodiesel Board (

http://www.nbb.org/resources/pressreleases/gen/20051108_ productionvolumes 05nr.pdf

) we also learned that biodiesel production and consumption in the United States grew 300% in one year, from 25 million gallons per year in 2004 to an estimated 75 million gallons per year by the end of 2005. Biodiesel plants currently under construction will add 329 million gallons of annual production capacity (

http://www.nbb.org/buyingbiodiesel/ producers_marketers/ProducersMap- Construction.pdf

), and plants in the pre-construction phase will add another 518 million gallons of annual production capacity (

http://www.nbb.org/ buyingbiodiesel/producers_marketers/ProducersMap-Pre-Construction.pdf

). Much of this added production capacity is expected to be on-line by 2008, and some of these plants are being, or will be built in areas of the country that are currently underserved by biodiesel production facilities, such as Wyoming, Montana, Washington, California, Colorado, and Texas in the west, and Tennessee, Kentucky, Pennsylvania, Virginia, North Carolina, and New York in the east. This expected increased availability of biodiesel fuel by 2008 supports our decision to phase-in the final DPM limits in three steps from 308

μg/m

in May 2006 to 350

μg/m

in January 2007 to 160

μg/m

in May 2008.

Increased use of these fuels is consistent with and in support of recent U.S. initiatives towards greater energy independence. On October 22, 2004, President Bush approved a tax credit for blenders of biodiesel as part of H.R. 4520, also known as the American Jobs Creation Act of 2004 (Pub. L. 108-357). The tax credit for biodiesel produced from agricultural feedstocks is equal to $0.01 per gallon per percentage biodiesel in the blended product, essentially erasing the price difference between biodiesel and standard petroleum-based diesel fuel. In the late summer and fall of 2005 and again in the spring of 2006, due to price swings in the market, the net cost of biodiesel, when the tax credit is applied, was less than the cost of standard #2 diesel fuel in many parts of the country. As noted in more detail later in this section of the preamble, biodiesel consumption is expected to grow as more product is produced, as its availability increases in presently underserved parts of the country, and as the price gap between biodiesel and standard diesel closes, or as has recently occurred, when biodiesel becomes cheaper than standard diesel.

Retrofit options for self-cleaning DPFs should increase as the manufacturers of these filter systems become assured of a reliable market both in underground mining and on diesel-powered equipment intended for surface applications. In addition, two manufacturers of synthetic high temperature disposable filters have updated their specification sheets (discussed further in this section) to advise mine operators of the exhaust gas temperature limitations when using these filters. In order to meet these exhaust gas temperature limits, mine operators can purchase commercially available heat exchanger systems that can lower the exhaust gas temperature before contact with the filter. This can allow application of this type filter to be expanded to a wider variety of machines, especially ones that have low to medium duty cycle.

The more stringent EPA 2007 on-road exhaust emission standards (

http://yosemite.epa. gov/opa/admpress.nsf/ b1ab9f485b098972852562e7004dc686/ f20d2478833ea3bd85256e 91004d8f90?OpenDocument

) that begin in 2007 for on-road diesel engines (

http://www.epa.gov/otaq/diesel.htm

) will lead to an additional 90 percent reduction in particulate emissions when fully implemented. In addition, the EPA is mandating a reduction of the sulfur content of diesel fuel to no more than 15 ppm beginning in mid year of 2006 for on highway diesel engines and 2010 for nonroad diesel engines. Use of this fuel will enable advanced DPM control technology that would otherwise have been inhibited by the use of higher sulfur content fuel. Note that biodiesel fuel already meets this 15 ppm sulfur content requirement. Use of newer equipment with cleaner engines will also increase as older equipment is retired from service.

We anticipate that the three-step two year phased-in approach to establishing the final DPM limit that is incorporated in this final rule will provide the needed time to resolve the logistical, operational, and market-based factors that make implementation of the final limit infeasible at this time for the

industry as a whole. In addition, this delay may decrease our 2001 projection of the cost of compliance with the rule. During this phase-in, we will continue to work with the Diesel Partnership (discussed below) and the mining industry to help facilitate resolution of DPF selection and implementation problems for the diverse metal and nonmetal mining environment.

3. Diversity of Underground Mines Affected by the 2001 Final DPM Concentration Limit

The M/NM mining industry has approximately 168 underground mines that use numerous pieces of diesel powered equipment, widely distributed throughout each mining operation. These mines employ an array of mining methods to produce commodities including metals such as lead, zinc, platinum, gold, silver, etc. Also, there are different types of nonmetal mines that produce stone products such as limestone, dolomite, sandstone, and marble. Other underground nonmetal mines produce clay, potash, trona, and salt. Not only do these mines vary in the commodities that they produce, but they also use different mine designs and mining techniques such as room and pillar mining and stope mining. Some of these mines are large, complex multilevel mines, while others are small adit-type mines.

Ventilation levels in these mines also vary widely. Many limestone mines have only natural ventilation with variable air movement, whereas trona mines have high ventilation rates to dilute and remove methane gas released during the mining process. There are also deep metal mines with multiple levels that have far less ventilation than that found in underground trona mines. Furthermore, many metal and nonmetal mines are located in remote areas of the country, at high altitudes, or are subject to extremely hot or cold environments.

Considering these factors as a whole, we have found that there is no

single

control technology that would be suitable and effective for all M/NM mines in significantly reducing current DPM levels to or below the 2001 final DPM concentration limit of 160

μg/m

by May 2006.

4. Work of the M/NM Diesel Partnership (The Partnership)

Since promulgation of the 2005 final rule, the Partnership has been engaged in on-going NIOSH diesel research. One project involves a contract issued to Johnson Matthey Catalyst to develop a system to control nitrogen dioxide (NO

) emissions from diesel-powered underground mining vehicles equipped with Johnson Matthey's Continuously Regenerating Trap (CRT®) system. This system promotes regeneration at lower temperatures and is widely used in urban bus applications. If the results of laboratory evaluations show that a system is suitable for use in underground mining, NIOSH would continue studying this control technology with a long-term field evaluation in an underground mine. The M/NM Diesel Partnership is continuing to investigate this and other DPF applications.

5. Remaining Technological Feasibility Issues

In January 2001, we concluded that technology existed to accurately sample for DPM with a TC method and to reduce DPM levels to the 160

μg/m

limit by January 2006 (66 FR 5889). In June 2005, we concluded that it was technologically feasible to reduce M/NM underground miners' exposures to the interim PEL of 308

μg/m

by using available engineering control technology and various administrative control methods. However, we acknowledged that compliance difficulties may be encountered at some mines due to implementation issues and the cost of purchasing and installing certain types of controls. Specifically, we indicated that implementation issues may adversely affect the use of DPFs to reduce exposures despite the results reported in NIOSH's Phase I Isozone Study.

A number of commenters expressed the view that our enforcement sampling experience demonstrates that both the interim DPM limit, and especially the final DPM limit are technologically infeasible. Some of these commenters stated that our sampling data published in our June final rule and on our web site demonstrates that 90% or more of the regulated industry cannot comply with the January 19, 2006 limit of 160

μg/m

We have carefully examined these comments, the data in the June final rule, and our more recent enforcement sampling data. We note first that the commenters were not questioning the validity of the sampling method or whether our sampling data are complete and representative. Our sampling and analytical methods have been validated by NIOSH, and our longstanding sampling strategy that focuses on miners we believe will experience the greatest exposures is fully consistent with good industrial hygiene practice. Second, in evaluating the sampling data we recognize that current DPM levels at many mines exceed the final limit. In the 2005 NPRM, we pointed out that, “* * * in 2002 and 2003, we found that over 75% of the underground mines covered by the 2001 final rule have levels that would exceed the final concentration limit of 160

μg/m

.” We are encouraged, nevertheless, that DPM levels across the industry have been steadily and significantly reduced from the levels observed prior to the promulgation of the 2001 rule, and they are continuing to go down. As we stated in the 2005 NPRM (70 FR 53283), DPM exposures in affected mines have declined from a mean of 808 DPM μg/m

(646

μg/m

equivalent) prior to the implementation of the standard, to a mean of 233

μg/m

based on current enforcement sampling. During the time period from November 1, 2003 to January 31, 2006, 1798 valid personal compliance samples from all mines covered by the regulation were collected. From these samples collected, 18% of samples exceeded the 308

μg/m

interim limit, and 64% exceeded the 160

μg/m

final limit. The fact that 64% of the enforcement samples collected from November 1, 2003 to January 31, 2006 are above 160TC μg/m

does not establish infeasibility of the standard. We expect that overexposures will continue to decline as operators install new equipment, address implementation issues with DPFs, make use of biodiesel fuel, and install cleaner engines. Thus by May 2008, we would expect operators to achieve full compliance.

Our experience reveals that little progress was made in reducing DPM levels across the industry until the interim DPM limit became effective. Once the interim limit became effective, mine operators implemented the controls they believed were necessary to attain compliance. Based on our experience with other health standards, we would not have expected the industry as a whole to have achieved compliance with the final limit before the compliance deadline. Further, as discussed throughout this section of the preamble, we believe sufficient technologically feasible DPM controls exist for the industry as a whole to comply with the final DPM limit within the prescribed regulatory timeframe in this final rule.

Commenters, acknowledging that some DPM levels at some mines currently exceed both the interim and final DPM limits, indicated that the existence of such overexposures was the primary justification for the rule. These commenters observed that the rulemaking process is long, cumbersome and costly and that there “would be little point in invoking it to require the

industry to do something it is already doing on its own.”

These commenters continued, “It is settled law that MSHA ‘can impose a standard which only the most technologically advanced [mines] have been able to achieve even if only in some of their operations some of the time.’ ”

United Steelworkers,

647 F.2d at 1264.

We realize that some commenters will disagree with our decision not to presently implement the final limit. However, we have carefully reviewed all comments and data and believe that a number of mines have made good faith attempts to implement control technology but need more time to make such technology work. It is not our intent to have a majority of the mining industry apply for special extensions, or for a significant number of miners to be overexposed to DPM and have to wear respirators. We stated in the 2005 NPRM that a significant number of overexposures may:

* * * lead to another problem by requiring a large number of miners to wear respirators until feasible controls are fully implemented. We have never had a standard that resulted in a significant percentage of the workforce being required to wear respiratory protection, and we are concerned about the impact on worker acceptance of the rule and about mine operators' ability to remain productive. We are interested in public comment on how many miners would need to wear respirators to comply with the 2001 final limit and proposed multi-year phase-in of the final limit, and whether in each case they would need to wear respirators for their entire work shift, whether this amount of respirator usage is practical, and any other comments or observations concerning this issue (70 FR 53285)

The commenters that referenced the OSHA

Lead

decision also presented the results of an extensive analysis of our DPM sampling and enforcement actions at 11 selected mines. According to these commenters, these data show that we are not adequately enforcing the interim DPM limit because there were 56 sample results that exceeded the interim DPM limit, but we issued only 24 DPM citations. These commenters further assert that our failure to enforce the interim limit provides encouragement for mine operators who have delayed the implementation of controls that are necessary to attain both the interim and final DPM limit.

These commenters did not provide information that indicated which mines were included in the commenter's analysis. However, assuming the commenters' numbers are accurate, there are three plausible reasons for the discrepancy between the number of samples exceeding the enforceable limit and the number of citations. First, the commenters indicate that the data for their analysis were gathered from the MSHA Data Retrieval System, which can be accessed from a link on the MSHA internet home page. The DPM sampling data contained in this database includes DPM samples obtained by our inspectors during the “baseline” sampling period prior to July 20, 2003. In accordance with provisions of the Second Partial Settlement Agreement, samples that exceeded the enforceable limit during the baseline sampling period were not subject to citation as long as the subject mine operator was exercising good faith efforts toward developing a DPM compliance strategy. Thus, the Data Retrieval System includes numerous overexposure sample results that were not citable because they pre-dated our full enforcement of the interim limit.

Second, our enforcement policy for DPM, which is posted on our M/NM DPM Single Source page, identifies certain situations where a normally citable overexposure to DPM will not prompt a citation. In one case, a citation will not be issued if the mine operator can demonstrate that controls that would normally be effective in attaining compliance with the limit have been ordered, and the affected miner is wearing a suitable respirator in the context of a compliant respiratory protection program. This situation is covered in question 24 in the enforcement policy:

24. If MSHA finds a miner overexposed to DPM and I have a valid purchase order for controls that have not been delivered to my mine site, will I be cited for a violation? No. If you can demonstrate to MSHA, through appropriate documentation such as purchase orders, that you are making reasonable progress toward implementing feasible engineering and/or administrative controls that have a reasonable likelihood of achieving compliance with the interim DPM limit within a reasonable timeframe, and you have implemented a respiratory protection program meeting the requirements of ANSI Z88.2-1969 that covers all affected miners, MSHA will not conduct compliance sampling of affected miners at that time. The inspector will return to the mine to verify that adequate progress is being made toward full implementation of controls and/or to conduct DPM sampling based on the completion timeframe established by the mine operator.

In the other case, if the mine operator has fully implemented all feasible engineering and administrative controls and the affected miner is wearing a suitable respirator in the context of a compliant respiratory protection program, no citation will be issued even if an exposure exceeding the limit is measured. This situation is covered in question 29 in the enforcement policy:

29. How will MSHA determine if a citation is warranted when evaluating whether I have implemented all feasible controls? Once you use and maintain all feasible engineering and administrative controls to reduce a miner's exposure, implement the required respiratory protection program and require the miner to use a respirator, you will be in compliance with § 57.5060(a), even though a miner's DPM exposure may continue to exceed the limit and a citation will not be issued. Keep in mind that feasibility is an MSHA determination. If the agency finds that you failed to install, use and maintain all feasible controls, or you failed to establish an appropriate respiratory protection program, you will be out of compliance.

Third, some samples that exceed the interim DPM limit may be resamples of previously cited overexposures. Our enforcement sampling practice requires that after an overexposure is cited, the mine operator is given the opportunity to implement engineering and/or administrative controls to reduce the subject miner's exposure to or below the enforceable limit. Once these steps have been taken, we resample the miner to confirm that controls have been successful in lowering the miner's exposure to or below the limit. On occasion, the resample is still over the limit, in which case, if the operator has made good faith efforts to apply normally effective controls, the citation will be extended so that additional controls can be implemented, followed by another resample.

Thus, due either to controls being on order, to issues relating to feasibility, or to resample that continues to exceed the DPM limit, and depending on other factors, we may not issue a citation even though a sample result represents a DPM overexposure. We intend to continue this enforcement practice under this final rule and will issue necessary compliance guidance.

Several commenters repeated earlier public comments regarding their views that previous technological and economic feasibility determinations are invalid because they were based partially on analyses conducted using a “flawed” computer simulation program. The economic feasibility issues are addressed latter in this section. The computer program in question, referred to as the DPM Estimator, is a Microsoft® Excel spreadsheet program that calculates the reduction in DPM concentration that can be obtained within an area of a mine by implementing individual, or combinations of engineering controls. This program was the subject of a Preprint published for the 1998 Society of Mining Engineers Annual Meeting

(Preprint 98-146, March 1998), and it was fully described in a peer reviewed article in a professional journal (Haney and Saseen, Mining Engineering, April 2000). Its algorithm is accurate, and we have not received comments that challenged the mathematical basis for its calculation.

Although this program was criticized as “flawed” by several commenters, few specific errors in the design or utilization of the program were offered. One commenter indicated that the

* * * computer model was based on invalid assumptions of the availability of filters that would fit the entire fleet of equipment in use, and assumptions of perfect ventilation conditions throughout the industry.

This commenter continues,

* * * no such filters were available commercially at the time of the MSHA prediction, nor when the 2001 rule was published, nor had any undergone testing.”

Regarding the issue of ventilation, this commenter stated that,

* * * the assumption of ‘The Estimator’ of perfect ventilation in mines did not exist in reality and the rule could not be declared feasible based on these incorrect assumptions.

This same commenter goes on to say that our technological feasibility determinations for all of our DPM rulemakings, from the original 2001 final rule to this rulemaking, are invalid because they are founded on analytical results obtained from the Estimator.

We have responded previously to both of these comments, and to many other criticisms of the Estimator. Regarding the availability of DPFs, we must emphasize that our DPM rules have always been performance oriented, and that mine operators have been given wide latitude to select DPM controls that were best suited to their unique circumstances and conditions. Neither the original 2001 rule nor this current final rule requires DPFs as the exclusive means of compliance with the DPM limit. The Estimator contains provisions for estimating the effect of applying DPFs, ventilation upgrades, low DPM engines, and other DPM controls on DPM levels in an area of a mine. At the time that we promulgated our 2001 final rule, however, we acknowledged our limited in-mine documentation on implementation of DPM control technology with issues such as retrofitting and regeneration of filters. Consequently, we committed to continue to consult with NIOSH, industry and labor representatives on the availability of practical mine worthy filter technology.

Regarding the same commenter's concerns that ventilation issues were handled inappropriately in the 31 Mine Study, we believe the commenter used the term “perfect ventilation,” when they may have meant perfect mixing of ventilation airflows. “Perfect ventilation” is a term with which we are unfamiliar. We have never used this term in this or any other rulemaking, and are unfamiliar with it in the context of mine ventilation engineering. “Perfect mixing,” in the context of ventilation systems, is a common technical term that refers to an idealized process in which two or more airflows of dissimilar composition join, and in which the composition of the composite airflow is an instant and homogonous mix of the input airflows. The issue of perfect mixing was raised by one of the same commenters in their public comments on the August 14, 2003 proposed rule on the interim DPM limit, and we responded in detail to these comments in the preamble to the 2005 final rule (70 FR 32920-32921).

The commenters believe that the Estimator's computations of DPM concentrations are valid only if engine emissions are perfectly mixed with the air flow, which they suggest does not occur in an actual mine. As discussed in the 2005 final rule preamble, these commenters make an erroneous assumption with respect to our utilization of the Estimator. The Estimator actually incorporates two independent means of calculating DPM levels: one based on DPM sampling data for the subject mine, and one based on the absence of such sampling data. Where no sampling data exist, the Estimator calculates DPM levels based on a straightforward mathematical ratio of DPM emitted from the tailpipe (or DPF, in the case of filtered exhaust) per volume of ventilation air flow over that piece of equipment. This is referred to in the Estimator as the “Column B” option for calculating DPM concentrations. The commenters” observation that the Estimator fails to account for imperfect mixing between DPM emissions and ventilating air flows is a valid criticism of the “Column B” option. For this and other reasons, the Estimator's instructions urge users to utilize the “Column A” option whenever sampling data are available.

In the “Column A” option, the Estimator's calculations are “calibrated” to actual sampling data. Whatever complex mixing between DPM emissions and ventilating air flows existed when DPM samples were obtained, are assumed to prevail after implementation of a DPM control. This is an entirely reasonable assumption, and in fact, there is no engineering basis to assume otherwise. Indeed, comparisons of “Column A” Estimator calculations and actual DPM measurements taken in mines before and after implementation of DPM controls have shown good agreement, indicating that Estimator calculations do adequately incorporate consideration for complex mixing of DPM and air flows when the “Column A” option is used.

The Estimator was originally developed with both the Column A and Column B options because at the time it was developed (1997), the specialized equipment required for reliable and accurate in-mine DPM sampling, such as the submicron impactor, was not widely available. Consequently, few mine operators were able to obtain the in-mine DPM sample data required for utilizing the Column A option. Though mine operators may continue to use the Estimator, we rely more on our in-mine documentation and enforcement experience on the feasibility of DPFs.

This background and detailed explanation on perfect mixing was provided in the preamble to the 2005 final rule (70 FR 32920). However, the comments we received on this subject for the instant rulemaking do not acknowledge or respond to the background and explanation we provided in the earlier preamble. The commenters simply restate their previous assertion that the Estimator is flawed because it assumes perfect ventilation, which as noted above, we believe was meant to refer to perfect mixing.

As we have maintained throughout this rulemaking, mine operators should determine the control or combination of controls that will be best suited to their mine-specific circumstances and conditions, and that controls need to be evaluated, selected, and implemented on a case-by-case and application-by-application basis. Nonetheless, based on our experience, observations, and the comments received from mine operators, we believe to attain the final DPM limit, many mine operators that are not yet using DPFs will have to start using them, and most mine operators that are already using DPFs to attain the interim limit will have to continue or increase their use to attain the final limit. The mining industry maintains that while some operators are using DPFs to control miners' exposures to the interim PEL, it is infeasible for them to further reduce miners' exposures through expanded use of DPFs. However, we maintain that feasibility difficulties encountered with the use of DPFs can be resolved within the prescribed timeframe offered in this

final rule, and that the greatest impediment to more widespread use of DPFs throughout the industry is the need to overcome implementation challenges and difficulties relating to specific pieces of mining equipment. For example, as the final limits become effective, some mines that were possibly using one or two DPFs on large horsepower haul trucks may have to install more DPF systems on other types of machines, such as loaders or support and utility equipment, in order to attain the final limit.

As discussed extensively throughout the rulemaking record and as we explained in detail in the 2005 NPRM, mine operators continue to prefer passive DPF regeneration systems over active regeneration systems. Passive regeneration is the process where the temperature of the exhaust gas produced by the engine is sufficiently high for a sufficient percentage of the working shift to burn off the collected DPM on the DPF. In order for passive regeneration to be a viable option, filter regeneration has to occur frequently enough to prevent the DPM that accumulates in the filter from causing backpressure on the engine that exceeds the engine manufacturer's backpressure specification. Passive regeneration is normally preferred by mine operators because the DPF will regenerate in the normal course of equipment operation, with no interruption to mine production activities and no equipment downtime required for filter regeneration. Also, passive regeneration occurs without the need for intervention by the equipment operator, and it does not require any special external equipment or facilities. However, many pieces of mining equipment do not have engine duty cycles that will presently support consistent passive regeneration. This problem will take more time for individual mine operators to resolve.

If a passive DPF loads up with DPM, but the exhaust temperature is not sufficient to ignite and burn off the accumulated DPM, the backpressure on the engine will increase. Prolonged engine operation in excess of the manufacturer's backpressure specifications can cause engine and DPF damage. Therefore, it is strongly recommended that when passive regeneration DPF systems are installed, a means for the machine operator to monitor the engine's exhaust backpressure should be included. Such a provision is important even on equipment where the normal duty cycle easily supports passive regeneration. For example, if a piece of equipment on which a filter normally passively regenerates is used temporarily for some other activity having a less severe duty cycle, the filter may not passively regenerate, and backpressure could build up. Likewise, if the subject equipment experiences a maintenance related problem that causes an increase in the level of “engine out” DPM emissions, the rate of DPM buildup in the filter could exceed the capacity of the filter to passively regenerate. In such cases, excessive engine backpressure could build up in less than a working shift. If the equipment is provided with a means for monitoring backpressure, and the equipment operator observes engine backpressure rising to excessive levels, corrective action can be taken before engine or filter damage occurs. Successful implementation of passive DPF systems has been reported where the mine operators have determined that a machine has sufficient exhaust gas temperature for passive regeneration and exhaust backpressure is being monitored.

If passive regeneration is infeasible due to an insufficient duty cycle, active regeneration may be a feasible alternative. Active regeneration depends on an external heat source for burning off the DPM collected in a filter. Some mine operators commented that it is not feasible for them to utilize active regeneration due to the physical size of filters, machine downtime, and/or the cost associated with building and equipping underground regeneration stations required for active DPF regeneration. We disagree that these factors render active regenerating DPF systems infeasible. As discussed throughout the rulemaking record, and later in this section of the preamble, filter size and machine downtime issues relate to implementation challenges and difficulties which can impact feasibility of compliance with the final limits. We believe these factors can usually be effectively addressed through proper system selection and deployment, as described below, which take time to effect. We also believe the deployment of an active DPF system is economically feasible under the prescribed time frames for the final limit. Economic feasibility is discussed in detail later in this section in this preamble.

Engine emissions and exhaust flows affect the size of the DPF that needs to be installed. These factors are important considerations for both passive and active regeneration. If the DPF is undersized for a particular application due to high DPM emissions or high exhaust flows, a passive or active DPF system may become overloaded, requiring the filter to be removed from service for regeneration. If such an interruption occurred mid-shift, it would typically have a greater negative effect on production than if it occurred at the end of a shift. Active regeneration DPF systems are normally sized so that the filter has sufficient capacity for the host vehicle to operate over its normal duty cycle for at least a full shift or longer. In some cases, especially when a machine with an older, high emission engine needs to be filtered, a filter having sufficient capacity to allow for a full shift of machine operation may be too large to fit in the available space on the machine. For this reason, most DPF manufacturers do not recommend DPF installation on older high emission engines. Some mine operators who have faced this dilemma have opted to compromise by installing a smaller filter. The result is DPM overloading. DPM overloading leading to excessive backpressure on the engine is the main problem that mine operators experience when the DPF installation is not correct for the application and duty cycle. Possible feasible corrective actions include utilizing a larger DPF or a lower DPM emission engine, or both. As noted later in this section of the preamble, installation of a new, low-emission engine, in addition to facilitating use of a reasonably sized DPF, can cut DPM emissions by up to 90% or more, and their greater operating efficiencies can reduce maintenance costs and lower fuel usage by 10% to 15% compared to older technology high emission engines.

Regarding commenters' concern about the physical size of DPFs, if the DPF for a particular piece of equipment is too large to handle or too large to fit in the space available on the equipment, the exhaust could be divided into two branches fitted with smaller sized filters on each branch, or as noted above, the engine could be replaced by one with lower DPM emissions that can be effectively filtered by a correspondingly smaller DPF.

Since 2001, a number of older, high DPM emitting engines have been replaced with new, low DPM emitting engines, either through direct engine replacement into existing equipment or through the acquisition of new equipment, but not as many as we predicted in 2001. From our enforcement experience, we believe this has occurred in mostly the larger horsepower engines, greater than 150 hp, in production equipment. This equipment is typically turned over more frequently because it has more severe duty cycles, is worked harder, and typically has a shorter life than smaller, lower horsepower support equipment. High horsepower production equipment also typically accounts for the greatest proportion of DPM produced in the

mine, so replacing these engines was the highest priority at most mines. Thus, the smaller engines normally found in support equipment often have older engines with higher DPM emissions per horsepower than the newer and larger production equipment.

We estimated in the 2001 final rule that 50% of the support equipment would probably need DPFs for compliance with the final limit (66 FR 5889-90). The higher DPM emissions from these engines, however, can complicate the expanded use of DPFs on this equipment. It is our belief that the mining industry will need additional time to further evaluate the proper sizing of both passive and active regeneration DPF systems on this equipment. Consequently, we expect the implementation issues relating to DPFs, particularly the selection of appropriate DPFs for a given application, regeneration issues, filter maintenance, etc. may extend over a larger portion of the mining industry as operators work toward compliance with the final limit.

Although we believe these implementation issues are sufficient to warrant the additional time offered in this final rule, we are nonetheless confident these issues can be effectively resolved within the compliance timeframes established in the final rule. For example, EPA compliant 2007 on-road engines will be provided with engine manufacturer supplied DPF systems that will regenerate continuously or automatically regardless of duty cycle, thereby greatly reducing implementation issues for the owner. Another example is the HTDPF with integral heat exchanger. This recently commercialized technology will enable filtering the exhaust from small to mid-size equipment with low to medium duty cycles. In addition to these and other new developments, competitive pressures will force the manufacturers of existing DPF systems to make incremental product improvements over time.

Note that high engine exhaust temperatures are an implementation issue only for disposal particulate filter element type DPFs. Ceramic and metallic filter element type DPFs can tolerate the normal range of exhaust temperatures from any diesel engine. In fact, passive regenerating DPFs depend on high exhaust temperatures to initiate the regeneration process. Where high exhaust temperatures could potentially occur, but where the user wishes to implement a disposal particulate filter element system, the use of a heat exchanger upstream from the filter element is required to lower the exhaust gas temperature and prevent filter element damage. For ceramic and metallic filter element type DPFs, heat exchangers are neither required nor desired.

Several commenters stated that we admitted to implementation problems with DPF systems in the preamble to the proposed rule. We agree with these commenters that we did express concerns about implementation issues with DPFs, and that these concerns, along with concerns about implementation issues with other DPM engineering controls led to our decision to propose delaying the effective date of the final limit of 160

μg/m

until January 2011. We continue to believe that a delay to the effective date for the final limit is necessary due to feasibility considerations. However, as we explained earlier in this section of the preamble, based on our enforcement experience and comments and other data in the rulemaking record addressing feasibility since we issued the 2005 NPRM, we have subsequently determined that delaying the final limit until 2011 is not justified. Primarily due to wider availability of alternative fuels, particularly biodiesel, improved filter technology, and the impending availability of EPA compliant 2007 on-road diesel engines, we believe the rulemaking record supports the three step phase-in of the final limit over two years, with the final limit of 160

μg/m

becoming effective in May 2008. This is the approach that is incorporated into this final rule, and we believe it provides for the maximum protection of miners that is technologically and economically feasible for the industry to achieve.

As discussed earlier in this section of the preamble, recent developments in the three key areas of biodiesel, improved filters, and EPA compliant 2007 engines, along with the application of a variety of other existing DPM controls, will enable compliance by the industry as a whole significantly sooner than was proposed in the September 2005 NPRM. Biodiesel, improved filters, and EPA compliant 2007 engines can be used by any size mine producing any M/NM commodity, and these technologies are not subject to many of the difficult implementation issues that have slowed the adoption of some DPM controls. For example, biodiesel can be used in any diesel engine with elastomeric fuel system components that are biodiesel compatible, and any non-compatible components can be easily replaced. No other engine or equipment modifications of any kind are required. Improved diesel particulate filters are commercially available for retrofit to any size diesel engine, and systems like the HTDPF and diesel particulate Reactor

are particularly well suited to installation on small and medium sized production and support equipment that had been problematic for some mine operators. No implementation issues in regards to selection of the DPF media, sizing, or regeneration type are expected for EPA compliant 2007 on-road engines. As discussed previously in this section, the engine will have a DPF installed in the vehicle when purchased by the mine operator.

DPF systems are a more effective control technology for reducing EC than TC. In order to comply with the final limit, we expected that most mine operators would need to add to the DPM controls they had previously implemented for compliance with the interim limit. We also anticipated that many mine operators that had successfully attained compliance with the interim limit without DPFs would need to utilize DPFs to obtain compliance with the final limit.

We acknowledged in previous preambles that DPFs may not be the optimal solution for all machines, especially machines equipped with dirtier engines. But we have also advised that machines with older, dirtier engines should be replaced or re-powered with cleaner engines, and then if necessary, be equipped with DPF systems.

We continue to emphasize to the mining industry to utilize our DPM Single Source Page to obtain information to assist with installation of DPF systems. This information stresses that DPFs require the engine to be maintained through a good maintenance program and to monitor the exhaust backpressure in order to prevent the DPF system from becoming overloaded with DPM. Minimizing these problems can help prevent premature DPF or engine failure, which affect feasibility.

NIOSH commented that

Although adverse health effects occur at the proposed concentration limits and below, NIOSH recognizes that all factors, including technical and economic feasibility must be considered by MSHA in developing an exposure standard. NIOSH is aware of the ‘implementation and operational difficulties’ currently facing the metal and nonmetal mining industry presented in MSHA's preamble, Section IV. Technological Feasibility (page 53282). A phase-in period may provide time to resolve such issues. Requiring control technologies before mine operators have had sufficient time to work through selection and implementation problems may create hazards and adverse health effects, such as the elevated levels of NO2 experienced when some PT-catalyzed

diesel particulate filters (DPFs) have been used in poorly or marginally ventilated areas.

NIOSH also recognizes that the mines covered by this proposed standard have unique designs and operational differences presenting unique challenges in controlling and reducing diesel emissions. For some metal and nonmetal mines, targeted reductions in exposures of underground miners to DPM below the 400 μg/m

TC or 308 μg/m

elemental carbon (EC) current limit may be achieved only through implementation of complex, integrated strategies and state-of-the-art control technologies.

The first steps to control diesel emissions are fundamental changes to improve mine ventilation and diesel engine maintenance practices, along with the introduction of cleaner engines or the use of alternative fuels, such as biodiesel, when practical. When these are insufficient to achieve compliance, more advanced diesel emission control technologies, such as DPF systems, may be necessary to achieve compliance.

We have considered the technological and economic feasibility of achieving the final limits specified in this final rule as discussed throughout this preamble. The three step phase-in approach allows mine operators more time to work towards implementation of DPM control technologies. We agree with NIOSH that the first steps that the mine operators took to lower DPM levels were changes to engines, maintenance practices, ventilation systems, and to a lesser extent, alternative fuels. As we have discussed in this preamble, these efforts have lowered miners' exposure to DPM as our enforcement sampling has shown.

Even though NIOSH refers to DPFs as “more advanced diesel emission control technologies,” some mines have already implemented DPFs in order to comply with the interim standard. These same mines will most likely continue using DPFs, plus add additional DPFs or other DPM controls such as biodiesel, to meet the final limits. However, we agree that the final limits will require a larger segment of the mining industry to implement DPFs and alternative fuels. We agree that underground metal and nonmetal mines present unique designs and operational differences which affect the application of DPM controls. This three step phase-in approach provides the time for mine operators to learn more about advanced control technologies with regards to implementation issues.

NIOSH further referenced a June 25, 2003 letter to the Assistant Secretary from Dr. John Howard, Director, NIOSH, relating to DPFs. NIOSH stated that although DPFs “* * * are commercially available, the successful application of these systems is predicated on solving technical and operational issues associated with the circumstances unique to each mine.” This three step phase-in of the final limits will provide the necessary time for mine operators to overcome these technical and operational issues, since we believe that DPFs are now more readily available and DPF implementation issues can be resolved.

This commenter also agreed with us that mine ventilation, maintenance, cleaner engines or use of alternative fuels, such as biodiesel were effective DPM control measures. However, the commenter stated that when these methods are insufficient to achieve compliance, more advanced control technologies would be needed, such as DPF systems. Gaining extensive experience with implementation and operation of DPF systems on production vehicles would greatly assist in resolving some of these issues. The commenter further stated that to ensure success of the phase-in period, individual mine operators or a consortium of mine operators or other partnerships should have compliance plans detailing their integrated approach to reducing DPM levels in terms of maintenance, ventilation, fuels, control technologies, retrofitting, and monitoring.

We agree with the commenter that the final limit does require mine operators to continue implementing the current controls needed to meet the interim concentration limit, however, in order to meet the final limit, more controls may need to be implemented. If DPF systems are needed, then the mine operator will need to continue work to properly install and maintain DPF systems to manufacturers' specifications.

Some commenters referred to the NIOSH Phase I and II studies, stating that they were successful in showing that the DPM controls, especially DPF systems, work in reducing DPM. However, these commenters believed that NIOSH did not provide reliable data to indicate that the selected filter technology would provide the necessary reductions of DPM in actual mining applications. We responded to the NIOSH Phase I and II studies in the 2005 final rule. We noted the successful DPM reductions that were achieved from the DPM controls, especially DPF, in the Isozone study of Phase I. We further reviewed the work done by NIOSH in the production area of the mine in Phase II. We maintain as we did in the preamble to the 2005 final rule that “the Phase II study helped to confirm existing agency data that shows that it is technologically feasible to reduce miners' exposures to DPM to 308

μg/m

interim PEL.” (70 FR 32928) The NIOSH work confirmed that DPFs can reduce DPM to MSHA's DPM limits. As stated previously, as the final limit is reduced over the time frame specified in this final rule, the mine operator can implement additional DPF systems (or other DPM control technologies) to further reduce the DPM exposure. The NIOSH Phase II study and MSHA's Greens Creek study as discussed in the June 6 preamble (70 FR 32928—32929) showed reductions in EC.

The same commenters stated that the Phase II study showed that the efficiencies of the DPF did not always agree with laboratory studies. However, the commenters failed to acknowledge that the comment was directed towards the DPF systems performing better than laboratory data, especially for EC reductions. We highlighted this finding from NIOSH's Phase II study in the preamble to our 2005 final rule (70 FR 32928).

Several commenters continued to state concerns with the use of catalyzed ceramic DPF systems due to increased NO

levels. We discussed this issue thoroughly in the preamble to the 2005 final rule (70 FR 32928-32929). We concluded then, and we believe the evidence is still persuasive, that the NO

issues discussed in the NIOSH Phase II studies were related to deficient ventilation in the areas where the testing occurred. The results of the Greens Creek study, which also evaluated heavily platinum catalyzed DPFs, showed a possible rise in NO

; however the small increase detected made it unclear as to the cause (preamble to the 2005 final rule, (70 FR 32884 and 32921)). Even if the NO

increases at Greens Creek were caused entirely by the catalyzed DPFs, the rise, which was about 1 ppm downstream from stopping operations involving one loader and two or three haulage trucks totaling over 1,000 horsepower, was manageable due to effective auxiliary ventilation. We continue to acknowledge that highly catalyzed platinum ceramic DPFs have the potential to generate higher levels of NO

than the baseline emissions from the subject diesel engine. However, when such DPFs are used in conjunction with proper ventilation, NO

has not increased to hazardous levels. As discussed previously in this section, NIOSH commented that increased NO

levels occurred in poorly or marginally ventilated areas with the use of some catalyzed DPFs.

Several commenters agree that progress has been made with the application of ceramic DPF systems that regenerate passively on larger

horsepower production machines. The DPF systems have been shown to be highly efficient in collecting DPM and mine operators have reported that they do passively regenerate on the larger horsepower, production machines. The production machines operate at a heavy duty cycle that corresponds to high exhaust gas temperatures for a sufficient portion of the shift. This allows the DPF to regenerate passively and burn off the collected DPM, thus keeping the DPF below the engine manufacturers' maximum allowable exhaust backpressure.

One mine operator provided a list of their DPF systems that have been in operation up to 9000 hours. The DPF systems were supplied by two different DPF manufacturers, but were both designed for passive regeneration. This commenter stated that 13 of their 17 haul trucks were equipped with passive regeneration DPFs and they are currently evaluating 4 more units on their haul trucks. According to the information submitted by this commenter, they have plans for installation of DPFs on 6 of their loaders. The commenter stated that the process of achieving DPF reliability has been arduous, and required much discussion and work with the DPF manufacturer.

Another mine operator also stated that 32 passive regeneration DPF systems have been installed with an average life of the DPF system from 3000-4000 hours. The operator stated that the success has been with haul trucks and they are working on evaluating the installation of this type DPF on LHD's.

Yet another mine reported installing four passive DPF systems on machines and the exhaust backpressure quickly exceeded the manufacturer's specification for exhaust backpressure. The commenter stated that the DPF would not passively regenerate, requiring the mine to remove them for cleaning.

The experiences described by these three mine operators continue to show that DPF system selection and installation must be carefully evaluated. However, overall it appears that a number of mine operators have been successful in installing passive regeneration DPF systems on machines that have high duty cycles and are therefore acceptable for passive regeneration, particularly haulage trucks and some loaders. We continue to advise mine operators that DPF systems that utilize passive regeneration must be carefully evaluated and well-maintained for their successful operation. Both MSHA and NIOSH continue to post extensive information on DPF systems on our respective Web sites. The Filter Selection Guide (detailed in the preamble to the 2005 final rule (70 FR 32922)) that was designed by NIOSH and MSHA continues to be an important tool for understanding the steps that must be taken to evaluate, select, and install a DPF system, especially one that depends on passive regeneration.

The same commenters also stated that when passive DPF systems were not feasible for some types of machines, especially those with medium to low duty cycles, they began evaluating active regeneration systems. In contrast to passive regeneration systems that depend on the high temperature of the engine's exhaust for burning off the DPM collected in the DPF, active systems use an external heat source to initiate the burning process for DPM. These commenters stated they have purchased some active systems for evaluation. However, they question the feasibility of utilizing active DPF systems in their mines due to a variety of logistical and operational concerns. For example, they point out that the mining production cycle at many mines does not provide for sufficient machine downtime to stop the machine and take it out of service in order to “plug” the machine into a regeneration station for regeneration of the DPF to occur. These commenters also stated that if they tried to change out DPFs, then the number of DPFs they would need to maintain on hand to store and rotate would be both cost prohibitive and storage space consuming. These commenters indicated that machines that return to the surface at the end of the shift would be candidates for active regeneration.

We agree that using active systems that require prolonged machine downtime for regeneration may not be feasible at all mines. However, at mines that only operate for a single shift or have a gap between shifts for blasting gases to clear, for example, regenerating active filters between shifts would be more feasible. For mines that operate around the clock, shutting down a key piece of production equipment for filter regeneration may present a problem. While such an implementation scheme would undoubtedly adversely affect mine production, the commenters did not provide information or data sufficient to establish the significance of the effect to determine the feasibility of the method.

More importantly, however, we have continued to recommend alternatives to this implementation scheme for active DPFs. For example, the fuel burner system regenerates the filter during normal equipment operations, without intervention by the equipment operator, and regardless of equipment duty cycle. Another option is to swap out filters instead of regenerating them on-board the equipment. Between shifts, a used filter can be removed from a piece of equipment and swapped for a regenerated filter. The used filter can then be placed in a regenerating appliance so it will be ready by the beginning of the next shift, and the equipment can be returned to duty without further delay. Using this implementation method, equipment downtime to accommodate DPF regeneration is measured in minutes rather than hours.

The technology for a variety of active systems continues to be commercially available. Implementation of active regeneration systems does require the mine operator to look at the logistics of time, place, and manpower to successfully perform the task. Those logistical decisions have been outlined in the NIOSH Filter Selection Guide. However, the mechanism for installation of a DPF system with active regeneration is less complex than passive regeneration because the location of the DPF on the machine, distance of the DPF from the exhaust manifold or turbocharger, and the orientation of the DPF are less important. On passive regeneration systems, the DPF must be as close as possible to the outlet of the exhaust manifold or turbocharger to utilize the maximum exhaust gas temperature. On active regeneration systems, this is not an installation requirement.

We continue to believe that for installation of either type of regeneration system, engine maintenance is vital. The engine must be maintained in good working condition. The engine must be maintained to limit excess DPM being emitted from unburned fuels or oil. Intake filters must be maintained and the engine's intake air restrictions and exhaust backpressure must be maintained to the manufacturer's specifications.

In addition, the exhaust gas backpressure measurement provides critical information on the amount of DPM loading on the DPF. Engine manufacturers and DPF manufacturers provide maximum limits that should not be exceeded to ensure proper engine and DPF operation. The exhaust backpressure ports and devices must be maintained. This has become a special concern in the underground coal sector, prompting the Coal DPM Partnership to form a Subcommittee to investigate the proper procedures to monitor backpressure and the proper type of equipment to use. MSHA and NIOSH

are working with labor and industry on this issue. Recommendations from this subcommittee will be shared with both coal and M/NM industry personnel since the information will be pertinent to both mining sectors involved with DPF systems. These recommendations will cover all types of DPF systems.

We believe that in place of ceramic DPF systems that require passive or active regeneration, machines could be installed with disposal DPF technology. These sy

This text is long and has been trimmed here. Open the source document for the complete record.

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.