Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners

Federal RegisterAug 14, 2003

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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:

Proposed rule; notice of public hearings; close of comment period; request for data.

SUMMARY:

This proposed rule would: Revise the existing diesel particulate matter (DPM) interim concentration limit measured by total carbon (TC) to a comparable permissible exposure limit (PEL) measured by elemental carbon (EC) which renders a more accurate DPM exposure measurement; increase flexibility of compliance by requiring MSHA's longstanding hierarchy of controls for its other exposure-based health standards at metal and nonmetal mines, but prohibit rotation of miners for compliance; allow MSHA to consider economic as well as technological feasibility in determining if operators qualify for an extension of time in which to meet the DPM limits; and simplify requirements for a DPM control plan. The proposed rule would also make conforming changes to existing provisions concerning compliance determinations, environmental monitoring and recordkeeping.

The existing final rule pertaining to “Diesel Particular Matter Exposure of Underground Metal and Nonmetal Miners,” was published in the

Federal Register

on January 19, 2001 (66 FR 5706, RIN 1219-AB11) and amended on February 27, 2002 (67 FR 9180). This rulemaking is part of a settlement agreement reached in response to a legal challenge to the January 19, 2001 diesel particular matter (DPM) standard.

Specifically in this proposal, MSHA intends to revise existing § 57.5060(a), limit on concentration of DPM; including designating elemental carbon as an appropriate surrogate for measuring the interim DPM limit; § 57.5060(c), addressing application and approval requirements for an extension of time in which to reduce the concentration of DPM; § 57.5060(d), addressing certain exceptions to the concentration limits; § 57.5060(e), prohibiting use of personal protective equipment to comply with the concentration limits; § 57.5060(f) prohibiting use of administrative controls to comply with the concentration limits, and § 57.5062, addressing the diesel particulate control plan. Also, MSHA intends to make conforming changes in this rulemaking to existing § 57.5061, addressing compliance determinations; § 57.5071, addressing exposure monitoring; and § 57.5075, addressing recordkeeping requirements.

MSHA has incorporated into the record of this rulemaking the existing rulemaking record, including the risk assessment to the January 19, 2001 standard. Commenters are encouraged to submit additional evidence of new scientific data related to the health risk to underground metal and nonmetal miners from exposure to DPM.

MSHA encourages mine operators to submit information in response to these provisions, including their current experiences with controlling miners' exposures to DPM.

In addition, under the terms of the settlement agreement, MSHA agreed to propose to change the existing DPM surrogate from total carbon to elemental carbon for both the interim DPM limit currently in effect and the final DPM limit that is applicable after January 19, 2006. In the Agency's Advance Notice of Proposed Rulemaking published on September 25, 2002 (67 FR 60199), MSHA notified the mining community that this rulemaking would revise both the interim concentration limit of 400 micrograms per cubic meter of air and the final concentration limit of 160 micrograms per cubic meter of air under § 57.5060 (a) and (b) of the existing standard. Some commenters to the ANPRM recommended that MSHA propose separate rulemakings for revising the interim and final DPM limits to give MSHA an opportunity to gather further information to establish a final DPM limit. The Agency agrees, and solicits information that would lead to an appropriate final DPM standard. The Agency will propose a separate rulemaking to amend the existing final concentration limit in the near future. With regard to the final DPM limit of 160 micrograms, MSHA requests comments on an appropriate final DPM limit.

DATES:

All comments on the proposed rule, including post-hearing comments, must be received by October 14, 2003. The public hearing dates and locations are listed in the Public Hearings section under

SUPPLEMENTARY INFORMATION.

Individuals or organizations wishing to make oral presentations for the record should submit a request at least 5 days prior to the hearing dates.

ADDRESSES:

Comments must be clearly identified as such and may be transmitted electronically to

comments@msha.gov,

by facsimile to (202) 693-9441, or by regular mail or hand delivery to MSHA, Office of Standards, Regulations, and Variances, 1100 Wilson Blvd., Room 2313, Arlington, Virginia 22209-3939. We intend to post comments on our website shortly after they are received.

Information Collection Requirements:

Comments concerning information collection requirements must be clearly identified as such and sent to both MSHA and the Office of Management and Budget (OMB) as follows:

(1) Send information collection comments to MSHA at the addresses above.

(2) Send comments to OMB by regular mail addressed to the Office of Information and Regulatory Affairs, Office of Management and Budget, New Executive Office Building, 725 17th Street, NW., Washington, DC 20503, Attn: Desk Officer for MSHA.

FOR FURTHER INFORMATION CONTACT:

Marvin W. Nichols, Jr., Director, Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson Blvd., Room 2313, Arlington, Virginia 22209-3939,

Nichols-Marvin@msha.gov,

(202) 693-9440 (telephone), or (202) 693-9441 (facsimile).

You can access this proposed rule and the Preliminary Regulatory Economic Analysis (PREA) at

http://www.msha.gov.

You can obtain these documents in alternative formats, such as large print and electronic files, by contacting MSHA.

SUPPLEMENTARY INFORMATION:

I. Public Hearings

The public hearings will begin at 9 a.m. and will end after the last scheduled speaker testifies. The hearings will be held on the following dates at the locations indicated:

Date

Location

Telephone

September 16, 2003

University Park Marriott, 480 Wakara Way, Salt Lake City, UT 84108

(801) 581-1000

September 18, 2003

Renaissance St. Louis Hotel Airport, 9801 Natural Bridge Road, St. Louis, MO 63134

(314) 429-1100

September 23, 2003

Hilton Pittsburgh, 600 Commonwealth Place, Pittsburgh, PA 15222

(412) 391-4600

The hearings will begin with an opening statement from MSHA, followed by an opportunity for members of the public to make oral presentations. You do not have to make a written request to speak. Speakers will speak in the order that they sign in. Any unallotted time will be made available for persons making same-day requests. At the discretion of the presiding official, the time allocated to speakers for their presentation may be limited. Speakers and other attendees may also present information to the MSHA panel for inclusion in the rulemaking record.

The hearings will be conducted in an informal manner. The hearing panel may ask questions of speakers. Although formal rules of evidence or cross examination will not apply, the presiding official may exercise discretion to ensure the orderly progress of the hearing and may exclude irrelevant or unduly repetitious material and questions.

A verbatim transcript of the proceedings will be included in the rulemaking record. Copies of this transcript will be available to the public, and can be viewed at

http://www.msha.gov.

MSHA will accept post-hearing written comments and other appropriate data for the record from any interested party, including those not presenting oral statements, prior to the close of the comment period on October 7, 2003.

II. Background

On January 19, 2001, MSHA published a final rule addressing diesel particulate matter exposure in underground metal and nonmetal mines (66 FR 5706, amended on February 27, 2002 at 67 FR 9180). The final rule established new health standards for underground metal and nonmetal mines that use equipment powered by diesel engines. The effective date of the rule was listed as March 20, 2001. On January 29, 2001, AngloGold (Jerritt Canyon) Corp. and Kennecott Greens Creek Mining Company filed a petition for review of the final rule in the District of Columbia Circuit Court of Appeals. On February 7, 2001, the Georgia Mining Association, the National Mining Association, the Salt Institute, and the Methane Awareness Resource Group (MARG) Diesel Coalition filed a similar petition in the Eleventh Circuit. On March 14, 2001, Getchell Gold Corporation petitioned for review of the rule in the District of Columbia Circuit. The three petitions were consolidated and are pending in the District of Columbia Circuit. The United Steelworkers of America (USWA) intervened in the litigation.

While these challenges were pending, the AngloGold petitioners filed with MSHA an application for reconsideration and amendment of the final rule and to postpone the effective date of the final rule pending judicial review. The Georgia Mining petitioners similarly filed with MSHA a request for an administrative stay or postponement of the effective date of the rule. On March 15, 2001, MSHA delayed the effective date of the rule until May 21, 2001, in accordance with a January 20, 2001 memorandum from the President's Chief of Staff (66 FR 15032). The delay was necessary to give Department of Labor officials the opportunity for further review and consideration of new regulations. On May 21, 2001 (66 FR 27863), MSHA published a notice in the

Federal Register

delaying the effective date of the final rule until July 5, 2001. The purpose of this delay was to allow the Department of Labor the opportunity to engage in further negotiations to settle the legal challenges to this rule.

First Partial Settlement Agreement

As a result of a partial settlement agreement with the litigants, MSHA published two documents in the

Federal Register

on July 5, 2001 addressing the January 19, 2001 DPM rule. One document (66 FR 35518) delayed the effective date of § 57.5066(b) regarding the tagging provision of the maintenance standard; clarified the effective dates of certain provisions of the final rule; and included correction amendments.

The second document (67 FR 35521) proposed a rule to clarify §§ 57.5066(b)(1) and (b)(2) regarding maintenance and to add a new subparagraph (b)(3) to § 57.5067 regarding the transfer of existing equipment between underground mines. MSHA published these changes as a final rule on February 27, 2002 (67 FR 9180), with an effective date of March 29, 2002.

Under the first partial settlement agreement, MSHA also conducted joint sampling with industry and labor at 31 underground metal and nonmetal mines to determine existing concentration levels of DPM; to assess the performance of the SKC submicron dust sampler with the NIOSH Method 5040; to assess the feasibility of achieving compliance with the standard's concentration limits at the 31 mines; and to assess the impact of interferences on samples collected in the metal and nonmetal underground mining environment before the limits established in the final rule become effective. The final report was issued on January 6, 2003.

Second Partial Settlement Agreement

Settlement negotiations continued on the remaining unresolved issues in the litigation. On July 15, 2002, the parties signed an agreement that is the basis for this proposed rule. On July 18, 2002, MSHA published a notice in the

Federal Register

(67 FR 47296) announcing that the following provisions of the January 19, 2001 rule would become effective on July 20, 2002:

(a) § 57.5060(a), addressing the interim concentration limit of 400 micrograms of total carbon per cubic meter of air;

(b) § 57.5061, compliance determinations; and

The notice also announced that the following provisions of the rule would continue in effect:

(a) § 57.5065, Fueling practices;

(b) § 57.5066, Maintenance standards;

(d) § 57.5070, Miner training; and

(e) § 57.5075, Diesel particulate records, as they relate to the requirements of the rule that are in effect on July 20, 2002.

The notice also stayed the effectiveness of the following provisions pending completion of rulemaking:

(a) § 57.5060(d), permitting miners to work in areas where the level of diesel particulate matter exceeds the applicable concentration limit with advance approval from the Secretary;

(b) § 57.5060(e), prohibiting the use of personal protective equipment to comply with the concentration limits;

(d) § 57.5062, DPM control plan.

Finally, the notice outlined the terms of the DPM settlement agreement and announced MSHA's intent to propose specific changes to the rule, as discussed below.

On September 25, 2002, MSHA published an Advance Notice of Proposed Rulemaking (67 FR 60199) to revise the DPM rule. The comment period closed on November 25, 2002. MSHA received comments from underground metal and nonmetal mine operators, trade associations, organized labor, individual mine operators, public interest groups and individuals. A number of commenters from industry and labor requested that MSHA propose the final DPM limit at a later date to allow MSHA to obtain more data. Commenters suggested that the Agency needs to determine the efficiency of different filtration devices, the relationship between elemental carbon and total carbon, and the feasibility of a DPM exposure limit.

This proposed rule would revise existing § 57.5060(a), addressing the interim concentration limit for DPM and the surrogate for measuring DPM limit; § 57.5060(c), addressing application and approval requirements for an extension of time in which to reduce the concentration of DPM; § 57.5060(d), addressing certain exceptions to the concentration limit; § 57.5060(e), prohibiting use of personal protective equipment to comply with the concentration limits; § 57.5060(f) prohibiting use of administrative controls to comply with the concentration limits, and § 57.5062, addressing the diesel particulate control plan. MSHA is also proposing conforming changes to existing § 57.5061, addressing compliance determinations; § 57.5071, addressing exposure monitoring; and § 57.5075, addressing recordkeeping requirements.

MSHA solicits comments on these provisions, as well as on experiences with controlling miners' exposures to DPM. MSHA also encourages commenters to submit additional evidence or new scientific data related to the health risk of DPM exposure in underground metal and nonmetal mines.

III. The Final PEL

MSHA intends to propose a revision to the final DPM limit in § 57.5060(b) that would reflect an appropriate permissible exposure limit rather than a concentration limit and would change the surrogate from total carbon to elemental carbon. Although the final limit is not a part of this proposed rule, MSHA solicits comments on an appropriate final DPM limit.

IV. Executive Summary of the 31-Mine Study

The following is the executive summary from “MSHA's Report on Data Collected During a Joint MSHA/Industry Study of DPM Levels in Underground Metal And Nonmetal Mines” (31-Mine Study) signed by MSHA on January 6, 2003. The Preliminary Regulatory Economic Analysis (PREA) for this proposed rule is not based on the 31-Mine Study.

On January 19, 2001, MSHA published a final standard on exposure of underground metal and nonmetal miners to diesel particulate matter (DPM). The rule was to become effective 60 days later, however, prior to the effective date, the rule was challenged by industry trade associations and mining companies. The United Steelworkers of America (USWA) also intervened in the litigation. In June 2001, agreement was reached on some of the issues in dispute. The parties further agreed to conduct a study involving joint in-mine DPM sampling to determine existing concentration levels of DPM in operating mines and to measure DPM levels in the presence of known or suspected interferences. The goals of the study were to use the sampling results and related information to assess:

—The validity, precision and feasibility of the sampling and analysis method specified by the diesel standard (NIOSH Method 5040);

—The magnitude of interferences that occur when conducting enforcement sampling for total carbon as a surrogate for diesel particulate matter (DPM) in mining environments; and

—The technological and economic feasibility of the underground metal and nonmetal (MNM) mine operators to achieve compliance with the interim and final DPM concentration limits.

The parties developed a joint MSHA/Industry study protocol to guide sampling and analysis of DPM levels in 31 mines. The parties also developed four subprotocols to guide investigations of the known or suspected interferences, which included mineral dust, drill oil mist, oil mist generated during ammonium nitrate/fuel oil (ANFO) loading operations, and environmental tobacco smoke (ETS). The parties also agreed to study other potential sampling problems, including any manufacturing defects of the DPM sampling cassette.

Major conclusions drawn from the study are as follows:

—The analytical method specified by the diesel standard gives an accurate measure of the TC content of a filter sample and the analytical method is appropriate for making compliance determinations of DPM exposures of underground metal and nonmetal miners.

—SKC satisfactorily addressed concerns over defects in the DPM sampling cassettes and availability of cassettes to both MSHA and mine operators.

—Compliance with both the interim and final concentration limits may be both technologically and economically feasible for metal and nonmetal underground mines in the study. MSHA, however, has limited in-mine documentation on DPM control technology. As a result, MSHA's position on feasibility does not reflect consideration of current complications with respect to implementation of controls, such as retrofitting and regeneration of filters. MSHA acknowledges that these issues may influence the extent to which controls are feasible. The Agency is continuing to consult with the National Institute of Occupational Safety and Health, industry and labor representatives on the availability of practical mine worthy filter technology.

—The submicron impactor was effective in removing the mineral dust, and therefore its potential interference, from DPM samples. Remaining interference from carbonate interference is removed by subtracting the 4th organic peak from the analysis. No reasonable method of sampling was found to eliminate interferences from oil mist or that would effectively measure DPM levels in the presence of ETS with TC as the surrogate. Results and findings of the study are summarized below.

Sampling at 31 Mines

There are a number of methods that can measure DPM concentrations with reasonable accuracy when it is at high concentrations and the purpose is exposure assessment. These methods do not at this time provide the accuracy required to support compliance determinations at the concentration levels required to be achieved under the DPM rule. The NIOSH Method 5040 provides an accurate method of determining the total carbon content of a sample collected in any underground metal or nonmetal mine when the submicron impactor is used. MSHA's January 2001 regulation requires using total carbon (TC) as a surrogate for DPM because a consistent quantitative relationship has been established between total carbon concentrations and the concentration of DPM as a whole. TC concentrations measured during the study ranged from 13 to 2065 μ/m

, with a mean of 345 μ/m

. To put these sampling results into context, the interim concentration limit specified in the final rule, effective after July 19, 2002, is 400 micrograms of TC per cubic meter of air (μ/m

). The final concentration limit is 160 micrograms of TC per cubic meter of air (μ/m

), effective after January 19, 2006.

TC concentrations at the non-trona mines were four to five times higher than at the trona mines. TC concentrations measured using area samples were found to be 38 to 62 percent of the levels found using occupational or personal samples.

Interferences

The submicron impactor removes 94% of the mineral dust from DPM samples. Remaining carbonate interference, if any, is removed by subtracting the 4th organic peak

from the analysis. For typical gold mine samples, the interference from elemental carbon (graphite) would be less than 1.5 μ/m

. The use of the impactor also eliminates the need to acidify samples, including samples from trona mines. For typical non-acidified trona mine samples, the interference from bicarbonate would be less than 0.5 μ/m

. Overload of particulate matter on the impactor substrate to the filter was not observed.

Interference from drill oil mist was found on personal samples collected on the drillers and on area samples collected in the stope where drilling was being performed. Use of a dynamic blank did not eliminate drill oil mist interference. Tests to confirm whether oil mist from ANFO loading operations could be interference were not conclusive. Blasting did not interfere with diesel particulate measurements. MSHA found no reasonable method of sampling to eliminate interferences from oil mist when TC is used as the surrogate.

No reliable marker was identified for confirming the presence of ETS in an atmosphere containing DPM. Use of the impactor does not remove the ETS as an interferent. No reasonable method of sampling was found that would effectively measure DPM levels in the presence of ETS with TC as the surrogate.

Laboratory Analytical Procedures and Sampling Cassettes

Intra- and inter-laboratory analytical imprecision appear to be in line with other airborne contaminants monitored by MSHA and other regulatory agencies. Each of the samples collected in the study was analyzed twice for TC content. To do this, two standard punches were taken from each exposed and each unexposed (

i.e.

, control) filter. One punch was always analyzed using the same instrument in MSHA's laboratory. The second punch from the same filter was either analyzed in MSHA's laboratory using one of two different instruments or sent out to one of three other laboratories, NIOSH, Natlsco or Clayton.

The supplier has satisfactorily addressed concerns over possible manufacturing defects in the specialized SKC DPM sampling cassette. MSHA believes that the performance of this cassette will be adequate for compliance sampling purposes.

Technological Feasibility

Technological feasibility for mine operators to achieve compliance with the interim and final DPM concentration limits was assessed for the 31 mines in the study on a mine-by-mine basis using a computerized Microsoft® 7 Excel spreadsheet program called the Estimator, combined with sampling results from the 31 mines. The Estimator mathematically calculates the effect of any combination of engineering and ventilation controls on existing DPM concentrations in a given production area of a mine. The analyses were based on the highest DPM sample result obtained at each mine and all major DPM emission sources at each mine plus spare equipment.

MSHA, however, has limited in-mine documentation on DPM control technology. Moreover, these sampling results were obtained at a time that few mine operators had implemented controls to reduce DPM concentrations at the subject mines. As a result, MSHA's position on feasibility does not reflect consideration of current complications with respect to implementation of controls, such as retrofitting and regeneration of filters. MSHA acknowledges that these issues may influence the extent to which controls are feasible. The Agency is continuing to consult with the National Institute of Occupational Safety and Health, industry and labor representatives on the availability of practical mine worthy filter technology.

The study found that five mines were already in compliance with the interim concentration limit, and another two mines were already in compliance with the lower, final concentration limit. The Estimator predicted that eleven of the 31 mines could achieve compliance with both limits through installation of DPM filters alone. Ventilation upgrades were specified for only 5 of the 31 mines in this study, and then only to achieve the final concentration limit.

The Estimator predicted that compliance with the interim and final concentration limits would be possible without requiring major ventilation installations (new main fan, repowering main fan, etc.) or requiring environmental cabs as a means of controlling DPM at any of the 31 mines. Industry commenters questioned whether practical mine-worthy filters were available for all engine sizes and whether more expensive controls would be necessary.

Economic Feasibility

Yearly costs for complying with both the interim and final concentration limits were determined for each of the 31 mines in the study. Cost estimates included the purchase cost of DPM controls specified for that mine in the technological feasibility assessment, plus related installation and operating costs. The aggregate yearly cost for all 31 mines to comply with the interim limit was estimated to be $2.1 million. Compliance with the final limit was estimated to cost an additional $1.1 million (in 2002 dollars). The yearly total to comply with both the interim and final concentration limits was estimated to be $3.2 million. The estimated costs in this report are based on the accuracy of the Estimator as reported in Appendix A, and therefore, do not include consideration of current implementation complications that could increase compliance costs.

MSHA concludes that a regulation is economically infeasible if it would threaten an industry's viability or competitive structure. In rulemaking, economic feasibility, as well as technological feasibility, is not defined for individual firms, but for an industry. As a screening device, MSHA has historically questioned economic feasibility if yearly compliance costs equal or exceed one percent of an industry's annual revenues.

MSHA developed a rough estimate of annual mine revenues using each mine's annual employee work hours and the production value per employee hour for the commodity produced. Summing the individual revenue figures resulted in an estimate of total revenues for the 31 mines in the study of $1.8 billion in 2000.

On this basis, MSHA estimates that the 31 mines in the study would incur yearly costs equal to 0.12 percent of their annual revenues to comply with the interim concentration limit and additional yearly costs equal to 0.06 percent of their annual revenues to comply with the final concentration limit. To comply with both the interim and final concentration limits, the 31 mines would incur yearly costs equal to 0.18 percent of their annual revenues. Since estimated yearly compliance costs are less than the screening benchmark of one percent or more of annual revenues, the data in this report supports a finding that the interim and final concentration limits are economically feasible. Industry questions whether all costs for active filter regeneration were considered and whether the proper controls (that is, filters) were used in the cost analysis. In particular, industry questions whether compliance with the interim concentration limit would require some mine operators to make major ventilation upgrades in their mines.

V. Compliance Assistance

A. Baseline Sampling Summary

Under the DPM Settlement Agreement, MSHA agreed to provide compliance assistance to the metal and nonmetal underground mining industry for a one-year period from July 20, 2002 through July 19, 2003. As part of MSHA's compliance assistance activities, the Agency conducted baseline sampling of miners' personal exposures at every underground mine covered by the existing regulation. The results of this sampling were used by MSHA in this preamble to estimate current DPM exposure levels in these mines. These sampling results also assist mine operators in developing compliance strategies based on actual exposure levels. This compliance assistance sampling began in October 2002.

This section summarizes the analytical results of 885 personal DPM samples collected from 171 mines between October 30, 2002 and March 26, 2003 as part of a compliance assistance initiative. Eleven of the 885 samples were invalid samples due to abnormal sample deposits, broken cassettes or filters, contaminated backup pads, or instrument or pump failure. Table V-1 lists the frequencies of invalid samples within each commodity.

The mines that were sampled produce clay, sand, gypsum, copper, gold, platinum, silver, gem stones, dimension marble, granite, lead-zinc, limestone, lime, potash, molybdenum, salt, trona, and other miscellaneous metal ores. These commodities were grouped into

four general categories for calculating summary statistics: metal, stone, trona, and other nonmetal (N/M) mines. These categories were selected to be consistent with the categories used for analysis of data for the 31-Mine Study. Most commodities are well represented in this analysis (average of 5.1 samples per mine). Some of these mines, such as the gold mines, have an average of only 2.0 samples per mine. MSHA is conducting additional compliance assistance sampling at these mines, however, the results are not available for inclusion in this analysis. Table V-2 lists the number of samples for each category of commodity.

MSHA used the same sampling strategies for collecting baseline samples as it intends to use for collecting samples for enforcement purposes. These sampling procedures are described in the

Metal and Nonmetal Health Inspection Procedures Handbook (PH90-IV-4),

Chapter A, “Compliance Sampling Procedures” and Draft Chapter T, “Diesel Particulate Matter Sampling.” Chapter A includes detailed guidelines for selecting and obtaining personal samples for various contaminants. All personal samples were collected for the miner's full-shift regardless of the number of hours worked, and in the miner's breathing zone. For the 874 valid personal samples, 83% were collected for at least eight hours. Total and elemental carbon levels, as well as DPM levels, are reported in units of micrograms per cubic meter for an 8-hour full shift equivalent.

The equation used to calculate a 480-minute (8-hour) full shift equivalent (FSE) exposure of total carbon is Total Carbon Concentration =

EP14AU03.000

Where:

EC = The corrected elemental carbon concentration measured in the thermal/optical carbon analyzer

OC = The corrected organic carbon concentration measured in the thermal/optical carbon analyzer

A = The surface area of the deposit on the filter media used to collect the sample

Flow Rate = Flow rate of the air pump used to collect the sample measured in Liters per minute

480 minutes = Standardized eight-hour workshift

All levels of carbon or DPM are reported in 8-hour full shift equivalent (FSE) total carbon concentrations measured in μg/m

Because personal sampling was conducted and no attempt was made to avoid interference from cigarette smoke or other organic carbon sources, total carbon was also calculated using the formula prescribed in the DPM settlement agreement:

Total Carbon Concentration = EC × 1.3.

MSHA agreed to use the lower of the two values (EC × 1.3 or EC + OC) for enforcement until a final rule is published reflecting EC as the surrogate.

MSHA collected DPM samples with SKC submicron dust samplers that use Dorr-Oliver cyclones and submicron impactors. The samples were analyzed either at MSHA's Pittsburgh Safety and Health Technology Center, Dust Division Laboratory or at the Clayton Laboratory using MSHA Method P-13 (NIOSH Analytical Method 5040,

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition,

September 30, 1999) for determining the total carbon content. Each sample was analyzed for organic, elemental, and carbonaceous carbon and calculated total carbon. Raw analytical results from both laboratories as well as administrative information about the sample are stored electronically in MSHA's Laboratory Information Management System.

If a raw carbon result was greater than or equal to 30 μg/cm

of EC or 40 μg/cm

of TC from the exposed filter loading, then the analysis was repeated using a separate punch of the same filter. The results of these two analyses were then averaged. The companion dynamic blank was also tested for the same analytes. Otherwise, an unexposed filter from the same manufacturer's lot was used to correct for background levels. In the event the initial total carbon result was greater than 100

μg/cm

, a smaller punch of the same exposed filter (in duplicate and corresponding blank) was taken and used in the analysis. Blank-corrected averaged results were used in the analysis when the sample was tested in duplicate.

Generally the lowest reporting limit is 3

μg/cm

. However, for this analysis, MSHA used all results below this limit. Due to variations in the analytical method, three samples have blank corrected elemental carbon results slightly below 0

μg/m

. This occurred because the corresponding blank filters have TC results slightly more than the exposed filter. Median values are not affected by the distribution of data and MSHA included them where appropriate.

The electronic records of the 885 samples that were available for analysis were reviewed for inconsistencies. Internally inconsistent or extreme values were questioned, researched, and verified. Although no samples were invalidated as a result of the administrative verification, eleven samples (1.2%) were removed from the data set for reasons unrelated to the values obtained. The reasons for invalidating these samples are listed in Table V-1. Accordingly, MSHA has included 874 samples from miners in the analyses. Table V-2 is a list of the number of valid samples by commodity.

Table V-1.—Reasons for Excluding Samples

Reason for excluding from analysis

Metal

Stone

Trona

Other N/M

Total

Abnormal Sample Deposit

Cassette/Filter Broken

Contaminated Backup Pad

Instrument Failure

Pump Failed

Total

Table V-2.—Number of Mines and Valid Samples, by Commodity

Commodity

Number of mines

Number of valid samples

Average number of valid samples by mine

Metal

189

5.3

Stone

109

519

4.8

Trona

5.0

Other N/M

151

6.6

Total

171

874

5.1

Table V-3 lists the number of samples collected by specific commodities at the time the data set was compiled (March 26, 2003) and sorted by the average number of samples per mine. Although MSHA made efforts to sample all underground metal and nonmetal mines covered by this rulemaking within the specified time frame, several mines have few or no samples for DPM in this analysis. Some metal and nonmetal mining operations are seasonal in that they are operated intermittently or operate at less than full production during certain times. These types of variable production schedules limited efforts to collect compliance assistance samples. MSHA continued to collect baseline samples during the compliance assistance period, especially at those mines with a low sampling frequency or where no samples were collected as of March 26, 2003. Future analyses will incorporate all subsequent valid samples.

Table V-3.—Number of Valid Samples per Mine for Specific Mines

Specific commodity

Number of mines

Number of samples

Average samples per mine

GEMSTONES MINING, N.E.C.

2.0

GOLD ORE MINING, N.E.C.

2.0

DIMENSION MARBLE MINING

3.0

LIMESTONE

3.0

TALC MINING

3.0

CRUSHED & BROKEN MARBLE MINING

4.0

GYPSUM MINING

4.0

CRUSHED & BROKEN STONE MINING, N.E.C.

4.6

CRUSHED & BROKEN LIMESTONE MINING, N.E.C.

413

4.9

CLAY, CERAMIC & REFRACTORY MINERALS MINING, N.E.C.

5.0

CONSTRUCTION SAND & GRAVEL MINING, N.E.C.

5.0

COPPER ORE MINING, N.E.C.

5.0

CRUSHED & BROKEN SANDSTONE MINING

5.0

HYDRAULIC CEMENT

5.0

LIME, N.E.C.

5.0

TRONA MINING

5.0

DIMENSION LIMESTONE MINING

5.5

LEAD-ZINC ORE MINING, N.E.C.

7.0

SALT MINING

7.0

MISCELLANEOUS METAL ORE MINING, N.E.C.

9.0

MOLYBDENUM ORE MINING

9.5

PLATINUM GROUP ORE MINING

10.0

POTASH MINING

10.0

SILVER ORE MINING, N.E.C.

10.7

AVERAGE OF ALL SAMPLES

171

874

5.1

There are 63 different occupations in underground metal and nonmetal mines represented in this analysis. The most frequently sampled occupations are Blaster, Drill Operator, Front-end Loader Operator, Truck Driver, Scaling (Mechanical), and Mechanic. Table V-4 lists the number of valid samples by occupation and commodity. Only occupations with 14 or more samples are listed. Occupations with fewer samples were aggregated for this table.

Table V-4.—Valid Samples, by Occupation and Mine Category

Occupation

Metal

Stone

Trona

Other N/M

Total

Truck Driver

121

183

Front-end Loader Operator

115

155

Blaster, Powder Gang

100

Scaling (mechanical)

Drill Operator, Rotary

Mechanic

Drill Operator, Jumbo Perc.

Mucking Mach. Operator

Utility Man

Scaling (hand)

Complete Load-Haul-Dump

Roof Bolter, Rock

Drill Operator, Rotary Air

Crusher Oper/Worker

All Others Combined

156

Totals

189

519

151

874

TC levels calculated by EC × 1.3 were lower than TC levels calculated by OC + EC in 663 (76%) of the 874 baseline samples. Of the 211 samples where TC = OC + EC was the lower value, 64% of the TC = EC × 1.3 values were within 12% of the TC = OC + EC value. Table V-5 summarizes the results of the baseline samples when determining the TC level using either EC × 1.3 or OC + EC. Approximately 6.3% of results did not concur when measuring TC by the two calculations. Approximately 15.7% of the samples were above the 400

μg/m

interim concentration limit when using TC = EC × 1.3 and approximately 19.5% were above the concentration limit when using TC = OC + EC. There is 93.7% concurrence between the two methods of calculating TC and comparing the calculations to the 400

μg/m

interim concentration limit.

Table V-5.—Comparison of Results With 400

μg/m

Calculating TC by OC + EC or EC × 1.3

All Valid Samples—OC + EC > 400 μg/m

EC × 1.3 > 400 μg/m

Yes

Total

693 (79.3%)

11 (1.3%)

704 (80.5%)

Yes

44 (5.0%)

126 (14.4%)

170 (19.5%)

Total

737 (84.3%)

137 (15.7%)

874 (100.0%)

Table V-6 lists the 19 occupations found to have at least one sample in which the level of TC was over the interim 400

μg/m

concentration limit (TC = EC × 1.3). Table V-6 is sorted by the median TC result. The table also lists the minimum value, median value, and the total number of valid samples for these occupations. TC values varied widely among all miners' occupations.

Table V-6.—Occupations With at Least One Sample Greater Than or Equal to 400

μg/m

Occupation

Total samples

Minimum

Median

Maximum

Engineer

438

Roof Bolter, Mounted

335

588

Miner, Stope

165

330

622

Clean Up Man

283

499

Mucking Machine Operator

278

872

Shuttle Car, Diesel

257

419

Drill Operator, Rotary Air

231

1145

Belt Crew

225

502

Blaster, Powder Gang

101

216

960

Drill Operator, Jumbo

194

708

Complete Load-Haul-Dump

188

824

Miner, Drift

185

1459

Scaling (Hand)

166

2014

Roof Bolter, Rock

157

829

Truck Driver

184

155

1074

Front End Loader

155

136

1743

Drill Operator, Rotary

133

1109

Scaling (Mechanical)

131

750

Utility Man

638

Supervisor

856

Crusher Operator

427

Table V-7 and Chart V-1 provide the frequencies and percent of overexposures among the four commodities. Chart V-2 provides the frequency of overexposures among the commodities. The metal mines have the

highest percent of overexposures followed by stone than other N/M mines. All 15 samples collected in trona mines were less than 200

μg/m

. For all samples combined, 15.7% were above 400

μg/m

Table V-7.—Baseline Samples by Commodity (TC=EC × 1.3)

Commodity

Number

<400

μg/m

Number

>400

μg/m

Total

Percent

>400 μg/m

Metal

148

189

21.7

Stone

435

519

16.2

Other N/M

139

151

7.9

Trona

0.0

All Mines

737

137

874

15.7

BILLING CODE 4510-43-P

EP14AU03.001

Chart V-3 shows the number of mines with a specific number of overexposures. Examination of the frequency of mines with one or more overexposures shows that 51 (29.8%) mines are in this category.

EP14AU03.002

At 14 of the mines, all the samples were above 400

μg/m

. Between one and five samples were taken at each of these mines. No overexposures were found in 120 (70%) of the mines sampled. (

See

Chart V-4.)

EP14AU03.003

BILLING CODE 4510-43-C

Tables V-8 and V-9 summarize sample statistics by commodity for total carbon calculated by TC = EC × 1.3 and TC = EC + OC respectively. Overall, the mean TC as calculated by EC × 1.3 is 222 μg/m

. The median level is 153 μg/m

. The mean TC level by OC + EC is 263 μg/m

and the median level is 209 μg/m

. Individual exposure levels of TC vary widely within all commodities and most mines. The statistics reported in Tables V-8 and V-9 were chosen to be consistent with those reported in the 31-Mine Study and the Exposure Assessment.

The mean TC values (EC × 1.3) are somewhat lower than the interim compliance limit of 400 μg/m

. The mean (median) TC value for metal mines is 296(239) μg/m

. The mean for stone is 214(136), other N/M is 170(129) and for trona mines is 90(91) μg/m

. Table V-8 lists additional statistics for EC values compiled by commodity.

Table V-8.—Average Levels of Total Carbon by Commodity Measured in

μg/m

(EC × 1.3)

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

)]

EC × 1.3

Metal

Stone

Other N/M

Trona

All mines

Number of Samples

189

519

151

874

Maximum

2,014

1,743

824

194

2,014

Median

239

136

129

153

Mean

296

214

170

222

Std. Error

95% CI Upper

333

233

191

119

236

95% CI Lower

258

195

148

207

The mean TC values as calculated by OC + EC are also somewhat lower than the interim compliance limit of 400 μg/m

. The mean (median) TC value for metal mines is 323(285) μg/m

. The mean for stone is 263(200), other N/M is 202(168) and for trona mines is 128(126) μg/m

. Table V-9 lists additional statistics for TC values compiled by commodity.

Table V-9.—Average Levels of Total Carbon by Commodity Measured in

μg/m

(OC + EC)

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

)]

OC + EC

Metal

Stone

Other N/M

Trona

All mines

Number of Samples

189

519

151

874

Maximum

1,742

1,559

740

218

1,742

Median

285

200

168

126

209

Mean

323

263

202

128

263

Std. Error

95% CI Upper

356

284

223

154

278

95% CI Lower

289

243

181

102

248

Tables V-10 and V-11 show total DPM exposures for the baseline and the 31-Mine Study. For baseline sampling DPM was calculated by EC × 1.3 × 1.25. The 1.25 factor represents the assumption that TC comprises 80 percent of DPM. Section VI-B-3 discusses the relationship between elemental and total carbon. The mean (median) value is 369(299) μg/m

for metal mines, 267(170) for stone mines, 212(162) for other NM, and 113(113) μg/m

for trona mines. The total DPM exposures for table V-11 were calculated as (OC + EC) × 1.25. The mean values from the baseline samples appear to be lower than the mean values obtained during the 31-Mine Study.

Table V-10.—Baseline DPM Concentrations (EC × 1.3 × 1.25,

μg/m

by Mine Category

Metal

Stone

Other N/M

Trona

All mines

Number of Samples

189

519

151

874

Maximum

2518

2178

1030

242

2518

Median

299

170

162

113

191

Mean

369

267

212

113

277

Std. Error

95% UCL

416

291

239

149

296

95% LCL

323

243

185

259

Table V-11.—Baseline DPM Concentrations ((EC + OC) × 1.25,

μg/m

by Mine Category

Metal

Stone

Other N/M

Trona

All mines

Number of Samples

189

519

151

874

Maximum

2177

1949

925

273

2177

Median

357

250

211

158

261

Mean

403

329

252

160

329

Std. Error

95% CI Upper

445

355

279

193

348

95% CI Lower

361

303

226

127

310

Table V-12.—31-Mine Study DPM Concentrations (

μg/m

by Mine Category

Metal

Stone

Other N/M

Trona

Number of Samples

116

105

Maximum

2581

1845

1210

331

Median

491

331

341

Mean

610

466

359

Std. Error

95% CI Upper

699

537

412

113

95% CI Lower

522

394

306

Chart V-5 compares the means from Tables V-10, V-11 and V-12. The mines selected in the 31-Mine Study (Table V-12) were not randomly selected and is therefore not considered representative of the underground M/NM mining industry. Additionally the industry has continued to change the diesel-powered fleet to low emission engines that reduce diesel particulate matter exposure. Workers inside equipment cabs were not sampled during the 31-Mine Study due to possible interference from cigarette smoke. Personal samples taken inside cabs were not avoided during baseline compliance assistance sampling.

EP14AU03.004

B. DPM Control Technology

In addition to conducting baseline DPM sampling at underground metal and nonmetal mines, MSHA participated in a number of compliance assistance activities directed at improving sampling and assisting mine operators with selection and implementation of appropriate DPM control technology. Some of these activities were directed to a segment of, or the entire mining industry. Others were conducted on a mine specific basis. In general, those activities directed toward a large number of mines included outreach programs, workshops, Web site postings and publications. Those activities directed at an individual mine included evaluation of a specific control technology, a review of the technology in use, or that would be available at a specific mine.

Regional DPM Seminars.

During September and October 2002, MSHA conducted regional DPM seminars at Ebensburg, PA, Knoxville, TN, Lexington, KY, Des Moines, IA, Kansas City, MO, Albuquerque, NM, Coeur d'Alene, ID, Green River, WY, and Elko, NV. These full-day seminars were offered free of charge in the major underground metal and nonmetal mining regions of the country to facilitate attendance by key mining industry personnel. The seminars covered the health effects of DPM exposure, the history and specific provisions of the regulation, DPM controls, DPM sampling, and the DPM Estimator, which is an interactive computer spreadsheet program used for analyzing a mine's DPM sources and controls.

NIOSH Diesel Emission Workshops.

MSHA staff participated in two NIOSH Diesel Emissions and Control Technologies in Underground Metal and Nonmetal Mines in February and March 2003 in Cincinnati, OH and Salt Lake City, UT. These workshops provided technical presentations and a forum for discussing issues relating to control technologies for reducing miners' exposure to particulate matter and gaseous emissions from the exhaust of diesel-powered vehicles in underground mines, and to help mine managers, maintenance personnel, safety and health professionals, and ventilation engineers select and apply diesel particulate filters and other control technologies in their mines. Speakers represented MSHA, NIOSH, and several mining companies, and ample time was provided for questions and in-depth technical discussion of issues raised by attendees.

NSSGA DPM Sampling Workshop:

As part of the Kentucky Stone Association Seminar, MSHA staff conducted a diesel particulate sampling workshop in Louisville, Kentucky from December 11 through 13, 2002. The three day seminar was hosted by the National Stone Sand and Gravel Association. On the first day of the seminar, diesel particulate sampling procedures were reviewed. The participants were trained in pump calibration, sample train assembly and note taking. On the second, participants traveled to the Rogers Group Jefferson County Mine and conducted full shift sampling on underground workers. MSHA technical support staff took ventilation measurements and collected area samples to assess mine DPM emissions. On the final day of the seminar, engine emission and ventilation measurements were reviewed with the participants. Additionally, the MSHA DPM outreach material was reviewed and discussed. Approximately 10 industry participants attended the seminar.

Nevada Mining Association Safety Committee.

MSHA staff attended a meeting of the Nevada Mining Association Safety Committee in Elko, NV in April 2003 to discuss DPM control technologies. Discussion topics included bio-diesel fuel blends, various fuel additives and fuel pre-treatment devices, to mine ventilation, environmental cabs, clean engines, and diesel particulate filter systems. The mining companies' experiences with and perspectives on these technologies were discussed, along with MSHA's experiences, observations made at various mines, and results of laboratory and field testing.

MSHA South Central Joint Mine Safety and Health Conference.

A DPM workshop was presented at this conference in April 2003 in New Orleans, LA. This workshop included a detailed history and explanation of the provisions of the MNM DPM regulation, and a technical presentation on feasible DPM engineering controls.

2003 Joint National Meeting of the Joseph A. Holmes Safety Association, National Association of State Mine Inspection and Training Agencies, Mine Safety Institute of America, and Western TRAM (Training Resources Applied to Mining).

A DPM workshop was presented at this joint conference in June 2003 in Reno, NV. This workshop included a detailed history and explanation of the provisions of the MNM DPM regulation, and a technical presentation on DPM sampling, analytical tools for identifying and evaluating DPM sources in mines, and feasible DPM engineering controls.

Web site postings.

MSHA created a single source page for DPM final rules for Metal/Nonmetal Mines on its Web site,

www.msha.gov

. Links were established to obtain information on specific topics, including:

—DRAFT Metal and Nonmetal Health Inspection Procedures Handbook, Chapter T—Diesel Particulate Matter Sampling

—DRAFT Diesel Particulate Matter Sampling Field Notes

—Metal and Nonmetal Diesel Particulate Matter (DPM) Standard Error Factor for TC Analysis Written Compliance Strategy

—Metal and Nonmetal Diesel Particulate Matter (DPM) Standard Draft Compliance Guide

—Other Resources

—NIOSH Listserve

—Diesel Emissions and Control Technologies in Underground Metal and Nonmetal Mines

—Metal and Nonmetal Diesel Particulate Filter Selection Guide

—Baseline DPM Sample Results

—PowerPoint Presentations

—From Compliance Assistance Workshops on Diesel Rule

—Summary of Requirements Mine Safety and Health Administration's (MSHA's) Standard on Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners that are in effect as of July 20, 2002.

—SKC Diesel Particulate Matter Cassette with Precision-jeweled Impactor

—Diesel Particulate Matter (DPM) Control Technologies with Percent Removal Efficiency

—Diesel Particulate Matter (DPM) Control Technologies

—Table I: Non-Catalyzed Particulate Filters, Base Metal Particulate Filters, and Paper Filters

—Table II: Catalyzed (Platinum Based) Diesel Particulate Filters

—Work Place Emissions Control Estimator

—Advanced Notice of Proposed Rule Making (ANPRM)

—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners (ANPRM)—09/25/2002

—Final Rules

—Part II—30 CFR Part 57—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners—01/19/2001

—Part II—30 CFR Part 57—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners—Delay of Effective Dates—05/21/2001

—Part II—30 CFR Part 57—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners—Final Rule and Proposed Rule—07/05/2001

—Part II—30 CFR Part 57—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners; Final Rule—02/27/2002

—Part II—30 CFR Part 57—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners; Final Rule—07/18/2002

—Regulatory Economic Analysis

—Final Regulatory Economic Analysis And Regulatory Flexibility Analysis for Final Rule on 30 CFR Parts 57 Final Standards and Regulations—Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners

—News Releases

—MSHA Rules Will Control Miners' Exposure to Diesel Particulate—01/18/2001

—Program Information Bulletins

—PIB01-10 Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners—08/28/2001

—PIB02-04 Potential Health Hazard Caused by Platinum-Based Catalyzed Diesel Particulate Matter Exhaust Filters—05/31/2002—

—PIB02-08 Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners-Summary of Settlement Agreement—08/12/2002

In addition to the Web site postings specifically intended for the metal and nonmetal mining industry, MSHA has created a Diesel Single Source Page for the coal industry. A list of approved engines is accessible from the coal page. Many of the other topics found on that page may also be of interest to the metal and nonmetal mining industry, particularly for those operations at gassy metal/nonmetal mines where permissible equipment is required.

Publications:

As part of the settlement agreement, MSHA agreed to issue citations for violations of the interim concentration limit only after MSHA and NIOSH are satisfied with the performance characteristics of the SKC sampler. During the 31-Mine study, MSHA observed that the deposit area of the SKC submicron impactor filter was not as consistent as those obtained for preliminary evaluation. This was attributed to inconsistent crimping of the aluminum foil cone on the filter capsule.

NIOSH, in collaboration with MSHA and SKC undertook a project to redesign the filter capsule and improve the consistency of the deposit area. This was accomplished by replacing the cone with a 32-mm inside diameter ring and replacing the 37-mm filter with a 38-mm filter. These modifications provided a

consistent 8.04 square centimeter deposit and eliminated leakage around the filter. The results of this project were prepared into a scientific publication “Sampling Results of the Improved SKC Diesel Particulate Matter Cassette” by James D. Noll, Robert J. Timko, Linda McWilliams, Peter Hall, and Robert A. Haney. This paper is being peer reviewed for publication in a scientific journal. The following abstract was prepared for the study results:

Diesel particulate matter (DPM) cassettes, manufactured by SKC, Inc., Eighty Four, PA, are designed to collect airborne particulates being emitted by diesel powered machinery. These devices, primarily used in underground metal/non-metal mines, enable officials to determine miner exposure to DPM. The SKC DPM cassette is a size selective sampler that was designed by researchers with the U.S. Bureau of Mines, now a part of the National Institute for Occupational Safety and Health (NIOSH), and SKC engineers to collect DPM. This cassette is preferred to a conventional respirable dust sampler because, if DPM is sampled in the presence of carbonaceous ore dust, the ore dust and DPM will collect on the quartz filter, causing the carbon attributed to DPM to be artificially high. In this study, NIOSH researchers investigated the ability of the SKC DPM cassette to collect DPM while preventing mineral dust from collecting on the filter. This cassette discriminated dusts and efficiently collected DPM in both laboratory and field evaluations. In the presence of carbon-based mineral dust having an average concentration of 8 mg/m

, no mineral dust was found on SKC DPM cassette filters. NIOSH researchers did discover that DPM deposits on filters that were manufactured prior to August 2002 were non-uniform and inconsistent across the filter surfaces. DPM deposit cross-sectional areas varied from 6 to 9 cm

. To correct this problem, SKC modified the cassette. The resulting cassette produced areas of DPM deposit between 8.11 and 8.21 cm

, a difference of less than 2%.

Specific control technology studies.

Following the settlement agreement, MSHA was invited by various mining companies to evaluate the effectiveness of several different control technologies for diesel particulate matter. These control technologies included ceramic filters, bio-diesel fuel and a fuel oxygenator. Company participation was essential to the success of each study. Ceramic filters were evaluated in two mines, one where MSHA was the only investigator and one where NIOSH was the primary investigator. In the MSHA study, DPM on a production unit was evaluated with and without ceramic filters installed on the loader and trucks. In the NIOSH study a variety of ceramic filters were tested in an isolated zone.

Bio-diesel fuel was evaluated in two mines. In one mine, a 20 and 50 percent recycled bio-diesel fuel and a 50 percent new bio-diesel were evaluated. In the second mine, a 35 percent recycled bio-diesel fuel and a 35 percent new bio-diesel fuel were evaluated.

The fuel oxygenator system was evaluated in one mine. The mine exhaust was sampled with and without the units installed. For the tests with the oxygenator units, the oxygenator units were installed on all production equipment.

Following is a summary of the five individual mine technology evaluation studies:

Kennecott Greens Creek Mining Company:

The Mine Safety and Health Administration and Kennecott Greens Creek Mining Company participated in a collaborative study to verify the efficiency of catalyzed ceramic diesel particulate filters for reducing diesel emissions. The goal of the study was the identification of site-specific, practical mine-worthy filter technology.

This series of tests was designed to determine the reduction in emissions and personal exposure that can be achieved when ceramic filters are installed on a loader and associated haulage trucks operating in a production stope. Relative engine gaseous and diesel particulate matter emissions were also determined for the equipment under specific load condition.

The tests were conducted over a two-week period. Three shifts were sampled with ceramic after-filters installed; and three shifts were sampled without the after-filters installed. Personal samples were collected to assess worker exposures. Area samples were collected to assess engine emissions. Both gaseous and diesel particulate measurements were taken.

Sampling results indicate significant reductions in both personal exposures and engine emissions. These results also indicated that factors such as diesel particulate contamination of intake air, stope ventilation parameters, and isolated atmospheres in vehicle cabs as well as the ceramic diesel particulate filters may have a significant impact on personal exposures. The following findings and conclusions were obtained from the study:

1. The results of the raw exhaust gas measurements conducted during the study indicated that the engines were operating properly.

2. The ceramic filters installed on the machines used in this study did not adversely affect the machine operation. Even with some apparent visual cracking from the rotation of the filter media, the ceramic filters removed more than 90% of the DPM. The filters passively regenerated during machine operation.

3. The Bosch smoke test provides an indication of filter deterioration; however, the colorization method does not quantify the results.

4. Personal DPM exposures were reduced by 60 to 68 percent when after-filters were used.

5. CO levels decreased by up to one-half when the catalyzed filters were being used. There appeared to be an increase in NO

when catalyzed filters are being used; however, it was unclear whether this increase was due to data variability, changes in ventilation rate, or the use of the catalyzed filters.

6. The use of cabs reduced DPM concentrations by 75 percent when after-filters were used and by 80 percent when after-filters were not in use.

7. Ventilation airflow was provided to the stopes through fans with rigid and bag tubing. Airflow was the same or greater than the Particulate Index, but typically lower than the gaseous ventilation rate.

8. The use of ceramic after-filters reduced average engine DPM emissions by 96 percent.

9. The reduction in personal exposure was not attributed solely to after-filter performance because other factors such as ventilation, upwind equipment use, and cabs also influence personal exposure.

Carmeuse North America, Inc., Maysville Mine:

MSHA entered into a collaborative effort with NIOSH, Industry, and the Kentucky Department of Energy to test DPM emissions and exposures when using various blends of bio-diesel fuels in an underground stone mine. As part of its compliance assistance program, MSHA provides support to mining operations to evaluate diesel particulate control technologies. The study was initiated by the industry partner, with MSHA and NIOSH providing support for study design, data collection, and sample and data analysis. Project funding was provided by Carmeuse and Kentucky Department of Energy, through the Kentucky Clean Fuels Coalition.

The initial study was conducted in two phases, a 20% bio-diesel and a 50% bio-diesel blend of recycled vegetable oil, each mixed with 100% low sulfur No. 2 standard diesel fuel. Baseline conditions were established using low sulfur No. 2 standard diesel fuel. In a third phase of the study, a 50% blend of new soy bio-diesel fuel was tested.

Area samples were collected at shafts to assess equipment emissions. Personal samples were collected to assess worker exposure. These samples were analyzed by NIOSH using the NIOSH 5040

method to determine total carbon and elemental carbon concentrations. Results indicate that significant reductions in emissions and worker exposure were obtained for all bio-diesel mixtures. These reductions were in terms of both elemental and total carbon. Preliminary results for the 20% and 50% recycled vegetable oil indicated 30 and 50 percent reductions in DPM emissions and exposures, respectively. Preliminary results for the tests on the 50% blend of new soy bio-diesel fuel, showed about a 30 percent reduction in DPM emissions and exposures.

Carmeuse North America, Inc., Black River Mine:

Following the success of the bio-diesel tests at Maysville Mine, Carmeuse requested assistance in continuing the bio-diesel optimization testing at their Black River Mine. In this test two bio-diesel blends along with a baseline test were made. For each test personal exposures and the mine exhaust were tested for two shifts. The two bio-diesel blends included a 35% recycled vegetable oil and a 35% blend of new soy oil. Preliminary results for both the 35% recycled vegetable oil and the 35% blend of new soy bio-diesel fuel showed about a 30 percent reduction in DPM emissions and exposures.

Rogers Group, Jefferson County Mine:

MSHA personnel were invited by the Company to evaluate a fuel oxygenation system. The oxygenator is installed in the fuel line of the diesel equipment. The company was installing the units to increase fuel economy and was interested in determining their effect on DPM. MSHA conducted baseline sampling prior to the installation of the units. Personal samples were collected on production workers and area samples were collected in the mine exhaust airflow. The units were installed on loaders and trucks. The sampling was repeated after the units had accumulated 100 hours of operation. Preliminary results indicated that the use of the fuel oxygenator had no measurable effect on either DPM exposure or emissions.

Review of the Technology in Use Assistance

Martin Marietta Aggregates, North Indianapolis Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in March 2003. The mine's DPM sampling history was reviewed, along with current operating and equipment maintenance practices, mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. Currently, mechanical ventilation is used at the mine and an upgrade to the ventilation system was in progress. The full range of DPM engineering controls was discussed, an exhaust temperature measurement and data logging system was demonstrated, and easy-to-use computer software for using such data to select appropriate DPM filter systems was presented. A simple approach for measuring the effectiveness of cab air filtering and pressurization systems was demonstrated, MSHA's computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls was presented, the highest DPM-emitting equipment was identified (so that future equipment-specific DPM control efforts could be appropriately focused), and the likely effect of various ventilation system upgrades was discussed.

Martin Marietta Aggregates, Parkville Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in April 2003. The mine's DPM sampling history was reviewed, along with current operating and equipment maintenance practices, mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. Mechanical ventilation is currently used at the mine and an upgrade to the ventilation system was in progress. The full range of DPM engineering controls was discussed, an exhaust temperature measurement and data logging system was demonstrated, and easy-to-use computer software for using such data to select appropriate DPM filter systems was presented. A simple approach for measuring the effectiveness of cab air filtering and pressurization systems was demonstrated, computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls was presented, the highest DPM-emitting equipment were identified (so that future equipment-specific DPM control efforts could be appropriately focused), and the likely effect of various ventilation system upgrades was discussed.

Martin Marietta Aggregates, Kaskaskia Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in May 2003. The mine's DPM sampling history was reviewed, along with current operating and equipment maintenance practices, mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. Currently, natural ventilation is used at the mine. The full range of DPM engineering controls was discussed, an exhaust temperature measurement and data logging system was demonstrated, and easy-to-use computer software for using such data to select appropriate DPM filter systems was presented. A simple approach for measuring the effectiveness of cab air filtering and pressurization systems was demonstrated, computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls was presented, the highest DPM-emitting equipment were identified (so that future equipment-specific DPM control efforts could be appropriately focused), and the likely effect of various ventilation system upgrades was discussed.

Martin Marietta Aggregates, Manheim Mine:

Rogers Group, Oldham County Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in November 2002. Extensive DPM sampling was conducted at this mine. Both personal exposure samples and area samples were collected. None of the personal samples exceeded 160 μg/m

. Current operating and equipment maintenance practices were reviewed, along with mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. Mechanical ventilation was provided for the mine. The full range of DPM engineering controls was discussed. DPM samples were collected inside and outside equipment cabs. Results from this survey indicate the environmental cabs provided significant reduction in

the DPM exposure of the equipment operators.

Rogers Group, Jefferson County Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in December 2002. Both personal exposure samples and area samples were collected. The highest personal sample, collected on the loader, was 468 μg/m

. The loader was operated with the window open. Current operating and equipment maintenance practices were reviewed, along with mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. Mechanical ventilation was provided for the mine. The full range of DPM engineering controls was discussed. The Estimator, MSHA's computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls, was presented, the highest DPM-emitting equipment were identified so that future equipment-specific DPM control efforts could be appropriately focused. Finally, the likely effect of various ventilation system upgrades was discussed.

Nalley and Gibson, Georgetown Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in May 2003. The mine's DPM sampling history was reviewed, along with current operating and equipment maintenance practices, mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. DPM samples were collected to assess improvements since the baseline sampling. Currently, mechanical ventilation provides airflow to the mine. The full range of DPM engineering controls was discussed, an exhaust temperature measurement and data logging system was demonstrated. An easy-to-use computer software for using such data to select appropriate DPM filter systems was presented. A simple approach for measuring the effectiveness of cab air filtering and pressurization systems was demonstrated. The Estimator, MSHA's computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls, was presented. The highest DPM-emitting equipment were identified so that future equipment-specific DPM control efforts could be appropriately focused, and the likely effect of various ventilation system upgrades was discussed.

Stone Creek Brick Company:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in May 2003. DPM samples were collected on underground workers. The mine's DPM sampling history was reviewed, along with current operating and equipment maintenance practices, mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. The mine uses mechanical ventilation to provide airflow to the mine. The full range of DPM engineering controls was discussed. None of the equipment were equipped with environmental cabs. The Estimator, MSHA's computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls, was presented. The highest DPM-emitting equipment were identified so that future equipment-specific DPM control efforts could be appropriately focused. Also, the likely effect of various ventilation system upgrades was discussed.

Wisconsin Industrial Sand Co., Maiden Rock Mine:

Gouverneur Talc Company, Inc., No. 4 Mine:

MSHA personnel provided DPM compliance assistance at this mine during a full-day visit in May 2003. DPM samples were collected on underground workers. The mine's DPM sampling history was reviewed, along with current operating and equipment maintenance practices, mine ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. The full range of DPM engineering controls was discussed, an exhaust temperature measurement and data logging system was demonstrated, and easy-to-use computer software for using such data to select appropriate DPM filter systems was presented. A simple approach for measuring the effectiveness of cab air filtering and pressurization systems was demonstrated, a computer spreadsheet software for evaluating the individual and combined effect of DPM emission sources and controls was presented, the highest DPM-emitting equipment was identified (so that future equipment-specific DPM control efforts could be appropriately focused), and the likely effect of various ventilation system upgrades was discussed.

Laboratory Compliance Assistance conducted by MSHA:

In addition to the compliance assistance field tests, MSHA's diesel testing laboratory has been working with manufacturers to evaluate various types of DPM control technologies. Certain of these technologies can be applied in either underground metal/nonmetal or coal mines.

Evaluating paper/synthetic media as exhaust filters:

MSHA has been evaluating paper/synthetic media as exhaust filters. These filters have shown high DPM removal efficiencies in excess of 90% in the laboratory when tested on MSHA's test engine using the test specified in subpart E of 30 CFR part 7. The laboratory has tested approximately 20 different paper/synthetic media from 10 different filter manufacturers. Even though much of this work is directed to underground coal mine applications for use on permissible equipment, this technology is available for use on permissible equipment that is used in underground gassy metal/nonmetal mines. In addition, some underground coal mine operators have considered adding exhaust heat exchanger systems to nonpermissible equipment in order to use the paper/synthetic filters in place of ceramic filters (a heat exchanger is needed to reduce the exhaust gas temperature to below 302 °F for these types of filters). This could also be an option for metal/nonmetal equipment that would need DPM filter technology, particularly in operations in gassy mines where permissible equipment is required.

Evaluating Ceramic Filter Systems:

MSHA has worked with six different ceramic filter system manufacturers to evaluate the effects of their catalytic washcoats on NO

production. As discussed elsewhere in this preamble, catalytic washcoats on the ceramic filters may cause increases in NO

levels. MSHA used its test engine and followed the test procedures in subpart E of 30 CFR part 7. MSHA has posted on its Web site on the Diesel Single Source Page a list of ceramic filters that have significantly increased NO

levels. MSHA has also listed the ceramic filters that are not known to have increased NO

levels. MSHA also checked the DPM removal efficiencies for these filters during the laboratory tests and the efficiency results have agreed with the efficiencies posted on the Diesel Single Source Page of 85% for cordierite and 87% for silicon carbide. MSHA also worked with NIOSH during these tests

to collect DPM samples for EC analysis using the NIOSH 5040 method. The laboratory results showed that the filters removed EC with efficiencies up to 99%.

Evaluation of Fuel Oxygenator System:

MSHA recently completed laboratory tests on a Rentar in-line fuel catalyst. The Rentar unit was installed on a Caterpillar 3306ATAAC which was coupled to a generator. An electrical load bank was used to load the engine under various operating conditions. The engine was baselined for gaseous and DPM emissions without the Rentar; then, the Rentar was installed and operated for 100 hours of break-in. The gaseous and DPM emission measurements were repeated after the 100 hour break-in. The preliminary laboratory results showed some measurable reductions in whole DPM. Samples were also collected for EC analysis using the NIOSH 5040 method. Those results are currently being evaluated by NIOSH.

Evaluation of a Magnet System:

MSHA is preparing to perform laboratory tests for Ecomax, a manufacturer of a magnet system installed on the fuel line, oil filter, air intake and radiator. A preliminary MSHA field test of this product was done at a surface aggregate operation. The magnetic device demonstrated a 30% reduction in CO levels. Subsequent laboratory testing will include DPM measurements.

Additional Testing:

MSHA is also planning a lab test on a manufacturer's fluidized bed, several types of fuel additives, and a fuel preparative. The test plans and the required test hardware are currently being discussed with the respective manufactures of these products.

VI. Exposure Assessment and Literature Update

A. Introduction

Section VI.B summarizes new exposure data that have become available since publication, on January 19, 2001, of the existing rule limiting DPM levels in underground metal and nonmetal mines. Next, in Section VI.C, we survey the most recent scientific literature (April 2000-March 2003) pertaining to adverse health effects of DPM and fine particulates in general.

B. DPM Exposures in Underground Metal and Nonmetal Mines

In the existing risk assessment (66 FR 5752) we evaluated exposures based on 355 samples collected at 27 underground U.S. M/NM mines prior to the rule's promulgation. 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 existing risk assessment were collected prior to 1999, and some were collected as long ago as 1989.

Two new bodies of DPM exposure data, collected subsequent to promulgation of the 2001 rule, have now been compiled for underground M/NM mines: (1) Data collected in 2001 from 31 mines for purposes of the 31-Mine Study (Ref. 31-Mine Study) and (2) data collected between 10/30/2002 and 3/26/2003 from 171 mines to establish a baseline for future samples (Ref. Baseline Samples, 2003). Both of these datasets have been placed into the public record, and they are summarized in the next two subsections below. Following these summaries, we discuss the relationship between EC and TC, including the ratio of EC to TC (EC:TC). This discussion will be based entirely on samples taken for the 31-Mine Study, since those samples were controlled for potential TC interferences from tobacco smoking and oil mist, whereas the baseline samples were not.

1. Data from Joint Study

As described in greater detail in MSHA's final report on the 31-Mine Study, MSHA collected 464 DPM samples in 2001 at 31 underground M/NM mines. Of these 464 samples, 106 were voided, most of them due to potential interferences resulting in invalid TC content used to evaluate DPM exposures. Table VI-1 shows how the remaining 358 valid DPM samples were distributed across four broad mine categories. All samples at one of the metal mines were voided, leaving 30 mines with valid samples indicating DPM concentrations.

Table VI-1.—Number of DPM Samples, by Mine Category

Number of mines with valid samples

Number of valid samples

Average Number of valid samples per mine

Metal

116

10.5

Stone

105

11.7

Trona

18.0

Other

11.9

Total

358

12.5

Table VI-2 summarizes the valid DPM concentrations observed in each mine category, assuming that submicrometer TC, as measured by the SKC sampler, comprises 80 percent of all DPM. The mean concentration across all 358 valid samples was 432 μg/m

(Std. error = 21.0 μg/m

). The mean concentration was greatest at metal mines, followed by stone and “other N/M.” At the three trona mines sampled, both the mean and median DPM concentration were substantially lower than what was observed for the other categories. This was due to the increased ventilation used at these mines to control methane emissions.

Table VI-2.—DPM Concentrations (μg/m

By Mine Category.

DPM Is Estimated by TC/0.8

Metal

Stone

Trona

Other N/M

Number of samples

116

105

Minimum

46.

16.

20.

27.

Maximum

2581.

1845.

331.

1210.

Median

491.

331.

82.

341.

Mean

610.

465.

94.

359.

Std. Error

44.7

36.0

9.4

26.6

95% UCL

699.

537.

113.

412.

95% LCL

522.0

394.

75.

306.

After adjusting for differences in sample types and in occupations sampled, DPM concentrations at the non-trona mines were estimated to be about four to five times the concentrations found at the trona mines. Although there were significant differences between individual mines, the adjusted differences between the general categories of metal, stone, and other N/M mines were not statistically significant.

For the 304 valid samples taken at mines other than trona, the mean DPM concentration was 492 μg/m

(Std. error = 23.0).

These conclusions derive from an analysis of variance, based on TC measurements, as described in the report of the 31-Mine Study. They depend on an assumption that the ratio of DPM to TC is uncorrelated with mine category, sample type (

i.e.

, personal or area), and occupation.

Again assuming that submicrometer TC as measured by the SKC sampler comprises 80 percent of DPM, the mean DPM concentration observed was 1019 μg/m

at the single mine exhibiting greatest DPM levels. Four of the nine valid samples at this mine exceeded 1487 μg/m

. In contrast, DPM concentrations never exceeded 500 μg/m

at 8 of the 30 mines with valid samples (2 of the 11 metal mines, 1 of the 3 stone, all 3 trona, and 2 of the 7 other N/M). (Note that 500 μg/m

is the whole particulate equivalent of the 400 μg/m

interim standard.) Some individual measurements exceeded 200DPM μg/m

at all but one of the mines sampled.

2. Baseline Data

An analysis of MSHA's baseline sampling appears in Section V, Compliance Assistance, and is used as the basis for this dicussion.

Table VI-1 summarizes, by general commodity, the EC levels measured during this sampling. The overall mean eight-hour full shift equivalent EC concentration of samples in this study was 170 μg/m

, and the overall median was 117 μg/m

. Table VI-2 provides a similar summary for estimated DPM levels, using TC/0.8 and TC ≉ 1.3 × EC.

Under these assumptions, the estimated mean DPM level was 277 μg/m

, and the median was 191 μg/m

. Since the baseline data and the 31-Mine study both showed significantly lower levels at trona mines than at other underground M/NM mines, Tables VI-7 and VI-8 present overall results both including and excluding the three underground trona mines sampled.

The relationship DPM ≉ TC/0.8 is the same as that assumed in the existing risk assessment. The relationship TC ≉ 1.3 × EC was formulated under the settlement agreement, based on TC:EC ratios observed in the joint 31-Mine Study, as described in the next subsection of this exposure assessment.

Table VI-1.—Baseline EC Concentrations

8-hour full shift equivalent EC concentration—(μg/m

)

Metal

Stone

Other N/M

Trona

Total

Total excluding Trona

Number of samples

189

519

151

874

859

Maximum

1549

1340

634

149

1549

Median

184

104

117

120

Mean

227

164

130

170

172

Std. Error

14.6

7.5

8.5

10.3

5.8

5.9

95% UCL

256

179

147

182

184

95% LCL

198

150

115

159

161

Table VI-2.—Baseline DPM Concentrations

Estimated 8-hour full shift equivalent DPM concentration—(μg/m

)

Metal

Stone

Other N/M

Trona

Total

Total excluding Trona

Number of samples

189

519

151

874

859

Maximum

2518.

2178.

1030.

242.

2518.

Median

299.

170.

162.

113.

191.

195.

Mean

369.

267.

212.

113.

277.

280.

Std. Error

23.8

12.2

13.8

16.7

9.4

9.5

95% UCL

416.

291.

239.

149.

295.

299.

95% LCL

323.

243.

185.

77.

259.

261.

Baseline EC sample results varied widely between mines within commodities and also within most mines. Table VI-3 summarizes baseline EC results for the 19 occupations found to have at least one sample where the

EC level exceeded the proposed 308 μg/m

8-hour full shift equivalent interim EC limit. As indicated by the table, EC levels varied widely within each occupation.

Table VI-3.—Baseline EC Concentrations for Occupations With at Least One Value Exceeding Proposed Interim EC Limit

Occupation

8-hour full shift equivalent EC concentration (μg/m

)

Number of valid samples

Minimum

Median

Maximum

Scaling (hand)

128

1,549

Front-end Loader

155

104

1,340

Miscoded

395

450

1,123

Drill Operator

122

880

Truck Driver

183

118

826

Blaster, Power Gang

100

165

738

Miner, Drift

134

712

Mucking Machine

213

671

Supervisor

658

Roof Bolter

167

638

Complete Loader

145

634

Scaling (mechanical)

101

577

Utility Man

491

Miner, Stope

127

254

479

Belt Crew

173

386

Cleanup Man

217

384

Engineer

337

Crusher operator

328

Shuttle car operator

323

Figure VI-1 depicts, by mine category, the percentage of baseline samples that exceed the proposed interim limit of 308 μg/m

. Underground metal mines exhibited the highest proportion of samples exceeding this limit, followed by stone and then other nonmetal mines. All 15 samples collected in the three trona mines met the proposed limit. Across all commodities, 15.7 percent of the 874 valid baseline samples exceeded the interim EC limit.

EP14AU03.005

Figure VI-2 shows how samples exceeding the proposed interim EC limit were distributed over individual mines. One to five baseline samples were taken at each mine. In 120 of the 171 mines sampled (70 percent), none of the

baseline EC measurements exceeded 308 μg/m

. The remaining 51 mines (30 percent) had at least one sample for which EC exceeded 308 μg/m

. All samples taken at 14 of the mines exceeded the proposed interim limit.

EP14AU03.006

3. Relationship Between Elemental and Total Carbon

Unlike the 31-Mine Study, no special precautions were taken during MSHA's baseline sampling to avoid tobacco smoke or other substances that could potentially interfere with using TC (

i.e.

, EC + OC) as a surrogate measure of DPM. Therefore, the baseline data should not be used to evaluate the OC content of DPM or the ratio of EC to TC within DPM. In the 31-Mine Study, great care was taken to void all samples that may have been exposed to tobacco smoke or other extraneous sources of organic carbon. Accordingly, the analysis of the EC:TC ratio we present here relies entirely on data from the 31-Mine Study. It is important to note that most of the samples in this study were taken in the absence of exhaust filters to control DPM emissions. Since exhaust filters may have different effects on EC and OC emissions, the results described here apply only to mine areas where exhaust filters are not employed.

Figure VI-3 plots the EC:TC ratios observed in the 31-Mine Study against the corresponding TC concentrations. The various symbols shown in the plot identify samples taken at the same mine. The EC:TC ratio ranged from 23 percent to 100 percent, with a mean of 75.7 percent and a median of 78.2 percent. Note that the reciprocal of 0.78, which is 1.3, equals the median of the TC:EC ratio observed in these samples.

The 1.3 TC:EC ratio was the value accepted, under terms of the settlement agreement, for the purpose of temporarily converting EC measurements to TC measurements.

The median of reciprocal values is always equal to the reciprocal of the median. This relationship does not hold for the mean.

EP14AU03.007

The existing rule defines an interim TC limit of 400 μg/m

. Under the current proposal, this interim limit would be replaced with an interim EC limit of 308 μg/m

. Table VI-4 indicates the impact of this proposed change, based on the EC and TC data obtained from the 31-Mine Study. Both the 400 μg/m

TC limit and the 308 μg/m

EC limit were exceeded by about 31 to 32 percent of the samples. The difference (one sample out of 358) is not statistically significant in the aggregate. Seven samples, however, exceeded the TC limit but not the EC limit, and six samples exceeded the EC limit but not the TC limit.

Table VI-4.—Compliance With 400 μg/m

TC Limit and/or Proposed 308 μg/m

EC Limit.

[Numbers in parentheses are percentages.]

EC > 308 μg/m

TC > 400 μg/m

Yes

Total

239 (66.8)

7 (2.0)

246 (68.7)

yes

6 (1.7)

106 (29.6)

112 (31.3)

Total

245 (68.4)

113 (31.6)

358 (100.0)

C. Health Effects Literature Update

We have identified additional scientific literature pertaining to health effects of fine particulates in general and DPM in particular published subsequent to the January 19, 2001 final rule.

Table VI-5 Studies of Human Respiratory and Immunological Effects, 2000-2002

Authors, year

Description

Key results

Frew

et al.

, 2001

25 healthy subjects and 15 subjects with mild asthma were exposed to diesel exhaust (108 μg/m

) or filtered air for 2 hr, with intermittent exercise. Lung function was assessed using a computerized whole body plethysmograph. Airway responses were sampled by bronchial wash (BW), bronchoalveolar lavage (BAL), and mucosal biopsies 6 hr. after ceasing exposures

Both the asthmatic and healthy subjects developed increased airway resistance after exposure to diesel emissions, but airway inflammatory responses were different for the 2 groups. The healthy subjects showed statistically significant BW neutrophilia and BAL lymphocytosis 6 hr after exposure. The neutrophilic response of the healthy subjects was less intense than that seen in a previous study using a DPM concentration of 300 μg/m

Fusco

et al.

, 2001

Analysis of daily hospital admissions for acute respiratory infections, COPD, asthma, and total respiratory conditions in Rome, Italy

Respiratory admissions among adults were significantly correlated with CO and NO

levels, but not with suspended particles. The authors noted that since CO and NO

are good indicators of combustion products in vehicular exhaust, the detected effects may be due to unmeasured fine and ultrafine particles.

Holgate

et al.,

2002

25 healthy and 15 asthmatic subjects were exposed for 2 hours to 100 μg/m

of DPM and to filtered air on separate days. Another 30 healthy subjects were exposed for 2 hours to DPM concentrations ranging from 25 to 311 μg/m

and compared to 12 different healthy subjects exposed to filtered air. Exposure effects were assessed using lung function tests and biochemical tests of bronchial tissue samples

Healthy and asthmatic subjects exhibited evidence of bronchioconstriction immediately after exposure.

Biochemical tests of inflammation yielded mixed results but showed small inflammatory changes in healthy subjects after DPM inhalation.

Oliver

et al.

, 2001

Pulmonary function tests and questionnaire data were obtained for 359 “heavy and highway” (HH) construction workers. Intensity of DPM exposure was estimated according to job classification. Duration of exposure was estimated based on length of union membership

After adjusting for smoking and some other potential confounders, HH workers showed elevated risk of asthma. One subgroup (tunnel workers) also showed elevated risk of both undiagnosed asthma and chronic bronchitis, compared to other HH workers.

Respiratory symptoms appeared to decline with exposure duration as measured by length of union membership. The authors interpreted this as suggesting that HH workers tend to leave their trade when they experience adverse respiratory symptoms.

Salvi

et al.

, 2000

15 healthy nonsmoking volunteers were exposed to 300 μg/m

DPM and clean air for one hour at least three weeks apart

Biochemical analyses were performed on bronchial tissue and bronchial wash cells obtained six hours after each exposure

Diesel exhaust exposure enhanced gene transcription of IL-8 in the bronchial tissue and airway cells and increased IL-8 and GRO-α protein expression in the bronchial epithelium. This was accompanied by a trend toward increased IL-5 mRNA gene transcripts in the bronchial tissue. Study showed effects on chemokine and cytokine production in the lower airways of health adults. These substances attract and activate leukocytes. They are associated with the pathophysiology of asthma and allergic rhinitis.

Svartengren

et al.,

2000

Twenty nonsmoking subjects with mild allergic asthma were exposed for 30 minutes to high and low levels of engine exhaust air pollution on two separate occasions at least four weeks apart. Respiratory symptoms and pulmonary function were measured immediately before, during and after both exposure periods. Four hours after each exposure, the test subjects were challenged with a low dose of inhaled allergen. Lung function and asthmatic reactions were monitored for several hours after exposure

Subjects with PM

2.5

exposure_100 μg/m

exhibited slightly increased asthmatic responses.

Associations with adverse outcome variables were weaker for particulates than for NO

Table VI-6.—Review Articles on Respiratory and Immunological Effects, 1999-2002

Authors, Year

Description

Key results

Gavett and Koren, 2001

Summarizes results of EPA studies done to determine whether PM can enhance allergic sensitization or exacerbate existing asthma or asthma-like responses in humans and animal models

Studies indicate that PM enhances allergic sensitization in animal models of allergy and exacerbate inflammation and airway hyper-responsiveness in asthmatics and animal models of asthma.

Pandya

et al.

2002

Reviews human and animal research relevant to question of whether DPM is associated with asthma

Evidence indicates that DPM is associated with the inflammatory and immune responses involved in asthma, but DPM appears to have a far greater impact as an adjuvant with allergens than alone. DPM appears to augment IgE, trigger eosinophil degranulation, and stimulate release of numerous cytokines and chemokines. DPM may also promote the cytotoxic effects of free radicals in the airways.

Patton and Lopez, 2002

Review of evidence and mechanisms for the role of air pollutants in allergic airway diseases

Evidence suggests that air pollutants (including DPM) “affect allergic response by different mechanisms. Pollutants may increase total IgE levels and potentiate the initial sensitization to allergens and the IgE response to a subsequent allergen exposure. Pollutants also may act by increasing allergic airway inflammation and by directly stimulating airway inflammation. In addition, it is well known that pollutants can be direct irritants of the airways, increasing symptoms in patients with allergic syndromes.”

Peden, 2002

Review of “studies that exemplify the impact of ozone, particulates, and toxic components of particulates on asthma.”

DPM “may play a significant role not only in asthma exacerbation but also in T

2 inflammation via the actions of polyaromatic hydrocarbons on B lymphocytes.” “* * * PM in which the active agents are biologically active metal ions and organic residues * * * may have significant effects on asthma, especially modulating immune function, as demonstrated by the role of polyaromatic hydrocarbons from diesel exhaust in IgE production.”

Sydbom

et al.

2001

Review of scientific literature on health effects of diesel exhaust, especially the DPM components

The epidemiological support for particle effects on asthma and respiratory health is very evident; and respiratory, immunological, and systemic effects of DPM have been documented in a wide variety of experimental studies.

Acute effects of DPM exposure include irritation of the nose and eyes, lung function changes, and airway inflammation.

Exposure studies in healthy humans have documented a number of profound inflammatory changes in the airways, notably, before changes in pulmonary function can be detected. Such effects may be even more detrimental in subjects with compromised pulmonary function.

Ultrafine particles are currently suspected of being the most aggressive particulate component of diesel exhaust.

Table VI-7.—Studies Relating to Cardiovascular and Cardiopulmonary Effects, 2000-2002

Authors, Year

Description

Key Results

Lippmann

et al.,

2000

Day-to-day fluctuations in particulate air pollution in the Detroit area were compared with corresponding fluctuations in daily deaths and hospital admissions for 1985-1990 and 1992-1994

After adjustment for the presence of other pollutants, significant associations were found between particulate levels and an increased risk of death due to circulatory causes. However, relative risks were about the same for PM

2.5

and larger particles.

Magari

et al.

, 2001

Longitudinal study of a male occupational cohort examined the relationship between PM

2.5

exposure and cardiac autonomic function

After adjusting for potential confounding factors such as age, time of day, and urinary nicotine level, PM

2.5

exposure was significantly associated with disturbances in cardiac autonomic function.

Pope

et al.

, 2002

Prospective cohort mortality study, based on data collected for Cancer Prevention II study, which began in 1982

Questionnaires were used to obtain individual risk factor data (age, sex, race, weight, height, smoking history, education, marital status, diet, alcohol confounders, and occupational exposures). For about 500,000 adults, these were combined with air pollution data for metropolitan areas throughout the United States and with vital status and cause of death data through 1998

After adjustment for other risk factors potential using a variety of statistical consumption, and methods, fine particulate (PM

2.5

) exposures were significantly associated with cardiopulmonary mortality (and also with lung cancer).

Each 10-μg/m

increase in mean level of ambient fine particulate air pollution was associated with an increase of approximately 6 percent in the risk of cardiopulmonary mortality.

Samet

et al.

, 2000a, 2000b

Time series analyses were conducted on data from the 20 and 90 largest U.S. cities to investigate relationships between PM

and other pollutants and daily mortality

Results of both the 20-city and 90-city mortality analyses are consistent with an average increase in cardiovascular and cardiopulmonary deaths of more than 0.5% for every 10 μg/m

increase in PM

measured the day before death.

Wichmann

et al.

, 2000

Time series analyses were conducted on data from Erfurt, Germany to investigate relationships between the number and mass concentrations of ultrafine and fine particles and daily mortality

Higher levels of both fine and ultrafine particle concentrations were significantly associated with increased mortality rate.

Table VII.-8.—Studies and Review of Article on Cancer Effects, 2000-2002

Authors, year

Description

Key results

Boffetta

et al

, 2001

Cohort studied was entire Swedish working population (other than farmers). Job title and industry were classified according to probability and intensity of diesel exhaust exposure for years 1960 and 1970, and according to authors' confidence in assessment

Cohort members followed up for mortality for 19-year period from 1971 through 1989. Cause of death, specific cancer type, when applicable, obtained through national registries

Relative risks (RR) of lung cancer among men were 0.95, 1.1, and 1.3 for job categories with low, medium, and high exposure to diesel exhaust compared to workers in jobs classified as having no occupational exposure. Elevated risks for medium and high exposure groups were statistically significant, and no similar pattern was observed for other cancer types.

Gustavsson

et al

, 2000

Case-control study involving all 1,042 male cases of lung cancer and 2,364 randomly selected controls (matched by age and inclusion year) in Stockholm County, Sweden from 1985 through 1990. Occupational exposure, smoking habits, and other risk factors assessed based on written questionnaires mailed to subjects or next of kin. Relative Risk (RR) estimates adjusted for age, selection year, tobacco smoking, residential radon, occupational exposures to asbestos and combustion products, and environmental exposure to NO

Adjusted RR for the highest quartile of estimated lifetime exposure was 1.63, compared to the group with no exposure.

Pope

et al.

, 2002

Prospective cohort lung cancer mortality study using data collected for the American Cancer Society Cancer Prevention II Study (began 1982). Questionnaires used to obtain individual risk factor data including age, sex, race, weight, height, smoking history, education, marital status, diet, alcohol consumption, and occupational exposures. This risk factor data combined with air pollution data for metropolitan areas throughout United States and vital status and cause of death data through 1998 for about 500,000 adults

After adjusting for other risk factors and potential cofounders, chronic PM

2.5

exposures found to be significantly associated with elevated lung cancer mortality.

Each 10 g/m

increase in mean level of ambient fine particulate air pollution associated with statistically significant increase of approximately 8 percent in risk of lung cancer mortality.

Boffetta and Silverman, 2001

Meta-analysis performed on 44 independent results from 29 distinct studies of bladder cancer in occupational groups having varying exposure to diesel exhaust (studies included only if at least 5 years between first exposure and bladder cancer development). Separate quantitative meta-analyses performed for heavy equipment operators, truck drivers, bus drivers, and studies with semi-quantitative exposure assessments based on a job exposure matrix (JEM)

Overall Relative Risk (RR) was 1.37 for heavy equipment operators, 1.17 for truck drivers, 1.33 for bus drivers, and 1.13 for JEM. Quantitiatives meta-analysis also performed on 8 independent studies showing results for “high” diesel exposure. Combined results were RR=1.23 for “any exposure,” and RR=1.44 for “high exposure.”

Zeegers

et al.

, 2001

Prospective case-cohort study involving 98 bladder cancer cases among men occupationally exposed to diesel exhaust. A cohort of 58,279 men who were 55-69 years old in 1986 was followed up through 1992. Exposure assessed by job history given on self- administered questionnaire, combined with expert assessment of exposure probability. “Cumulative probability of exposure” determined by multiplying job duration by exposure probability

Four categories of relative cumulative exposure probability defined: none, lowest third, middle third, highest third. Relative risks adjusted for age, cigarette smoking, and exposure to other occupational risk factors

Relative risk for category with highest cumulative probability of exposure was 1.17.

Ojajarvi

et al

, 2000

Meta-analysis of 161 independent results (populations) from 92 studies on relationship between worksite exposures and pancreatic cancer

Based on 20 populations, no elevated risk associated with diesel exposure. Combined relative risk was 1.0. This result consistent with existing risk assessment which identified lung and bladder cancer as the only forms of cancer for which there was evidence of an association with DPM exposure.

Szadkowska-stanczyk and Ruszkowska, 2000

Literature review of studies relating to carcinogenic effects of diesel emissions. (Article in Polish; MSHA had access only to English translation of Abstract.)

Authors conclude long-term exposure (>20 years) associated with 30% to 40% increase in lung cancer risk in workers in transport industry.

Table VI-8.—Studies On Toxicological Effects of DPM Exposure, 2000-2002

Authors, Year

Description

Key results

Agent(s) of toxicity

Al-Humadi

et al.,

2002

IT instillation in rats of 5 mg/kg saline, DPM, or carbon black

Exposure to DPM or carbon black augments OVA sensitization; particle composition (of DPM) may not be critical for adjuvant effect

DPM and carbon black particles.

nger

et al.,

2000

In Vitro: assessment of content of polynuclear aromatic compounds and mutagenicity of DPM generated from four fuels, Ames assay used

Production of black carbon and polynuclear aromatic engine compounds that are mutagenic; correlation with sulfur content of fuel and engine speed

DE generated from diesel engine

DPM collected on filters and soluble organic extracts prepared.

Carero

et al.,

2001

In Vitro: assessment of DPM, carbon black, and urban particulate matter genotoxicity, human alveolar epithelial cells used

DNA damage produced, but no cytotoxicity produced

DPM, urban particulate matter (UPM), and carbon black (CB).

DPM, UPM purchased from NIST, CB purchased from Cabot.

Castranova

et al.,

2001

In Vitro: assessment of DPM on alveolar macrophage functions and role of adsorbed chemicals; rat alveolar macrophages used

In Vivo: assessment of DPM on alveolar macrophage functions and role of adsorbed chemicals, use of IT instillation in rats

DPM depresses antimicrobial potential of macrophages, thereby increasing susceptibility of lung to infections, this inhibitory effect due to adsorbed chemicals rather than carbon core of DPM

No information on generation of DPM

(details may be found in previous publications from this lab).

Fujimaki

et al.,

2001

In Vitro: assessment of cytokine production, spleen cells used

In Vivo: assessment of cytokine production profile following IP sensitization to OA and subsequent exposure to 1.0 mg/mg

DE for 12 hr/day, 7 days/week over 4 weeks, mouse inhalation model used

Adverse effects of DE on cytokine and antibody production by creating an imbalance of helper T-cell functions

DE generated from diesel engine DPM, CO

, SO

NO/NO

/NO

measured.

Gilmour

et al.,

2001

In Vivo: assessment of infectivity and allergenicity following exposure to woodsmoke, oil furnace emissions, or residual oil fly ash, mouse inhalation model used, IT instillation used in rats

Exposure to woodsmoke increased susceptibility to and severity of streptococcal infection, exposure to residual oil fly ash increased pulmonary hypersensitivity reactions

Woodsmoke, oil furnace emissions, and residual oil fly ash (ROFA) used

Hsiao

et al.

, 2000

In Vitro: assessment of cytotoxic effects (cell proliferation, DNA damage) of PM2.5 (fine PM) and PM2.5-10 (coarse PM), rat embryo fibroblast cells used

Seasonal variations in PM, in their solubility, and in their ability to produce cytotoxicity

Long-term exposure to non-killing doses of PM may lead to accumulation of DNA lesions

PM collected Hong Kong area and solvent- extractable organic compounds used.

Kuljukka-Rabb

et al.

, 2001

In Vitro: assessment of of adduct formation following exposure to DPM, DPM extracts, benzo[a]pyrene, or 5-methyl-chrysene, mammary carcinoma cells used

Temporal and dose-dependent DNA adduct formation by PAHs

Carcinogenic PAHs from diesel extracts lead to stable DNA adduct formation

Some DPM purchased from NIST, some DPM collected on filters from diesel vehicle, and solvent-extractable organic compounds used.

Moyer

et al.

, 2002

In Vivo: 2-phase retrospective study, review of NTP data from 90-day and 2-yr exposures to particulates, use of mouse inhalation model

Induction and/or exacerbation of arteritis following chronic exposure (beyond 90-day) to particulates

Indium phosphide, cobalt sulfate heptahydrate, vanadium pentoxide, gallium arsenide, nickel oxide, nickel subsulfide, nickel sulfate hexahydrate, talc, molybdenum trioxide used.

Saito

et al.

, 2002

In Vivo: assessment of cytokine expression following exposure to DE (100 μg/m3 or 3 mg/m3 DPM) for 7-hrs/day × 5 days/wk × 4 wks, mouse inhalation model used.

DE alters immunological responses in the lung and may increase susceptibility to pathogens, low-dose DE may induce allergic/asthmatic reactions

DE generated from diesel engine DPM, CO, SO2, and NO2 measured.

Sato

et al.

, 2000

In Vivo: assessment of mutant frequency and mutation spectra in lung following 4-wk exposure to 1 or 6 mg/m

DE, transgenic rat inhalation model used

DE produced lesions in DNA and was mutagenic in rat lung

DE generated from light-duty diesel engine

Concentration of suspended particulate matter (SPM) measured, 11 PAHs and nitrated PAHs identified and quantitated in SPM.

Van Zijverden

et al.,

2000

In Vivo: assessment of immuno-modulating capacity of DPM, carbon black, and silica particles, mouse model used (sc injection into hind footpad)

DPM skew immune response toward T helper 2 (Th2) side, and may facilitate initiation of allergy

DPM, carbon black particles (CBP) and silica particles (SIP) used.

DPM donated by Nijmegen University, CBP and SIP purchased from BrunschwichChemie and Sigma Chemical Co., respectively.

Vincent

et al.,

2001

In Vivo: assessment of cardiovascular effects following 4-hr exposure to 4.2 mg/m

diesel soot, 4.6 mg/m

carbon black, or 48 mg/m

ambient urban particulates, rat inhalation model used

Increases in endothelin -1 and -3 (two vasoregulators) following ambient urban particulates and diesel soot exposure

Small increases in blood pressure following exposure to ambient urban particulates

Diesel soot, carbon black and urban air particulates used.

Diesel soot purchased from NIST, carbon black donated by University of California, urban air particulates collected in Ottawa.

Walters

et al.,

2001

In Vivo: assessment of airway reactivity/responsiveness, and BAL cells and BAL cytokines following exposure to 0.5 mg/mouse aspirated DPM, ambient PM, or coal fly ash

Dose and time-dependent changes in airway responsiveness and inflammation following exposure to PM

Increase in BAL cellularity following exposure to DMP, but airway reactivity/ unchanged

DPM, PM, and coal fly ash used.

DPM purchased from NIST, PM collected in Baltimore, and coal fly ash obtained from Baltimore power plant.

Whitekus

et al.,

2002

In Vitro: assessment of ability of six antioxidants to interfere in DPM-mediated oxidative stress, cell cultures used

In Vivo: assessment of sensitization to OA and/or DPM and possible modulation by thiol antioxidants, mouse inhalation model used

Thio antioxidants (given as a pre-treatment) inhibit adjuvant effects of DPM in the induction of OA sensitization

DE generated from light-duty diesel engine, DPM collected, dissolved in saline, and aerosolized.

*Key:

(A) immunological and/or allergic reactions.

(B) inflammation.

(D) Induction of free oxygen radicals.

(E) airflow obstruction.

(F) impaired clearance.

(G) reduced defense mechanisms.

(H) adverse cardiovascular effects.

Table VI-9.—Review Articles on Toxicological Effects of DPM Exposure, 2000-2002

Authors, Year

Description

Conclusions

Agent(s) of toxicity

ILSI Risk Science Institute Workshop Participants, 2000

Review of rat inhalation studies on chronic exposures to DPM and to other poorly, soluble nonfibrous particles of low acute toxicity that are not directly genotoxic

No overload of rat lungs at lower lung doses of DPM and no lung cancer hazard anticipated at lower doses

Poorly soluble particles, nonfibrous particles of low acute toxicity and not directly genotoxic (PSPs)

Nikula, 2000

Review of animal inhalation studies on chronic exposures to DE, carbon black, titanium dioxide, talc and coal dust

Species differences in pulmonary retention patterns and lung tissue responses following chronic exposure to DE

DE, carbon black, titanium dioxide, talc and coal dust

Oberdoerster, 2002

In Vivo: review of toxicokinetics and effects of fibrous and nonfibrous particles

High-dose rat lung tumors produced by poorly soluble particles of low cytotoxicity (

e.g.,

DPM) not appropriate for low-dose extrapolation (to humans); lung overload occurs in rodents at high doses

Fibrous particles, and nonfibrous particles that are poorly soluble and have low cytotoxicity (PSP)

Veronesi and Oortigiesen, 2001

In Vitro: review of nasal and pulmonary innervation (receptors) and pulmonary responses to PM, mainly BEAS cells and sensory neurons used

Pulmonary receptors stimulated/activated by PM, leading to inflammatory responses

PM: residual oil fly ash, woodstove emissions, volcanic dust, urban ambient particulates, coal fly ash, and oil fly ash.

* Key:

(A) immunological and/or allergic reactions.

(B) inflammation.

(D) Induction of free oxygen radicals.

(E) airflow obstruction.

(F) impaired clearance.

(G) reduced defense mechanisms.

(H) adverse cardiovascular effects.

VII. Feasibility

A. Background on Feasibility

Section 101(a)(6)(A) of the Federal Mine Safety and Health Act of 1977 (Mine Act) requires the Secretary of Labor to establish health standards which 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 lifetime. Such standards must be based upon:

Research, demonstrations, experiments, and such other information as may be appropriate. In addition to the attainment of the highest degree of health and safety protection for the miner, other considerations shall be the latest available scientific data in the field, the feasibility of the standards, and experience gained under this or other health and safety laws. Whenever practicable, the mandatory health or safety standard promulgated shall be expressed in terms of objective criteria and of the performance desired. (Section 101(a)(6)(A)).

The legislative history of the Mine Act states:

This section further provides that “other considerations” in the setting of health standards are “the latest available scientific data in the field, the feasibility of the standards, and experience gained under this and other health and safety laws.” 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 v. Brennan, 530 F.2d 109 (3d Cir. 1975); Society of Plastics Industry v. 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 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. S. Rep. No. 95-181, 95th Cong. 1st Sess. 21 (1977).

Though the Mine Act and its legislative history are not specific in defining feasibility, the courts have clarified the meaning of feasibility. The Supreme Court, in

American Textile Manufacturers' Institute

Donovan

(OSHA Cotton Dust), 452 U.S. 490, 508-509 (1981), defined the word “feasible” as “capable of being done, executed, or effected.”

In promulgating standards, hard and precise predictions from agencies regarding feasibility are not required. The “arbitrary and capricious test” is usually applied to judicial review of rules issued in accordance with the Administrative Procedures Act. The legislative history of the Mine Act 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).

Thus, MSHA must base its predictions on reasonable inferences drawn from existing facts. 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 the 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.

B. Technological Feasibility

At this stage of the rulemaking, MSHA concludes that a permissible exposure limit of 308 micrograms of EC per cubic meter of air (308

μg/m

) is technologically feasible for the metal and nonmetal underground mining industry. 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.

United Steelworkers of America, AFL-CIO-CLC

Marshall,

(OSHA Lead) 647 F.2d 1273 (D.C. Cir. 1981) cert. denied, 453 U.S. 918 (1981) (citing

American Iron and Steel Institute

OSHA

, (AISI-I) 577 F.2d 825 (3d Cir. 1978) at 834; and,

Industrial Union Dep't., AFL-CIO

Hodgson

, 499 F.2d 467 (D.C. Cir.1974)). The existence of general technical knowledge relating to materials and methods which may be available and adaptable to a specific situation establishes technical feasibility. A control may be technologically feasible when Aif 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 (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, AFL-CIO-CLC

Marshall,

(OSHA Lead) 647 F.2d 1164.

MSHA has established that technology is available that can accurately and reliably measure miners' exposures to DPM in all types of underground metal and nonmetal mines. MSHA intends to sample miners' exposures by using a respirable dust sampler equipped with a submicrometer impactor and analyze samples for the amount of elemental carbon using the NIOSH Analytical Method 5040, or any other method that NIOSH determines gives equal or improved accuracy, as stated in existing § 57.5061(b) and in this proposed rule.

MSHA is changing the surrogate that it uses to measure DPM exposures from total carbon (TC) to elemental carbon (EC). This change will avoid interferences associated with organic carbon that could collect on the filter and increase the likelihood of contaminating the sample with OC from non-diesel sources. MSHA agreed to propose this change as dictated by the DPM Settlement Agreement and the entire mining community supports this change.

Control mechanisms also exist that are capable of reducing DPM exposures to the interim PEL of 308 micrograms in all types of underground metal and nonmetal mines. MSHA believes that mine operators will choose from various control options that are currently available, including diesel particulate filter (DPF) systems, ventilation upgrades, oxidation catalytic converters, alternative fuels, fuel aditives, enclosures such as cabs and booths, improved maintenance procedures, newer engines (less DPM emitting), and various work practices and administrative controls. MSHA has given the mining industry flexibility in selecting DPM control options that best suit the mine operator's specific needs.

Based on the current information in the rulemaking record, MSHA concludes that it has a technologically feasible measurement method that operators and the Agency can use to accurately determine if miners' exposures exceed the limit. Both control mechanisms and the DPM sampling method are discussed elsewhere in this preamble. MSHA believes that the proposed standard would adequately address feasibility issues in one of two ways:

(1) Pursuant to § 57.5060(a) and (d) of the proposed rule. If MSHA determines that feasible engineering and administrative controls are being installed, used, and maintained and still do not reduce a miner's exposure to the limit, mine operators would be required to supplement controls with a respiratory protection program; or,

(2) Mine operators may apply to the MSHA district manager for approval for an extension of time in which to reduce miners' exposures to the DPM limit. MSHA is not proposing any maximum limit on the number of extensions an operator may have, since MSHA's decision hinges upon feasibility.

The proposal permits operators greater flexibility in complying with the DPM limit, contrary to the existing prohibition against using administrative controls and respiratory protection. Mine operators who need on-site technical assistance should contact the respective MSHA district manager for assistance. MSHA will continue to assist mine operators in special mining situations that could affect the successful use of DPM filters.

Section IV above contains the executive summary of the 31-Mine Study. As that section explains, the technical feasibility analyses in the 31-Mine Study were based on the highest DPM sample result obtained at each

mine and on all major DPM emission sources at each mine in addition to spare equipment. The study found that five mines were already in compliance with the interim concentration limit, and another two mines were already in compliance with the existing lower, final concentration limit.

MSHA predicted that eleven of the 31 mines could achieve compliance with both limits through installation of DPM filters alone. Ventilation upgrades were specified for only 5 of the 31 mines in this study, and then only to achieve the final concentration limit. MSHA projected that compliance with the interim and final concentration limits could be achieved without requiring major ventilation installations such as new main fans and repowering main fans. In the existing standard, the agency based its feasibility projections on an average DPM concentration level of over 800 μg/m

. MSHA believes that miners' exposures are now much lower, probably as a result of the introduction of clean engines, better maintenance, and the elimination of interferences as confirmed by MSHA's compliance assistance baseline sampling.

MSHA collected baseline samples at most underground mines with diesel powered equipment. Samples were collected in the same manner as MSHA intends to sample for enforcement under the proposed rule. MSHA found the average exposure (based on EC × 1.3) in the baseline sampling to be 222 μg/m

resulting in greater compliance feasibility with the proposed rule.

In spite of the concentrations observed in the 31-Mine Study, the industry parties in the litigation continued to stress that compliance with the existing standard was infeasible in that DPF systems could not be retrofitted properly and could not effectively achieve regeneration. Some operators also noted that they experienced difficulty in ordering and obtaining DPF systems. MSHA could not confirm these statements, but during the 31-Mine Study, the Agency did not find that mine operators were using filtration devices. Moreover, few mine operators actually contacted MSHA to ask for compliance assistance visits, in spite of the Agency's repeated offers to help. Once MSHA initiated its comprehensive compliance assistance work at underground mine sites, the Agency found that most mines did not have complete information on the available control technologies. Accordingly, MSHA stated in its final report on the 31-Mine Study regarding feasibility:

Compliance with both the interim and final concentration limits may be both technologically and economically feasible for metal and nonmetal underground mines in the study. MSHA, however, has limited in-mine documentation on DPM control technology. As a result, MSHA's position on feasibility does not reflect consideration of current complications with respect to implementation of controls such as retrofitting and regeneration of filters. MSHA acknowledges that these issues influence the outcome of feasibility of controls. The agency is continuing to consult with NIOSH, industry and labor representatives on the availability of practical mine worthy filter technology.

Since this finding, however, MSHA and NIOSH have been working with the metal and nonmetal underground mining community and equipment manufacturers to continually refine and improve application of existing DPM control technology. The Agency has made considerable strides in resolving mine operators' concerns with the mine worthiness of DPF systems.

During data collection for the 31-Mine Study, mine operators also questioned the performance of the SKC sampler, especially in light of modifications to it. Additionally, some commenters requested that MSHA revise its internal sampling methodology and analysis for inspectors and laboratory personnel.

MSHA disagrees. One of the objectives of the 31-Mine Study was to examine the performance of the SKC sampler. The Agency is satisfied with the performance of the SKC cassette in collecting DPM while avoiding mineral dust. NIOSH's laboratory and field data show that the SKC cassette collected DPM efficiently. Under a side protocol of the 31-Mine Study, MSHA tested the efficiency of the SKC cassette in avoiding mineral dust at four mines. In these tests, no mineral dust was measured on the filters of the SKC samplers. This finding was confirmed by NIOSH laboratory tests. However, NIOSH discovered that in many cases, the DPM deposit area was irregular in shape, and the shapes varied among samples. Since the DPM deposit area is used to calculate carbon concentrations attributed to DPM, the varied shapes can cause an error in determining DPM concentrations. With the cooperation of MSHA and the technical recommendations and extensive experimental verification by NIOSH, SKC was able to modify the cassette design to produce a consistent and regular DPM deposit area, satisfactorily resolving the problem.

The fact that the deposit area was assumed constant when in fact there were variations in the boundary (shape) and area of deposit of the SKC cassette samples taken in the 31-Mine Study affects only the reported concentrations of the carbon values (EC, OC, and TC) because deposit area is used in concentration calculation. The results of the inter-laboratory and intra-laboratory studies that compared the analysis of the punches of those (or any) filters from the SKC cassette are unaffected for two reasons: (1) The deposit area does not enter into the calculations (surface densities of carbon in ug/cm

were compared), and (2) the punches were taken from filters inside the boundary of the area of deposits, where the deposits were uniform.

In their comments to the ANPRM, mine operators continued to emphasize the need for more research on control technology. Additionally, NIOSH commented:

In conclusion, various manufacturers offer the particulate filters for diesel engines rated from 15 to several hundred hp. Although on the market for more than a decade, DPF systems have been only sporadically deployed and tested on underground mining vehicles. The DEEP-sponsored evaluation tests at Noranda BM&S and INCO Stobie Mines are based on our knowledge, the best organized attempts to evaluate DPFs in the underground environment. The results from these tests reveal that the DPF systems that have been evaluated on heavy-duty vehicles powered by engines rated over 277 hp and on light duty vehicles powered by 50 hp engines offer promising technology. However, this technology needs significant additional evaluation and some possible re-engineering for underground mining applications. In-use deficiencies, secondary emissions, engine backpressure, DPF regeneration, DPF reliability and durability are major issues requiring additional research and engineering. In addition, it is been found that deployment of most systems, particularly those which require active means of regeneration, require major changes in miners' attitudes toward engine and DPF maintenance. NIOSH's DEEP experienced showed that emission-based engine maintenance, greater discipline on the part of the vehicle operator, and better operational logistics (

e.g.

, multiple locations of regeneration stations for a single vehicle) are imperative for success of DPF technology.

To the contrary, the NIOSH comments in response to the ANPRM include a summary of their experience with retrofitting existing diesel powered equipment. NIOSH acknowledges that although diesel particulate filters have been available to U.S. mines for many years, they have not been extensively used and documented. NIOSH states that in-mine experience with filters is limited, but NIOSH also related their experience with the Diesel Emissions Evaluation Program (DEEP) in Canada. NIOSH stated:

[The DEEP program] has shown that these filters have significant potential for reducing DPM exposure of miners, but that there are numerous technical and operational issues that need to be addressed through research and in-mine evaluations before they can be readily implemented on a broad-based scale in U.S. mines.

MSHA has found that most mine operators can successfully resolve their implementation issues if they make informed decisions regarding filter selection, retrofitting, engine and equipment deployment, operations, and maintenance. The Agency recognizes that practical mine-worthy DPF systems for retrofitting most existing diesel powered equipment in underground metal and nonmetal mines are commercially available and are mine worthy to effectively reduce miners' exposures to DPM. MSHA also recognizes that installation of DPF systems will require mine operators to work through technical and operational situations unique to their specific mining circumstances. In view of that, MSHA has provided comprehensive compliance assistance to the underground metal and nonmetal mining industry.

Commenters to the ANPR responded to the question of changing a diesel engine model to accommodate a control device by stating that anything other than the original engine model is essentially incompatible and would require prohibitive design engineering analysis and implementation. MSHA agrees that it may not be feasible to change engines on some diesel powered equipment. However, as engine manufacturers develop cleaner engines over time, they are phasing out older models and newer, cleaner engine models are available from the same engine manufacturer. In some cases, the new engine models are direct replacements for an older model. The benefits of retrofitting a machine with a cleaner engine are better fuel economy, less DPM emitted from the tailpipe, better lubrication systems, and better diagnostic tools, especially with the electronic engines. A cleaner engine that emits less DPM will deposit less DPM on the filter, thus permitting more time between regeneration, especially in active regeneration systems or combination active/passive regeneration systems.

Filter Workshops

Recently, government, labor and industry sponsored two workshops on “Diesel Emissions and Control Technologies in Underground Metal and Nonmetal Mines” held in Cincinnati, Ohio, on February 27, 2003, and Salt Lake City, Utah, on March 4, 2003. These workshops focused on implementation of DPM control technologies capable of reducing DPM exposures to particulate matter and gaseous emissions from diesel-powered vehicles that are presently available to the underground metal and nonmetal mining industry in this country. The workshops provided an excellent forum for open discussion and the exchange of ideas and experiences relative to the use of diesel powered equipment in underground mines.

At the workshops, industry experts discussed issues pertaining to the installation and use of DPFs in underground mines. Application of technology and mine operators' experiences with using filters on their diesel powered equipment are becoming more commonplace in the mining industry since the promulgation of the DPM rule.

MSHA, NIOSH, and industry speakers presented their first-hand experiences with the implementation and use of diesel particulate filters in underground mines since promulgation of the existing DPM rule. Major diesel filter manufacturers and vendors of control technologies and engines also participated in the workshops.

NIOSH compiled a summary report to capture presentations, comments and discussions rendered at the workshops, including comments offered by industry representatives who shared their experiences with the effectiveness of DPM filters. MSHA believes that NIOSH's account of the workshops helps to demonstrate feasibility of control technology measures that mine operators have found beneficial and effective. MSHA mailed copies of the NIOSH report to mine operators covered by the proposed rule. This information also is available on the NIOSH Diesel List Server. At the workshops, the following information was discussed:

DPF Efficiency:

Laboratory and field studies indicate that filtration efficiency for elemental carbon is above 95% and perhaps is as high as 99%.

MSHA worked with NIOSH at MSHA's laboratory to determine the efficiency of several ceramic filters. MSHA ran steady state tests on the dynamometer and collected DPM samples for NIOSH 5040 analysis. The results of the filter tests showed efficiency results close to 99% for elemental carbon. NIOSH commented:

The INCO project includes two Kubota M5400 tractors powered by Kubota F2803B 50 hp engines [Stachulak 2002]. Both are fitted with actively regenerated DPFs that have a silicon carbide (SiC) filter core. The SiC cores come from the same manufacturer; the DPF systems are supplied by different manufacturers. The filtration efficiency at the tailpipe is >99 percent for EC as determined by NIOSH using the EchoChem Analytics PAS 2000 carbon particle analyzer. One DPF system uses active on-board regeneration; electric heating coils are integrated into the unit and the unit is plugged into a regeneration controller mounted off board. The other unit is an active off-board system in which the DPF is removed from the vehicle and exchanged with the previously regenerated filter. The soot-laden filter is placed in a regeneration station. Both vehicles are assigned to “special groups” of individuals who ensure that the regenerations are performed as needed.

MSHA stated in the preamble to the January 19, 2001 Final Rule that filter efficiency for cordierite and silicon carbide media used in many DPF systems is 85% and 87% respectively for diesel DPM. These efficiencies were based on whole diesel particulate as collected per part 7, subpart E specifications for measuring DPM. The mining industry has expressed concern that laboratory results do not reflect the real world in both duty cycle and operational environment, so the Metal and Nonmetal Diesel Partnership and MSHA will conduct a set of in-mine tests before mid-2003.

DPF Selection:

To use DPF systems successfully, mine operators must do their homework prior to ordering DPF systems. It is critical for filter performance and efficiency to match the filters to the diesel powered equipment and consider how the equipment is to be used in the underground mine. Mine operators should assume that every application is unique.

Following promulgation of the existing DPM rule, most mine operators were unaware that filter selection involves consideration of these factors. Therefore, in February 2003, MSHA and NIOSH posted on their web sites a comprehensive compliance assistance tool titled “A DPM Filter Selection Guide for Diesel Equipment In Underground Mines” (Filter Selection Guide). The guide provides mine operators with detailed step-by-step considerations in selecting DPF system compatible with the specific equipment. Also, the Filter Selection Guide provides information on modifications and adjustments to diesel powered equipment that mine operators may have to make to successfully apply DPF systems.

Mine operators should start by making certain that they are properly maintaining their engines and not consuming excessive amounts of crankcase oil. The mine operator may then obtain exhaust temperature logs or traces for several shifts, and use these

traces to select the DPF systems with the regeneration options that will work for that piece of equipment. Exhaust temperature traces can be analyzed by mine personnel or given to several DPF suppliers to use to provide the operator with options.

Exhaust temperatures govern the DPF regeneration options. These options are provided in the Table VII-1.

Table VII-1.—DPF Regeneration Options

Temperature that the exhaust exceeds 30% of the time, degrees C

DPF system (media consists of cordierite or silicon carbide ceramic)

Comments

>550

Uncatalyzed media

Rarely, if ever, occurs.

>390-420

Base metal catalyzed cordierite

No increase in NO

>340

Lightly platinum catalyzed ceramic with CDT fuel additive

Special provisions must be made to ensure additive is always present in fuel and that equipment w/o DPFs cannot be fueled with additive-containing fuel. No increase in NO

>325

Platinum catalyzed ceramic

Lab results indicate significant NO to NO

conversion; field results are mixed.

>Any temperature below 325

Active (Manually) regenerated system

Insufficient exhaust temperature to support spontaneous regeneration during shift. DPFs are regenerated in place with equipment off-duty or DPF is swapped out.

As Table VII-1 shows, a DPF system will function successfully at or above an exhaust gas temperature specified by the manufacturer's regeneration temperature, that is, an active regenerating system will work at all exhaust temperatures, and a platinum catalyzed system at any temperature above 325°C. However, these exhaust gas temperatures must be achieved at least 30% of the time during the day to be sufficient for passive regeneration. In addition, the tune of the engine will also be a factor for proper regeneration. If an engine goes out of tune and begins to emit higher DPM concentrations in the exhaust, the exhaust backpressure may increase more quickly. Therefore, it is recommended that mine operators install backpressure devices on machines equipped with filters in order to properly monitor the condition of the filter and regeneration of the filter.

Table VII-1 also provides information in the “Comments” column on the effect of the filters coated with a catalyst on NO

emissions. MSHA has tested in their laboratory the types of filters listed and has posted on its Web site a list of the filters that can cause NO

increases from the engine and those catalytic formulations that do not significantly increase NO

is formed from NO in the engine's exhaust in the presence of the catalyst. This reaction occurs at exhaust gas temperatures at approximately 325°C. This temperature is also the temperature at which the platinum catalyst will allow for passive regeneration. Filter manufacturers have normally wash-coated their filters with large amounts of platinum to make sure that the filters will regenerate. This large concentration of platinum, in combination with longer retention time of the exhaust gas in the filter, results in the formation of NO

. Manufacturers have been looking at wash-coat formulations containing less platinum loading to lower the NO

effects. Catalytic converters are also wash-coated with platinum, however, the loading used on catalytic converters is lower than ceramic filters. Due to faster movement of the exhaust gas through the catalytic converter compared to the ceramic filter, the effect of NO

increase is minimized.

MSHA is not aware of overexposures to NO

with the use of those catalyzed traps that MSHA has identified. MSHA issued a Program Information Bulletin (PIB 02-04, May 31, 2002) which alerted mine operators that catalyzed traps identified on our Web site could increase NO

. Mine operators were advised to conduct sampling for NO

when these filters were used to ensure miners' are not overexposed or that the filters were causing a general increase of NO

in the mine's ambient environment. Mine operators who use catalyzed filters (which have the potential to increase NO

) should have ventilation systems that are able to remove or dilute the NO

to a non-hazardous concentration. However, operators must be aware of localized areas where NO

could build up more quickly and create a health hazard for exposed miners.

As discussed in the Greens Creek report, the use of catalyzed filters on those machines used in the study did not indicate any substantial increase in NO

. MSHA is continuing to work with filter manufacturers to evaluate catalytic formulations on NO

generation from the exhaust.

Active regeneration systems discussed below are normally not catalyzed which would then not produce an increase in NO

. As stated above, NO

is generated when exhaust gas temperatures are normally high enough for passive regeneration. If the filter can passively regenerate, then there is a potential for increases in NO

emissions.

Table VII-2.—Scenarios for Active Regeneration

System name

Regenerating location

Regenerating controller location

Comments

On-board-On-board

On Equipment

Requires source of electric power, normally 440 or 480 VAC.

On-board-Off-board

On Equipment

Designated and fixed-location

Requires equipment to come to a specific regeneration site.

Off-board

Off equipment

Fixed-location

DFPs are exchanged and must be small enough to be handled by one person. Increases number of DPFs needed.

On-board fuel burner

On-equipment

On-equipment during operation

System is complex yet provides advantages of operating during equipment use; manufacture has been discontinued.

Scenarios for active regeneration systems are listed in Table VII-2. The first two systems listed in Table VII-2 may require sufficient machine down time for regeneration, which is usually about one hour between shifts. Also, the equipment should be parked at a designated location during the regeneration period. MSHA recognizes that presently in some mines, production equipment is not brought to a specific location at the end of a shift. At mines where this occurs, mine operators may need to make changes to accommodate such DPF regeneration designs. Alternatively, mine operators may choose to have the equipment operator remove the DPF at the end of each shift and have the next operator replace it with a regenerated unit at the start of the shift. In short, mine operators must plug in the regeneration system at the end of the shift, or DPFs must be transported from the regeneration area to the equipment location. Multiple filters may be installed on a machine in the place of one filter in order to decrease the size and weight of the filters.

Under certain circumstances, some passive DPF systems have exhibited marginal regeneration. This is due to the fact that the duty cycle exhaust temperature is such that some but not all of the DPM is removed during the normal work shift. Slowly the DPM builds up until the DPF must be regenerated manually. In some instances, this needs to be done every 250 hours which would coincide with the regular preventive maintenance cycle for diesel powered equipment.

Achieving a long service life:

The key to achieving a long service life from any DPF is to monitor and strictly adhere to exhaust back pressure limits and taking action appropriately. Passive regenerating systems are especially sensitive to equipment duty cycle. A change in duty cycle may reduce exhaust temperatures to a point that regeneration does not spontaneously occur. It is crucial that prompt attention is given to this situation and it is remedied before exhaust backpressures even reach the specified backpressure limit. Continuing to operate with an increasing exhaust backpressure will lead to overloading the DPF with soot. When regeneration is initiated, the large mass of soot may create temperatures hot enough to crack or melt the filter element, thus compromising the filter's efficiency. A similar scenario applies to active systems. Failure to timely regenerate the filter will cause increases in back pressure during a production shift which, if continued, will cause loss of engine power and may invalidate engine warranties.

Thermal runaway may also occur during manual regeneration. Because of the build up of ash, an unburnable component of diesel soot arising from burning lubrication oil, the baseline back pressure of any DPF will rise slowly. Approximately every 1,000 hours, the DPF should be cleaned of the ash following the manufacturer's procedure.

Engine malfunctions and effects on DPF:

Normally in mining, engine malfunctions are indicated by excessively smoky exhaust. That indicator will not occur with DPF systems. Malfunctions such as excessive soot emissions, intake air restriction, fouled injector, and over-fueling, may result in an abnormal rise in back pressure in systems that do not spontaneously regenerate. Also, these conditions could lead to abnormal changes in back pressure in passive systems because the malfunction may raise exhaust temperatures causing the excess soot to be burned off. These malfunctions may be detected during the usual 250-hour maintenance and emissions checks conducted upstream of the DPF using carbon monoxide (CO) as an indicator.

The other major filter malfunction is excessive oil consumption that is sometimes associated with blue smoke that could be masked by the performance of the DPF. However, excessive oil consumption leads to a rapid increase in baseline backpressure due to ash accumulation. Excessive oil consumption can be detected if records are kept on oil usage.

Detecting malfunctioning DPF:

As noted above, the DPF can be damaged mainly by thermal events such as thermal runaway. Shock, vibration, or improper “canning” of the filter element in the DPF can also lead to leaks around the filter element. A Bacharach/Bosch smoke spot test can be used to verify the integrity of a DPF. Smoke spot numbers below “1” indicate a good filter; smoke numbers above “2” indicate that the DPF may be cracked or leaking. Smoke spot and CO tests during routine 250 hour preventative maintenance is a good diagnostic practice. Note that although a smoke spot number above “2” may indicate a cracked or leaking filter, such a result does not necessarily mean the filter has “failed” and is not functioning adequately. In MSHA evaluations of DPF performance at the Greens Creek mine, filters that tested with smoke numbers above “2” were still shown to be over 90% effective in capturing elemental carbon, based on subsequent NIOSH 5040 analysis of the smoke spot filters.

Some commenters have suggested that diesel particulate filters are not a feasible DPM control option because they are not commercially available for the full range of engine horsepowers used in underground metal and nonmetal mining equipment, especially low horsepower units (less than 50 hp) and high horsepower units (greater than 250 hp). MSHA has found that suitable DPFs for engines of the horsepowers used in underground metal and nonmetal mining equipment are commercially available. The following discussion addresses low horsepower and high horsepower applications, respectively.

Low horsepower engines ranging from around 5 horsepower to around 100 horsepower are frequently used in ancillary and support mining equipment such as personnel transports, utility tractors, “gators,” fork lifts, pumps, welders, compressors, and similar equipment, both mobile and stationary. The duty cycle of this type of equipment

is not sufficient to support passively controlled regeneration of a DPF. Thus, either on-board or off-board active filter regeneration is necessary.

In sizing an actively regenerated filter for these small horsepower engines, the only significant selection criterion is the desired time interval between active regenerations. For example, if the user wishes to regenerate a filter no more often than once per day, then the filter must have the capacity to store the maximum amount of soot generated by the subject engine over the period of one day while maintaining acceptable engine backpressure. If physical space to mount a filter is limited, the smallest filter having adequate soot storage capacity at the maximum acceptable backpressure would be selected. If space constraints are not an issue, a larger capacity filter would also be acceptable, with the larger size permitting a longer time interval between regenerations.

As a point of reference, a once-per-day actively regenerated DPF for a 60 hp personnel transport tractor operated for one shift per day is about 20 inches long by about 10 inches in diameter, and such filters are commercially available from multiple sources. If the same filter is fitted to a 30 hp engine having the same duty cycle and emission rate (expressed as g/bhp-hr), that filter will function just as well, but the time interval between regenerations would roughly double. Based on this DPF selection process, there is probably no lower limit to the size engine that can be effectively filtered using any of several commercially available active systems.

DPFs for low horsepower engines can also be provided by the original equipment manufacturer (OEM) or distributor as standard or optional equipment. An example is a Series 7 Toyota forklift equipped with a 40 hp 1DZ-II diesel engine for which a DPF-II diesel particulate filter is offered as an OEM or dealer-installed option. The DPF unit is about 14-inches long and about 8-inches in diameter, and is mounted on the rear of the forklift body.

Regarding high horsepower applications of DPF systems, for purposes of this discussion, “high” horsepower is meant to include engines of 250 horsepower and higher because this is the horsepower range addressed by the commenter. Engines of this size would typically be installed on production equipment such as loaders and haulage trucks and are commercially available from several manufacturers.

There are two approaches to filtering diesel particulate emissions that can be implemented on high horsepower engines using current commercially available DPF units: large capacity single unit DPFs; and multiple DPFs that are either manifolded to the same exhaust pipe, or separate DPFs that are provided on each side of a dual exhaust system.

An example of a large capacity single unit DPF system is the Engelhard model 9121A 15-inch long by 15-inch diameter Pt-catalyzed filters installed on the LHD and haulage trucks that were the subject of MSHA's compliance assistance diesel emissions tests at the Greens Creek mine. The LHD and all three haulage trucks were equipped with the same MSHA Approved 12.7 L engines rated at 475 hp at 2100 rpm. The LHD engine was derated to 300 hp, but this value still exceeds the commenter's threshold level of concern of 250 hp, and the truck engines were generating the full 475 hp. These DPFs passively regenerated on both the loader and haulage trucks, and the emission testing demonstrated filter efficiencies of greater than 90%.

The other approach to filtering high horsepower engines is to provide multiple filters. When an engine's exhaust is routed through a single exhaust pipe, the exhaust can be split into two parallel paths, with each path being equipped with a filter. When an engine has a dual exhaust system (

i.e.

separate exhaust pipes on either side of the engine, which is the most common arrangement on high horsepower engines), a DPF can be fitted to each exhaust pipe. This approach actually simplifies a DPF installation on an engine with dual exhausts, as installing a single filter would require modification of the exhaust system to join together the dual exhausts into a single exhaust pipe upstream of the filter. On underground equipment where space is at a premium, it may be easier to install two smaller filters than to find a space large enough to install one large filter.

Depending on the horsepower of an engine, space constraints, method of filter regeneration, and other factors, it may be necessary to split an engine's exhaust into more than two parallel paths for DPF installation. For example, each side of a dual exhaust system could be split into two parallel paths to facil

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