# Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A05-10681 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** June 6, 2005 - **Citation:** 70 FR 32868 ## Text DEPARTMENT OF LABOR Mine Safety and Health Administration 30 CFR Part 57 RIN 1219-AB29 Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners AGENCY: Mine Safety and Health Administration (MSHA), Labor. ACTION: Final rule. SUMMARY: This final rule revises MSHA's existing standards addressing diesel particulate matter (DPM) exposure in underground metal and nonmetal (M/NM) mines. In this final rule, MSHA changes the 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. Also, this final rule increases flexibility of compliance for mine operators by requiring MSHA's longstanding hierarchy of controls for its other exposure-based health standards at M/NM mines, but retains the prohibition on rotation of miners for compliance. Furthermore, this final rule: Requires MSHA to consider economic as well as technological feasibility in determining if operators qualify for an extension of time in which to meet the final DPM limit; deletes the requirement for a control plan; and makes conforming changes to existing provisions concerning compliance determinations, environmental monitoring and recordkeeping. DATES: Effective Date: The final rule is effective on July 6, 2005. FOR FURTHER INFORMATION CONTACT: Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson Blvd., Room 2350, Arlington, Virginia 22209-3939; 202-693-9440 (telephone); or 202-693-9441 (facsimile). You may obtain copies of this final rule and the Regulatory Economic Analysis (REA) in alternative formats by calling 202-693-9440. The alternative formats available are either a large print version of these documents or electronic files that can be sent to you either on a computer disk or as an attachment to an e-mail. The documents also are available on the Internet at http://www.msha.gov/REGSINFO.HTM . SUPPLEMENTARY INFORMATION: Outline of Preamble This outline will assist the mining community in finding information in this preamble. I. List of Common Terms II. Rulemaking Background A. First Partial Settlement Agreement B. Second Partial Settlement Agreement III. The Final PEL IV. The 31-Mine Study A. Summary B. Subsequent Activities V. Compliance Assistance A. Baseline Sampling B. DPM Control Technology VI. DPM Exposures and Risk Assessment A. Introduction B. DPM Exposures in Underground M/NM Mines C. Health Effects D. Significance of Risk VII. Feasibility A. Background B. Technological Feasibility C. Economic Feasibility VIII. Summary of Costs and Benefits IX. Section-by-Section Analysis X. Distribution Table XI. Regulatory Impact Analysis XII. References Cited I. List of Common Terms Listed below are the common terms used in the preamble. Commission Federal Mine Safety and Health Review Commission. CV coefficient of variation. DE diesel exhaust. DOCs diesel oxidation catalysts. DPF diesel particulate filter. DPM diesel particulate matter. EC elemental carbon. ETS environmental tobacco smoke. Filter Selection Guide Diesel Particulate Filter. Selection Guide for Diesel-powered Equipment in Metal and Nonmetal Mines. First Partial Settlement Agreement 66 FR 35518 (2001) & 66 FR 35521 (2001): basis for July 5, 2001 NPRM. HEI Health Effects Institute. HWE healthy worker effect. MARG Methane Awareness Resource Group. M/NM metal/non-metal. MSHA Mine Safety and Health Administration. NIOSH National Institute for Occupational Safety and Health. NTP National Toxicology Program. OC organic carbon. PAPR powered air-purifying respirator. PEL permissible exposure limit. PPM parts per million. QRA quantitative risk assessment. REA Regulatory Economic Analysis. Second Partial Settlement Agreement 67 FR 47296 (2002): basis for August 14, 2003 NPRM. SD standard deviation. SKC SKC, Inc. TC total carbon. USWA United Steelworkers of America. μg/cm 2 micrograms per square centimeter. μg/m 3 micrograms per cubic meter. 2001 final rule January 19, 2001 DPM final rule. Amended 2001 final rule 2001 final rule amended on February 27, 2002. 2002 final rule February 27, 2002 final rule. 2002 ANPRM Advance Notice of Proposed Rulemaking published on September 25, 2002. 2003 NPRM Notice of Proposed Rulemaking published on August 14, 2003. II. Rulemaking Background On January 19, 2001, MSHA published a final rule (2001 final rule) addressing DPM exposure in underground M/NM mines (66 FR 5706), amended on February 27, 2002 at 67 FR 9180 (2002 final rule). The 2001 final rule established new health standards for underground M/NM mines that use equipment powered by diesel engines. The effective date of the 2001 final 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 2001 final rule in the District of Columbia Circuit Court of Appeals. On February 7, 2001, the Georgia Mining Association, the National Mining Association (NMA), 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 2001 final rule and for postponement of the effective date of the 2001 final rule pending judicial review. The Georgia Mining Association petitioners similarly filed with MSHA a request for an administrative stay or postponement of the effective date of the 2001 final rule. On March 15, 2001, MSHA delayed the effective date of the 2001 final 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 document in the Federal Register delaying the effective date of the 2001 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 the 2001 final rule. A. First Partial DPM 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 2001 final 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 2001 final rule; and included correcting amendments. The second document (66 FR 35521) proposed a rule to clarify § 57.5066(b)(1) and (b)(2) regarding maintenance and to add a new paragraph (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) (2002 final rule), 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 M/NM mines to determine existing concentration levels of DPM; to assess the performance of the SKC, Inc., Eighty Four, PA (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 M/NM underground mining environment before the limits established in the final rule became effective. The final report was issued on January 6, 2003. B. Second Partial Settlement Agreement Settlement negotiations continued on the remaining unresolved issues in the litigation. On July 15, 2002, the parties signed an agreement (second partial settlement agreement) that formed the basis for MSHA's August 14, 2003 proposed rule (68 FR 48668) (2003 NPRM). On July 18, 2002, MSHA published a document in the Federal Register (67 FR 47296) announcing, among other things, that the following provisions of the 2001 final rule would become effective on July 20, 2002: • § 57.5060(a), Addressing the interim concentration limit of 400 micrograms of TC per cubic meter of air; • § 57.5061, Compliance determinations; and • § 57.5071, Environmental monitoring. The document also announced that the following provisions of the rule would continue in effect: • § 57.5065, Fueling practices; • § 57.5066, Maintenance standards; • § 57.5067, Engines; • § 57.5070, Miner training; and • § 57.5075, Diesel particulate records, as they relate to the requirements of the rule that went into effect on July 20, 2002. The document also stayed the effectiveness of the following provisions pending completion of this final rule: • § 57.5060(d), Permitting miners to work in areas where the level of DPM exceeds the applicable concentration limit with advance approval from the Secretary; • § 57.5060(e), Prohibiting the use of personal protective equipment (PPE) to comply with the concentration limits; • § 57.5060(f) Prohibiting the use of administrative controls to comply with the concentration limits; and • § 57.5062, DPM control plan. Finally, the July 18, 2002, document 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 (2002 ANPRM) (67 FR 60199) to amend certain provisions of the 2001 DPM rule. The comment period closed on November 25, 2002. MSHA received comments from underground M/NM mine operators, trade associations, organized labor, public interest groups and individuals. On August 14, 2003, MSHA published the 2003 NPRM in the Federal Register (68 FR 48668) recommending certain revisions to the DPM rule as part of a settlement agreement reached in response to a legal challenge to the DPM standard. Public hearings were held in Salt Lake City, Utah; St. Louis, Missouri; Pittsburgh, Pennsylvania; and Arlington, Virginia in September and October 2003. The comment period closed on October 14, 2003. On February 20, 2004, MSHA published a document in the Federal Register announcing a limited reopening of the comment period on the 2003 NPRM. This document reopened the comment period to obtain public input on three new documents related to the August 14, 2003 rulemaking (69 FR 7881). The three documents were as follows: (1) United States (U.S.) Department of Health and Human Services, Center for Disease Control, National Institute of Occupational Safety and Health, “The Effectiveness of Selected Technologies in Controlling Diesel Emissions in an Underground Mine—Isolated Zone Study at Stillwater Mining Company's Nye Mine,” January 5, 2004. (2) U.S. Department of Labor, Bureau of Labor Statistics, and U.S. Department of Health and Human Services, Center for Disease Control, National Institute of Occupational Safety and Health, “Respirator Usage in Private Sector Firms, 2001,” September, 2003. (3) Chase, Gerald, “Characterizations of Lung Cancer in Cohort Studies and a NIOSH Study on Health Effects of Diesel Exhaust in Miners,” undated, received January 5, 2004. The subsequent comment period closed on April 5, 2004. MSHA received and reviewed written and oral statements on the 2003 NPRM from all segments of the mining community. MSHA informed the mining community in both its 2002 ANPRM and its 2003 NPRM of its intentions to incorporate into the record of the current rulemaking the existing rulemaking record, including the risk assessment to the 2001 final rule. Commenters were encouraged to submit additional evidence of new scientific data related to health risks to underground M/NM miners from exposure to DPM. This final rule for DPM exposure at M/NM mines is based on consideration of the entire rulemaking record, including all written comments and exhibits received related to the 2001 final rule as well as all related data received to the close of this rulemaking record. To serve the interest of the mining community, MSHA is revising §§ 57.5060, 57.5061, 57.5071, and 57.5075 and republishing §§ 57.5065, 57.5066, 57.5067, and 57.5070 of the DPM standards at 30 CFR part 57 in order to present all sections in their entirety in this document. What follows is a discussion of the specific revisions to the 2001 DPM standard: • § 57.5060(a) addressing the interim limit on concentration of DPM. MSHA has changed the 2001 final rule's interim concentration limit of 400 micrograms of TC per cubic meter of air (400 TC μg/m 3 ) to a comparable permissible exposure limit of 308 micrograms of EC per cubic meter of air (308 EC μ/m 3 ); • § 57.5060(c) addressing application and approval requirements for an extension of time in which to reduce the final DPM limit. MSHA has changed the 2001 final rule by requiring MSHA to consider economic feasibility along with technological feasibility factors in weighing whether to grant special extensions; has deleted the limit on the number of special extensions that may be granted to each mine; has limited each extension to a period of one year; has allowed for annual renewals of special extensions; and has allowed the MSHA District Manager, rather than the Secretary, to grant extensions. This final rule retains the scope of the 2001 provision for operators to apply for extensions to the final DPM limit; • § 57.5060(d) addressing certain exceptions to the concentration limits; • § 57.5060(e) prohibiting use of PPE to comply with the concentration limits; • § 57.5060(f) prohibiting use of administrative controls to comply with the concentration limits. MSHA has changed the 2001 final rule by implementing the current hierarchy of controls as adopted in MSHA's other exposure-based health standards for M/NM mines. MSHA's hierarchy includes primacy of engineering and administrative controls to the extent feasible to reduce a miner's exposure to the PEL, but MSHA continues to prohibit rotation of miners for compliance purposes. If a miner's exposure cannot be reduced to the PEL with use of feasible controls, controls are infeasible, or do not produce significant reductions in DPM exposures, the new final rule requires mine operators to supplement a miner's protection with respirators and implement a respiratory protection program. This respiratory protection program must meet the requirements in existing 30 CFR 57.5005, but miners may only use the respirator filters specified by MSHA for DPM in this section. Therefore, MSHA removes the 2001 prohibition against use of respiratory protection without approval by the Secretary and clarifies that use of administrative controls other than rotation of miners is allowed; • § 57.5062, addressing the diesel particulate control plan. This final rule removes the existing requirement for a DPM control plan; and • conforming changes to the following existing standards that were proposed on August 14, 2003: ○ § 57.5061, addressing compliance determinations; ○ § 57.5071, addressing exposure monitoring; and, ○ § 57.5075, addressing recordkeeping requirements. This final rule does not include provisions for written procedures for administrative controls, a written respiratory protection program, medical examination of miners before they are required to wear respiratory protection, and medical transfer of miners who are unable to wear respiratory protection for medical and psychological reasons. III. The Final Concentration Limit In the 2002 ANPRM, 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 2001 final rule. 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. In the 2003 NPRM, MSHA agreed with these commenters and solicited other information from the mining community that would lead to an appropriate final DPM standard. Moreover, MSHA announced its intentions to publish a separate rulemaking to amend the existing final concentration limit in § 57.5060(b). To assist MSHA in achieving this purpose, MSHA requested comments on an appropriate final permissible exposure limit rather than a concentration limit; and asked for information on an appropriate surrogate for measuring miners' DPM exposures. MSHA concluded its request for information by clarifying that revisions to the final DPM concentration limit would not be a part of this rulemaking. In their comments to the 2003 NPRM, organized labor requested that MSHA lower the final DPM limit below 160 micrograms based on feasibility data and the significance of the health risks from exposure to DPM. Industry trade associations and individual mine operators recommended that MSHA repeal the final limit based on issues related to health effects, inability of the mining industry to meet a lower limit than 400 micrograms per cubic meter of air, and the need for MSHA to have the results from the National Institute for Occupational Safety and Health/National Cancer Institute (NIOSH/NCI) study and exposure-response data. MSHA believes that evidence in the current DPM rulemaking record is inadequate for MSHA to make determinations regarding revision to the final DPM limit. IV. The 31-Mine Study A. Summary On January 19, 2001, MSHA published a final standard addressing exposure of underground metal and nonmetal miners to diesel particulate matter (DPM). The standard contained staggered effective dates for interim and final concentration limits. The standard was challenged by industry trade associations and several mining companies, and the United Steelworkers of America (USWA) intervened in the litigation. The parties agreed to resolve their differences through settlement negotiations with MSHA. Thereafter, MSHA delayed the effective date of certain provisions of the standard. As part of the settlement negotiations, MSHA agreed to conduct joint sampling with the litigants at 31 metal and nonmetal underground mines covered by the standard 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. (Executive Summary, Report on the 31-Mine Study) MSHA requested that NIOSH peer review the draft Report on the 31-Mine Study, and NIOSH's conclusions were as follows: 1. Most mines have DPM concentrations higher than 400 TC μg/m 3 . 2. The impactor was effective in eliminating mineral dust from collecting onto the filter analyzed for carbon by NIOSH Method 5040. 3. The ANFO data was inconclusive. 4. Oil mist from the stoper drill is a sub-micron aerosol and a potential interference. Oil mist contamination from the driller can be avoided by sampling upstream of stope or far enough downstream that the oil mist has been diluted enough to give minimal TC concentrations (if this type of sampling is possible). 5. No information about the interference of environmental tobacco smoke is present in this report. 6. The inter-laboratory comparison of the NIOSH method 5040 of paired punches from the same filter showed reasonable agreement between MSHA results and commercial laboratory results and excellent agreement between MSHA and NIOSH laboratory results. (Summary of Findings of this Report in “NIOSH Comments and recommendations on the MSHA DRAFT report: Report on the Joint MSHA/Industry Study: Determination of DPM Levels in Underground Metal and Nonmetal Mines,” dated June 3, 2002) On January 6, 2003, MSHA issued its final report entitled, “MSHA's Report on Data Collected During a Joint MSHA/Industry Study of DPM Levels in Underground Metal And Nonmetal Mines” (Report on the 31-Mine Study). MSHA's 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 * * * (Executive Summary, Report on the 31-Mine Study) MSHA's complete report on the 31-Mine Study is contained in the rulemaking record. MSHA and NIOSH have reviewed the performance characteristics of the SKC sampler, and are satisfied that it accurately measures exposures to DPM. NIOSH found in laboratory and field data that the SKC DPM cassette collected DPM efficiently. In a side protocol of the 31-Mine Study, MSHA tested the efficiency of the SKC DPM cassette to avoid mineral dust in four different mines and did not measure any mineral dust on the filter when the SKC DPM cassette was used. This was confirmed by laboratory results at NIOSH. (Noll, J. D., Timko, R. J., McWilliams, L., Hall, P., Haney, R., “Sampling Results of the Improved SKC Diesel Particulate Matter Cassette,” JOEH, 2005 Jan; 2(1):29-37.) Results of the 31-Mine Study and the MSHA baseline compliance assistance sampling demonstrated that the SKC submicron impactor removed potential interferences from mineral dust from the collected sample. Interference from drill oil mist was found on personal samples collected on the stoper and jackleg 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 an 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. MSHA has found that the use of EC eliminates potential sampling interference from drill oil mist, tobacco smoke, and organic solvents, and that EC consistently represents DPM. In comparison to using TC as the DPM surrogate, using EC would impose fewer restrictions or caveats on sampling strategy (locations and durations), would produce a measurement much less subject to questions, and inherently would be more precise. Furthermore, NIOSH, the scientific literature, and the MSHA laboratory tests indicate that DPM, on average, is approximately 60 to 80% elemental carbon, firmly establishing EC as a valid surrogate for DPM. As part of the 31-Mine Study, representatives from MSHA, NIOSH, and SKC met to address the following issues: • The quality of manufactured SKC DPM cassettes; • The feasibility of adding a dynamic blank filter to the SKC DPM cassette; and • The possibility of putting a number on each SKC DPM cassette. Also, in its October 16, 2001 letter, MSHA informed SKC about the problems that MSHA and the industry encountered using the SKC DPM sampling cassette with the submicron impactor. These problems included: dark flecks, alleged leaks, loose fitting nozzles and connectors, and difficulty in shipping the sampler. As discussed in the report on the 31-Mine Study, SKC was responsive in addressing those concerns. B. Subsequent Activities Some industry commenters continued to state that the sampling and analytical processes for DPM are too new for regulatory use. Other commenters questioned the availability and reliability of the SKC impactor. MSHA moved expeditiously to help resolve the back-order and manufacturing delays for samplers reported in the 31-Mine Study. However, operators who sample alongside MSHA continued to request ample notice to have enough samplers available. MSHA purchased many of the initial production runs of these samplers to conduct its compliance assistance baseline sampling. Once the initial orders were filled, the sampler became more widely available. Some commenters stated that SKC changed the impactor, and that NIOSH should test the new SKC sampler and evaluate its comparability to the model used in the 31-Mine Study. One of these commenters stated that the shelf life of the prior sampler affected TC measurements by adsorbing organic carbon (OC) from the polystyrene assembly onto the filter media and increasing TC measurement. These commenters questioned MSHA's changes to the SKC sampler following completion of the 31-Mine Study, and suggested that a defect to the sampler could have affected the results of the study. 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. Prior to the 31-Mine Study, MSHA had determined the deposit area of the sample filter to be 9.12 square centimeters (cm 2 ) with a standard deviation of 3.1 percent (%). During the initial phases of the sampling analysis of the 31-Mine Study, it became apparent that the variability of the deposit area was greater than originally determined. The filter area is critical to the concentration calculation. The filter area (measured in cm 2 ) is multiplied by the results of the analysis (micrograms per cm 2 ) to get the total filter loading (micrograms). While individual filter areas could be measured, it is more practical to have a uniform deposit area for the calculations. As a result, NIOSH and MSHA consulted with SKC to develop an improved filter cassette design. With the cooperation of MSHA and the technical recommendations and extensive experimental verification by NIOSH, SKC was able to modify their cassette design to produce a consistent and regular DPM deposit area, satisfactorily resolving the problem. SKC, in cooperation with MSHA and NIOSH, then modified the DPM cassette following the 31-Mine Study. The modification was limited to replacing the foil filter capsule with a 32 millimeter (32-mm) ring. This was done to give a more uniform deposit area (8.04 cm 2 ) with negligible variability, and to accommodate two 38-mm quartz fiber filters in tandem (double filters). These double filters are assembled into a single cassette along with the impactor. The 38-mm filters also eliminate cassette leakage around the filters. These modifications were completed and incorporated into units manufactured after November 1, 2002. The results of this project were prepared into a scientific publication, “Sampling Results of the Improved SKC Diesel Particulate Matter Cassette,” referenced above. This paper has been peer reviewed and was published in January 2005. The following abstract was prepared for the study results: Diesel particulate matter (DPM) samples from underground metal/non-metal mines are collected on quartz fiber filters and measured for carbon content using National Institute for Occupational Safety and Health Method 5040. If size selective samplers are not used to collect DPM in the presence of carbonaceous ore dust, both the ore dust and DPM will collect on the quartz filters, causing the carbon attributed to DPM to be artificially high. Because the DPM particle size is much smaller than that of mechanically generated mine dust aerosols, it can be separated from the larger mine dust aerosol by a single stage impactor. The SKC DPM cassette is a single stage impactor designed to collect only DPM aerosols in the presence of carbonaceous mine ore aerosols, which are commonly found in underground nonmetal mines. However, there is limited data on how efficiently the SKC DPM cassette can collect DPM in the presence of ore dust. In this study, we investigated the ability of the SKC DPM cassette to collect DPM while segregating ore dust from the sample. We found that the SKC DPM cassette accurately collected DPM. In the presence of carbon-based ore aerosols having an average concentration of 8 mg/m 3 , no ore dust was detected on SKC DPM cassette filters. We did discover a problem: the surface areas of the DPM deposits on SKC DPM cassettes, manufactured prior to August 2002, were inconsistent. To correct this problem, SKC modified the cassette. The new cassette produced, with 99% confidence, a range of DPM deposit areas between 8.05 and 8.28 cm 2 , a difference of less than 3%. Because the design of the inlet cyclone, impaction nozzles, and the impaction plate and the flow rate did not change, the modifications to the filter assembly did not alter the collection or separation performance of the impactor. Throughout the compliance baseline sampling, the impactor has been a consistent and reliable sampling cassette. Tandem filters were used in the oil mist and ANFO interference evaluations during the 31-Mine Study. The top filter collects the sample and the bottom filter is a dynamic blank. The dynamic blank provides a unique field blank for each DPM cassette. The use of EC as a surrogate would resolve the commenter's concern about shelf life and OC out-gassing on the filter. Shelf life and OC out-gassing are issues relative to OC measurements. These two issues do not apply to an EC measurement. Once the cassettes have been preheated during manufacturing, there is no source, other than sampling, to add EC to the sealed cassette filters. MSHA discussed in the preamble to the 2003 NPRM issues related to interferences, field blanks and the error factor. Some comments on the 2003 NPRM still expressed concerns on interferences and further stated that the MSHA industrial hygiene studies, conducted to verify the magnitude of the interference problem, were not published or peer reviewed and should be removed from the rulemaking record. However, MSHA, organized labor, and the mining industry, through the negotiations process, jointly developed the protocol for conducting the 31-Mine Study. All of the parties agreed on the protocol following numerous discussions among industry, labor, and government experts, and had an opportunity to comment and make changes to the document. Thereafter, MSHA conducted the study, following the agreed upon protocol, and published its results. Before publication, the report was peer reviewed by NIOSH. Industry was given an opportunity to publish their separate results simultaneously with the government. During this rulemaking, industry submitted to MSHA through the notice and comment process their conclusions on the 31-Mine Study in a report titled, “Technical and Economic Feasibility of DPM Regulations.” The industry report is contained in the rulemaking record, and was considered by MSHA in reaching determinations for this final rule. (1) Interferences In response to the question on whether there are interferences when EC is used as the surrogate, some commenters stated that interferences were thoroughly discussed in the preamble to the 2001 final rule, and that reasonable practices to avoid them were stipulated in the rule itself. According to these commenters, this problem should not be revisited in this rulemaking. Other commenters maintained that the 31-Mine Study did not contain the necessary protocols to address all potential interferences. Thus, in their view, MSHA does not have all the data required to answer this question. More specifically, some commenters stated that carbonaceous particulate in host rock has a smaller diameter than the impactor cut point and so, may contaminate EC samples. These commenters then concluded that MSHA should propose additional research and seek comments on the research before concluding that sampling EC with an impactor will eliminate all interference problems. However, no data were presented to support this claim or conclusion. Commenters submitted no new information relative to interferences in response to the 2003 NPRM. (2) Field Blanks A field blank is an unexposed control filter meant to account for background interferences and systematic contamination in the field, spurious effects due to manufacturing and storage of the filter, and systematic analytical errors. The tandem filter arrangement in the sample cassette provides a primary filter for collecting an air sample and a second filter, behind (after) the primary filter, which provides a separate control filter for each sample. This is a much more flexible method of sampling for the mining industry, since it eliminates the need to send a separate control filter to the analytical lab. MSHA informed the public of its intentions to adjust the EC result obtained for each sample by the result obtained for the corresponding media blank when MSHA measures for compliance purposes. When MSHA conducts compliance measurements, MSHA will adjust the result obtained for each corresponding sample by the field blank (tandem filter) result. No comments or information related to field blanks were submitted to MSHA in response to the 2003 NPRM. In its comments on the 2002 ANPRM, NIOSH noted that two types of blanks, media and field, are normally used for quality assurance purposes. A media blank accounts for systematic contamination that may occur during manufacturing or storage. A field blank accounts for possible systematic contamination in the field. NIOSH does not recommend use of field blanks when EC is the surrogate. This is because EC measurements are not subject to sources of contamination in the field that would affect OC and TC results. Quartz-fiber filters are prone to OC vapor contamination in the field and to contamination by less volatile OC (such as oils) during handling. However, such contamination is irrelevant when EC is the surrogate. (3) Error Factor MSHA intends to cite a violation of the DPM EC exposure limit only when MSHA has valid evidence that a violation actually occurred. As with all other measurement-based M/NM compliance determinations, MSHA will issue a citation only if a measurement demonstrates noncompliance with at least 95% confidence. MSHA will achieve this 95% confidence level by comparing each EC measurement to the EC exposure limit multiplied by an appropriate error factor. Generally, an error factor is used to compensate for certain known inaccuracies in the sampling and analytical process, including such things as the reliability of sampling equipment and precision of analytical instrumentation. MSHA will continue to determine that an overexposure has occurred when a sample exceeds the interim limit times the error factor. In this rulemaking, MSHA is discussing the procedure used to obtain the error factor. This procedure is further discussed on the MSHA web site at www.msha.gov under, “Single Source Page for Metal and Nonmetal Diesel Particulate Matter Regulations.” Error factors are based on sampling and analytic errors. The manufacturers of sampling devices thoroughly investigate and quantify the error factors for their devices. While MSHA does not frequently change an error factor, it retains that latitude should significant changes to either analytical or sampling technology occur. The formula for the error factor was based on three factors involved in making an eight-hour equivalent full-shift measurement of EC concentration using NIOSH Method 5040: (1) Variability in air volume ( i.e. , pump performance relative to the nominal airflow of 1.7 L/min); (2) variability of the deposit area of particles on the filter (cm 2 ); and (3) accuracy of the laboratory analysis of EC density within the deposit (μg/cm 2 ). Modifications made to the sampler since the time of the 31-Mine Study have no bearing on the first and third of these factors. Variability of the filter deposit area was represented by a 3.1% coefficient of variation, based on an experiment carried out before the foil filter capsule in the sampling cassette was replaced by a 32-mm ring. Measurements subsequent to introduction of the ring show that variability of the filter deposit area is now less than 3.1% (Noll, J. D., et al , “Sampling Results of the Improved SKC Diesel Particulate Matter Cassette”). This change slightly reduces the error factor stipulated for EC measurements, but not by enough to be of any practical significance. MSHA's error factor model accounts for the joint and related variability in laboratory analysis, and combines that variability with pump flow rate, sample collection size, and other sampling and analytic variables. MSHA was then able to determine the appropriate error factor for EC samples based on a statistically strong database. The analytical method (NIOSH 5040) relies on a punch taken from inside the deposit area on the sample filter. In effect, the punch is a sample of the dust sample. To account for uniformity in the distribution of DPM deposited on the filter, as reflected by different possible locations at which a punch might be extracted, MSHA compared two punches taken from different locations on the same filter to evaluate the accuracy of the analytical method. Therefore, variability between punch results due to their location on the filter is also included in the error factor as calculated by MSHA. Commenters to the 2003 NPRM further questioned whether the NIOSH Method 5040 has been commercially tested. As in the preamble to the 2003 NPRM, MSHA has discussed in detail its findings regarding the NIOSH Method 5040 in this section. NIOSH's peer review of the 31-Mine Study also concludes that the analytical method specified by the diesel standard gives an accurate measure of the TC content of a filter sample. NIOSH confirmed this position by letter of February 8, 2002, in which NIOSH stated that, MSHA is following the procedures of NIOSH Method 5040, based on our review of MSHA P13 (MSHA's protocol for sample analysis by NIOSH Method 5040) and a visit to the MSHA laboratory. V. Compliance Assistance A. Baseline Sampling Summary Under the second partial DPM settlement agreement, MSHA agreed to provide compliance assistance to the M/NM underground mining industry for a one-year period from July 20, 2002 through July 19, 2003. As part of its compliance assistance activities, MSHA agreed to conduct baseline sampling of miners' personal exposures at every underground mine covered by the 2001 final rule. Our baseline sampling began in October 2002 and continued through October 2003. During this period a total of 1,194 valid baseline samples were collected. A total of 183 underground M/NM mines are represented by this analysis. The number of samples per mine range from one to twenty. All 874 valid baseline sampling results in the analysis published in the preamble of the 2003 NPRM are included in this updated analysis. MSHA is including 320 additional valid samples because MSHA decided to continue to conduct baseline sampling after July 19, 2003 in response to mine operators' concerns. MSHA has analyzed all baseline samples, and updated its analysis. Some of these mines were either not in operation or were implementing major changes to ventilation systems during the original baseline period. MSHA is including supplementary samples from seasonal and intermittent mines, mines that were under-represented, and mines that were not represented in the analysis published in the preamble to the 2003 NPRM. Sixty mines included in the former analysis had additional samples taken during the extended assistance period. There are 12 mines in this updated analysis that were not represented in the 2003 analysis. The results of this sampling were used by MSHA in this preamble to estimate current DPM exposure levels in underground M/NM mines using diesel equipment. These sampling results also assist mine operators in developing compliance strategies based on actual exposure levels. This section summarizes analytical results of personal sampling for DPM collected during compliance assistance. There are a total of 1,206 samples. However, 12 samples are invalid due to abnormal sample deposits, broken cassettes or filters, contaminated backup pads, instrument failure 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 or nonmetal 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 with the average number of valid samples per mine ranging from 6.0 to 8.2 (average across all mines is 6.5 samples per mine). The average number of samples per mine classified as “Gold Ore Mining, N.E.C.” increased from an average of 2.0 samples per mine published in the 2003 NPRM preamble to an average of 4.6 samples in this data set. Approximately 79% of all mines sampled during the assistance period have four or more results from DPM sampling in this analysis. Table V-3 lists the number of samples for each category of specific commodity. Average number of samples for more general commodity groups is listed in Table V-2. 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 in the miner's breathing zone and for the miner's full shift regardless of the number of hours worked. For the 1,194 valid personal samples, 85% were collected for at least eight hours. TC and EC levels, as well as DPM levels, are reported in units of micrograms per cubic meter for an 8-hour full shift equivalent. 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 TC content. Each sample was analyzed for organic, elemental, and carbonaceous carbon and calculated TC. Raw analytical results from both laboratories as well as administrative information about the sample were stored electronically in MSHA's Laboratory Information Management System. If a raw carbon result was greater than or equal to 30 μg/cm 2 of EC or 40 μg/cm 2 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 tandem blank was also tested for the same analyses. Otherwise, an unexposed filter from the same manufacturer's lot was used to correct for background levels. In the event the initial TC result was greater than 100 TC μg/cm 2 , a smaller punch of the same exposed filter (in duplicate and with the 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. The equation used to calculate a 480-minute (8-hour) full shift equivalent (FSE) exposure of TC is Total Carbon Concentration = ER06jn05.014 Where: EC = The corrected elemental carbon concentration measured in the thermal/optical carbon analyzer, μg/cm 2 , OC = The corrected organic carbon concentration measured in the thermal/optical carbon analyzer, μg/cm 2 , A = The surface area of the deposit on the filter media used to collect the sample, cm 2 , Flow Rate = Flow rate of the air pump used to collect the sample measured in Liters per minute, and 480 minutes = Standardized eight-hour work shift. All levels of carbon or DPM are reported in 8-hour full shift equivalent TC concentrations measured in μg/m 3 . Because personal sampling was conducted and no attempt was made to avoid interference from cigarette smoke or other OC sources, TC was also calculated using the formula prescribed in the second partial 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. The electronic records of the 1,194 samples 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, 12 samples (1.0%) 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. These samples were subjected to the same laboratory quality assessments as samples collected for compliance purposes. Accordingly, MSHA has included 1,194 samples from miners in the analyses. Table V-2 is a list of the number of valid samples by commodity group. Table V-1.—Reasons for Excluding Samples. Reason for excluding from analysis Metal Stone Trona Other N/M Total Abnormal Sample Deposit 0 1 0 0 1 Cassette/Filter Broken 0 2 0 1 3 Contaminated Backup Pad 1 0 0 0 1 Instrument Failure 1 1 0 0 2 Pump Failed 1 4 0 0 5 Total 3 8 0 1 12 Table V-2.—Number of Mines and Valid Samples, by Commodity Group. Commodity group Number of mines Number of valid samples Average number of valid samples by mine Metal 40 284 7.1 Stone 115 689 6.0 Trona 4 25 6.3 Other N/M 24 196 8.2 Total 183 1,194 6.5 Table V-3 lists the number of samples collected by specific commodities and sorted by average number of samples per mine. Although MSHA made efforts to sample all underground M/NM mines covered by this rulemaking within the specified time frame, several mines have few or no samples for DPM in this analysis. Some M/NM 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 extended its period of baseline sampling especially to incorporate into its analysis those mines with a low sampling frequency or where no samples were collected as of March 26, 2003. Table V-3.—Number of Valid Samples per Mine for Specific Commodities Specific commodity No. of mines No. of samples Average samples per mine Gemstones Mining, N.E.C 2 5 2.5 Dimension Marble Mining 3 9 3.0 Limestone 2 6 3.0 Talc Mining 1 3 3.0 Uranium-Vanadium Ore Mining, N.E.C 1 3 3.0 Gold Ore Mining, N.E.C 19 87 4.6 Construction Sand & Gravel Mining, N.E.C 1 5 5.0 Crushed & Broken Sandstone Mining 1 5 5.0 Hydraulic Cement 1 5 5.0 Lime, N.E.C 4 20 5.0 Copper Ore Mining, N.E.C 2 11 5.5 Dimension Limestone Mining 3 18 6.0 Crushed & Broken Limestone Mining, N.E.C 90 550 6.1 Crushed & Broken Marble Mining 4 25 6.3 Trona Mining 4 25 6.3 Crushed & Broken Stone Mining, N.E.C 4 28 7.0 Gypsum Mining 4 29 7.3 Salt Mining 14 122 8.7 Clay, Ceramic & Refractory Minerals, N.E.C 1 9 9.0 Miscellaneous Metal Ore Mining, N.E.C 1 9 9.0 Lead-Zinc Ore Mining, N.E.C 10 96 9.6 Platinum Group Ore Mining 2 20 10.0 Potash Mining 3 30 10.0 Molybdenum Ore Mining 2 22 11.0 Silver Ore Mining, N.E.C 3 36 12.0 Miscellaneous Nonmetallic Minerals, N.E.C 1 16 16.0 Average of all samples 183 1,194 6.5 There are 63 different occupations in underground M/NM 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 group. Only occupations with 14 or more total samples are listed individually. Occupations with fewer samples were aggregated into a combined group for this table. Table V-4.—Valid Samples, by Occupation and Mine Category. Occupation Metal Stone Trona Other N/M Total Truck Driver 87 152 0 13 252 Front-end Loader Operator 40 149 6 19 214 Blaster, Powder Gang 12 98 0 24 134 Scaling (mechanical) 1 66 0 13 80 Drill Operator, Rotary 3 63 0 9 75 Drill Operator, Jumbo Perc. 10 19 0 9 38 Mechanic 7 15 0 12 34 Complete Load-Haul-Dump 7 2 0 23 32 Utility Man 6 4 15 4 29 Scaling (hand) 4 20 0 2 26 Mucking Mach. Operator 19 1 0 3 23 Roof Bolter, Rock 5 9 0 7 21 Drill Operator, Rotary Air 1 19 0 1 21 Miner, Drift 16 1 0 0 17 Crusher Oper/Worker 0 13 0 2 15 Miner, Stope 14 0 0 0 14 All Others Combined 52 58 4 55 169 Totals 284 689 25 196 1,194 TC levels calculated by EC × 1.3 were lower than TC levels calculated by OC + EC in 858 (72%) of the 1,194 baseline samples. Of the 336 samples where TC = OC + EC was the lower value, 68% 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 6.4% of the paired results did not concur with respect to the 400 TC μg/m 3 standard when measuring TC by the two calculations (OC + EC vs. EC × 1.3). Approximately 19.3% of the samples were above the 400 TC μg/m 3 interim concentration limit when using TC = EC × 1.3 and approximately 22.7% were above the concentration limit when using TC = OC + EC. There is 93.6% concurrence between the two methods of calculating TC and comparing the calculations to the 400 TC μg/m 3 interim concentration limit. Table V-5.—Comparison of Results With 400 TC μg/m 3 Calculating TC by OC + EC or EC × 1.3 All valid samples EC × 1.3 < 400 TC μg/m 3 > 400 TC μg/m 3 Total OC+EC < 400 TC μg/m 3 905 (75.8%) 18 (1.5%) 923 (77.3%) > 400 TC μg/m 3 59 (4.9%) 212 (17.8%) 271 (22.7%) Total 964 (80.7%) 230 (19.3%) 1,194 (100.0%) Table V-6 lists the 26 occupations found to have at least one sample in which the level of TC was over the 400 TC μg/m 3 interim concentration limit (TC = EC × 1.3). Table V-6 is sorted by the median (middle) TC result. The median is reported because it is a more robust measure of the middle value. Changing a single value won't change the median very much. In contrast, the value of the mean can be strongly affected by a single value that is very low or very high. The table also lists the minimum value, maximum 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 TC μg/m 3 (TC = EC× 1.3) Occupation Total samples TC, μg/m 3 Minimum Median Maximum Diamond Drill Operator 1 2,030 2,030 2,030 Ground Control/Timberman 2 368 545 722 Washer Operator 4 353 438 808 Engineer 1 438 438 438 Roof Bolter, Mounted 12 98 335 1,063 Mucking Mach. Operator 23 15 334 872 Miner, Stope 14 100 283 622 Cleanup Man 2 66 283 499 Scoop-Tram Operator 7 14 272 583 Drill Operator, Rotary Air 21 0 240 1,353 Miner, Drift 17 16 228 1,459 Blaster, Powder Gang 134 6 227 1,340 Belt Crew 8 26 225 502 Roof Bolter, Rock 21 63 223 1,310 Truck Driver 252 0 211 1,581 Shuttle Car Operator (diesel) 3 95 201 419 Complete Load-Haul-Dump 32 19 189 824 Drill Operator, Jumbo Perc 38 5 179 1,098 Drill Operator, Rotary 75 3 171 1,109 Motorman 8 59 168 419 Front-end Loader Operator 214 0 158 2,979 Scaling (mechanical) 80 0 139 1,246 Supervisor, Co. Official 13 1 130 856 Utility Man 29 29 94 991 Scaling (hand) 26 18 87 2,013 Mechanic 34 0 84 420 Table V-7 and Chart V-1 provide the percent of overexposures among the four commodity groups. Chart V-2 provides the number of overexposures among the four commodity groups. The metal mines have the highest percent of overexposures followed by stone, then other non-metal mines. For all samples combined, 19.3% were above 400 TC μg/m 3 . Table V-7.—Baseline Samples by Commodity (TC = EC × 1.3) Commodity Number < 400 TC μg/m 3 Number > 400 TC μg/m 3 Total Samples Percent > 400 TC μg/m 3 Metal 195 89 284 31.3 Stone 571 118 689 17.1 Other N/M 174 22 196 11.2 Trona 24 1 25 4.0 All Mines 964 230 1,194 19.3 BILLING CODE 4510-43-U ER06JN05.001 ER06JN05.002 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 68 mines (37%) are in this category. There were no mines with more than 12 samples > 400 TC μg/m 3 for that mine. ER06JN05.003 At four of the mines, all samples taken during the assistance period were above 400 TC μg/m 3 . Between one and ten samples were taken at each of these four mines. No overexposures were found in 115 (63%) of the mines sampled. (See Chart V-4.) BILLING CODE 4510-43-C ER06JN05.004 Tables V-8 and V-9 summarize sample statistics by commodity for TC calculated by TC = EC × 1.3 and TC = EC + OC respectively. Overall, the mean TC as calculated by EC × 1.3 is 255 μg/m 3 . The median level is 174 μg/m 3 . The mean TC level by OC + EC is 293 μg/m 3 and the median level is 226 μg/m 3 . Individual exposure levels of TC vary widely within all commodities and most mines. The commodity groupings reported in Tables V-8 and V-9 were chosen to be consistent with those reported in the 31-Mine Study and the Quantitative Risk Assessment (QRA) for this rule. The mean and median TC values for each group, using EC × 1.3, are lower than the interim compliance limit of 400 μg/m 3 . The mean (median) TC value for metal mines is 356(271) μg/m 3 . The mean (median) for stone mines is 236(149), other non-metal mines is 194(148), and trona mines is 105(82) μg/m 3 . Table V-8 lists additional statistics for TC values compiled by commodity. Table V-8.—Average Levels of TC by Commodity Measured in μg/m 3 (EC × 1.3) [Estimated 8-hour Full Shift Equivalent TC Concentration (μg/m 3 )] TC = EC × 1.3 Metal Stone Other N/M Trona All Mines No. of Samples 284 689 196 25 1,194 Maximum 2,026 2,979 960 407 2,979 Median 271 149 148 82 174 Mean 356 236 194 105 255 Std. Error 19 10 12 16 8 95% CI Upper 392 256 217 138 270 95% CI Lower 319 216 172 73 239 The mean and median TC values for each group of mines as calculated by OC + EC are also lower than the interim compliance limit of 400 μg/m 3 . The mean (median) TC value for metal mines is 370(313) μg/m 3 . The mean for stone mines is 282(209), other non-metal mines is 238(191) and for trona mines is 140(126) μg/m 3 . Table V-9 lists additional statistics for TC values compiled by commodity group. Table V-9.—Average Levels of TC by Commodity Group Measured in μg/m 3 (OC + EC) [Estimated 8-hour Full Shift Equivalent TC Concentration (μg/m 3 )] TC = OC + EC Metal Stone Other N/M Trona All Mines No. of Samples 284 689 196 25 1,194 Maximum 2,045 2,796 1,230 344 2,796 Median 313 209 191 126 226 Mean 370 282 238 140 293 Std. Error 17 11 12 12 8 95% CI Upper 404 303 263 165 308 95% CI Lower 336 261 214 115 278 Tables V-10, V-11, and V-12 show summary statistics for whole DPM exposures for the baseline sampling and the 31-Mine Study. For baseline sampling whole DPM was calculated by EC × 1.3 × 1.25 and by (OC + EC) × 1.25. The 1.25 factor represents the assumption that TC comprises 80% of whole DPM. The other 20% includes the solid aerosols such as ash particulates, metallic abrasion particles, sulfates and silicates. The vast majority of these particulates are in the sub-micron range. Section VI-B discusses the relationship between EC and TC. For whole DPM concentrations, the mean (median) value is 444(339) μg/m 3 for metal mines, 295(186) for stone mines, 243(185) for other non-metal mines, and 132(102) μg/m 3 for trona mines. The whole DPM exposures for Table V-11 were calculated as (OC + EC) × 1.25. Table V-10.—Baseline Whole DPM Concentrations (EC × 1.3 × 1.25, μg/m 3 ), by Mine Category [Estimated 8-hour Full Shift Equivalent Whole DPM Concentration (μg/m 3 )] DPM = EC × 1.3 × 1.25 Metal Stone Other N/M Trona All Mines Number of Samples 284 689 196 25 1,194 Maximum 2,532 3,724 1,200 509 3,724 Median 339 186 185 102 218 Mean 444 295 243 132 318 Std. Error 23 13 15 20 10 95% CI Upper 490 320 272 173 338 95% CI Lower 399 270 214 91 299 Table V-11.—Baseline Whole DPM Concentrations ((EC + OC) × 1.25, μg/m 3 ), by Mine Category [Estimated 8-hour Full Shift Equivalent Whole DPM Concentration (μg/m 3 )] DPM = (EC + OC) × 1.25 Metal Stone Other N/M Trona All Mines Number of Samples 284 689 196 25 1,194 Maximum 2,556 3,495 1,538 430 3,495 Median 392 262 238 158 283 Mean 463 353 298 175 366 Std. Error 21 13 16 15 10 95% CI Upper 505 379 329 206 385 95% CI Lower 421 327 267 144 347 The mean whole DPM concentration for metal and stone mines (as measured by (EC + OC) × 1.25) was significantly lower during baseline compliance assistance sampling than the levels measured during the 31-Mine Study. Table V-12.—31-Mine Study Whole DPM Concentrations (μg/m 3 ) by Mine Category [Estimated 8-hour Full Shift Equivalent Whole DPM Concentration (μg/m 3 )] DPM = (EC + OC) × 1.25 Metal Stone Other N/M Trona Number of Samples 116 105 83 54 Maximum 2,581 1,845 1,210 331 Median 491 331 341 82 Mean 610 466 359 94 Std. Error 45 36 27 9 95% CI Upper 699 537 412 113 95% CI Lower 522 394 306 75 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 the study 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 DPM exposure. Workers inside equipment cabs were not sampled during the 31-Mine Study due to possible interference from cigarette smoke. During baseline compliance assistance sampling, however, personal samples were taken on miners inside cabs. BILLING CODE 4510-43-U ER06JN05.005 MSHA received several comments on the baseline sampling. Some commenters stated that many mines were sampled in a manner that rendered results exceedingly low and not representative of operating conditions. Commenters also stated that the results of independent DPM sampling conducted by operators indicate MSHA's results underestimate DPM exposure. These commenters did not provide data or analyses from mine operators' sampling programs to substantiate their claim. MSHA compliance specialists collected baseline samples in the same manner they have been instructed to use for collecting samples for enforcement purposes. It is expected that personal exposure to DPM will fluctuate due to variations in day to day operations in a mine. Reported levels of DPM are representative of the exposures of the highest risk miners identified during compliance assistance. In an ideal situation, and with unlimited resources, every potentially exposed miner would be individually sampled. It is not necessary or practical, however, to sample all miners on a mine property in order to evaluate personal exposures. Suspected and potential health hazards may be reasonably and adequately evaluated by sampling the maximum risk miner in a work area. The maximum risk miner is the one expected to have the greatest exposure of all of the miners in the area. Other miners in the same work area or area of common exposure sources may reasonably be expected to experience lesser concentrations of occupational hazards than the maximum risk miner. There may be more than one maximum risk miner when activities, operations, and exposure sources vary throughout the day. MSHA acknowledges that some samples were not taken on the highest possible risk occupation at some mines. As previously stated, we continued baseline sampling past the date of July 19, 2003 in response to this concern. A miner experiences high risk because of the location and type of tasks performed relative to the source of the suspected hazard. The miner's predicted environment or duties may change during the course of the work shift. If the working conditions present during the exposure assessment are not typical of the regular mining operation, the sample results may not represent the typical exposure for that occupation. Compliance specialists strive to characterize the higher exposure levels during typical work shifts. The baseline samples are representative of the conditions experienced on work shifts during the defined compliance assistance period. MSHA has obtained the best available information for characterizing recent activities at the relevant M/NM mines. B. DPM Control Technology MSHA participated in a number of compliance assistance activities directed at improving sampling and assisting mine operators with selecting and implementing appropriate DPM control technology. Some of these activities were directed to either a segment of the mining industry, or to the entire industry, while others were conducted on a mine specific basis. In general, activities directed toward a large number of mines included outreach programs, workshops, website postings and publications, while activities directed at an individual mine included evaluation of a specific control technology, and review of the technology in use by or available to a specific mine. Regional DPM Seminars. During September and October, 2002, MSHA conducted regional DPM seminars at the following locations: Ebensburg, PA; Knoxville, TN; Lexington, KY; Des Moines, IA; Kansas City, MO; Albuquerque, NM; Coeur d'Alene, ID; Green River, WY; and Elko, NV. MSHA offered these full-day seminars free of charge in the major underground M/NM 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, a computerized program that calculates DPM concentration reduction. NIOSH Diesel Emission and Control Technologies in Underground M/NM Mines Workshops. MSHA participated in these two workshops in February, 2003 in Cincinnati, OH and March, 2003, in Salt Lake City, UT. The workshops served several purposes. They provided technical presentations and a forum for discussing control technology for reducing exposure to particulate matter and gaseous emissions from the exhaust of diesel-powered vehicles in underground mines. Additionally, they intended to help mine managers, maintenance personnel, safety and health professionals, and ventilation engineers select and apply control technologies in their mines. Speakers, representing MSHA, NIOSH, and several mining companies, provided ample time for questions and in-depth technical discussion of issues raised by participants. National Stone, Sand & Gravel Association (NSSGA)/MSHA DPM Sampling Workshop. This three day seminar, hosted by the Rogers Group, Inc.'s Jefferson County Stone and Underground in Louisville, Kentucky, was held on December 11 through 13, 2002. On the first day, MSHA reviewed DPM sampling procedures, and presented training on pump calibration, sample train assembly and note taking. On the second day, participants traveled to the Rogers Group Jefferson County Mine to conduct full shift sampling on underground miners. Our technical support staff took ventilation measurements and collected area samples to assess DPM emissions in the mine. On the third day, MSHA reviewed engine emission and ventilation measurements. Additionally, MSHA reviewed and discussed DPM outreach material. Approximately 10 industry participants attended the seminar. Nevada Mining Association Safety Committee. In April, 2003, MSHA discussed DPM control technologies at a meeting of the Nevada Mining Association Safety Committee in Elko, NV. Discussion topics included bio-diesel fuel blends, various fuel additives and fuel pre-treatment devices, mine ventilation, environmental cabs, clean engines, and diesel particulate filter (DPF) systems. Mining company representatives discussed their experiences with and perspectives on these technologies. MSHA discussed experiences and observations that it made at various mines, and results of its laboratory and field testing. MSHA South Central Joint Mine Safety and Health Conference. MSHA presented a DPM workshop at this conference in April 2003, in New Orleans, LA. The workshop included a detailed history and explanation of the provisions of the DPM regulation, and a technical presentation on feasible DPM engineering controls. At the April 2004 conference in Albuquerque, NM, MSHA presented a review of DPM control strategies that have generally been adopted in the underground M/NM mining industry. 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). MSHA presented a DPM workshop at this conference in June 2003, in Reno, NV. The workshop included a detailed history and explanation of the provisions of the regulation, and a technical presentation on DPM sampling, analytical tools for identifying and evaluating DPM sources in mines, and feasible DPM engineering controls. DPM Sampling and Control Workshops. In March 2004, MSHA presented full one day workshops in Bloomington, IN and Des Moines, IA. In these workshops, MSHA reviewed the sampling procedures that MSHA inspectors would use for DPM, and MSHA provided hands on instruction to the participants in these procedures. MSHA also presented a review of DPM control strategies that have generally been adopted in the underground M/NM mining industry. Equipment Manufacturers Association (EMA) DPM Workshop. In August 2003, MSHA conducted a DPM workshop for the EMA in Chicago, IL. At this workshop, MSHA reviewed the M/NM DPM regulations, discussed the need for clean engine technology, explained engine emission testing for mines, reviewed the importance of environmental cabs and discussed ventilation issues. Web site. Our Web site, www.msha.gov, contains a single source page for DPM rules for M/NM mines. The page has links to 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 Standard Error Factor for TC Analysis. • MSHA Metal and Nonmetal DPM Standard Compliance Guide of August 5, 2003, addressing the interim DPM limit. • NIOSH Listserver. • MSHA-NIOSH Diesel Particulate Filter Selection Guide for Diesel-powered Equipment in Metal and Nonmetal Mines (Filter Selection Guide), last updated February 20, 2003. • Baseline DPM Sample Results, updated October 2003. • Presentation from Compliance Assistance Workshop, October 16, 2002. • Summary of Requirements: MSHA Standard on Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners that are in effect as of July 20, 2002. • Link to SKC Web site: SKC Diesel Particulate Matter Cassette with Precision-jeweled Impactor. • Diesel Particulate Matter Control Technologies, last updated January 14, 2004. —Table I: Paper/Synthetic Filters. —Table II: Non-Catalyzed Particulate Filters, Base Metal Particulate Filters, Specially Catalyzed Particulate Filters, and High Temperature Disposable Filters. —Table III: Catalyzed (Platinum Based) Diesel Particulate Filters. • Work Place Emissions Control Estimator. • Federal Register documents concerning this and prior DPM rulemakings. • Public comments on this rulemaking. • Economic analyses for this rule and prior DPM rules. • MSHA News Release: MSHA Rules Will Control Miners' Exposure to Diesel Particulate, January 18, 2001. • Program Information Bulletins: —PIB01-10 Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners, August 28, 2001. —PIB02-04 Potential Health Hazard Caused by Platinum-Based Catalyzed Diesel Particulate Matter Exhaust Filters, May 31, 2002. —PIB02-08 Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners-—Summary of Settlement Agreement, August 12, 2002. Additionally, our diesel single source page for the coal industry contains topics that may also be of interest to the M/NM mining industry, particularly for those operations at gassy mines where permissible equipment is required. Specific control technology studies. Following the settlement agreement, MSHA was invited by various mining companies to evaluate the effectiveness of different control technologies for DPM, including ceramic filters, alternative fuels and a fuel oxygenator. Company participation was essential to the success of each test. MSHA evaluated ceramic filters in two mines, one where MSHA was the only investigator and one where NIOSH was the primary investigator. In our test, MSHA evaluated DPM on a production unit 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. MSHA evaluated bio-diesel fuel in two mines. In one, MSHA evaluated a 20% and a 50% recycled bio-diesel fuel and a 50% new bio-diesel. In the other, MSHA evaluated a 35% recycled bio-diesel fuel and a 35% new bio-diesel. MSHA evaluated the fuel catalyst system in one mine. MSHA sampled the mine exhaust with fuel catalyst systems installed on all production equipment, and also without the units installed. MSHA evaluated water emulsion diesel fuel in four mines. Following is a summary of the individual mine technology evaluation studies: Kennecott Greens Creek Mining Company: MSHA participated with Kennecott Greens Creek Mining Company in a collaborative test to verify the efficiency of catalyzed ceramic DPFs for reducing diesel particulate emissions. The goal of the testing was to identify 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. MSHA also determined relative engine gaseous and DPM emissions for the equipment under specific load conditions. MSHA conducted the tests over a two-week period. MSHA sampled three shifts with ceramic after-filters installed; and three shifts without the after-filters. MSHA also collected personal samples to assess worker exposures, and area samples to assess engine emissions. MSHA took both gaseous and diesel particulate measurements. 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 DPFs may have a significant impact on personal exposures. The following findings and conclusions were obtained from the test: 1. The results of the raw exhaust gas measurements conducted during the test indicate that the engines were operating properly. 2. The ceramic filters installed on the machines used in this test do not adversely affect 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% when after-filters were used. 5. CO levels decreased by up to one-half while the catalyzed filters were used. There appeared to be an increase in NO 2 (Nitrous Dioxide) while catalyzed filters were being used; however, it is 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 exposure by 75% when DPFs were in use and by 80% when DPFs 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 DPFs reduced average engine DPM emissions by 96%. 9. The reduction in personal exposure was not attributed solely to DPF 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 our compliance assistance program, MSHA provided support to mining operations to evaluate diesel particulate control technologies. The test was initiated by the industry partner, and, along with NIOSH, MSHA provided support for test design, data collection, and sample and data analysis. The project was funded by Carmeuse and Kentucky Department of Energy, through the Kentucky Clean Fuels Coalition. The initial test was conducted in two phases, using a 20% and a 50% bio-diesel blend of recycled vegetable oil (RVO), each mixed with 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 test, 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 TC and EC 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 TC. Results for the 20% and 50% RVO indicated 33% and 69% reductions in DPM emissions, respectively. Results for the tests on the 50% blend of new soy bio-diesel fuel, showed about a 37% reduction in DPM emissions. Carmeuse North America, Inc., Black River Mine: Following the success of the bio-diesel tests at Maysville Mine, Carmeuse requested our assistance in continuing the bio-diesel optimization testing at their Black River Mine. Two bio-diesel blends were tested, and a baseline test was made. In each test personal exposures and the mine exhaust were tested for two shifts. The two bio-diesel blends included a 35% RVO and a 35% blend of new soy oil. Results for the 35% RVO showed a 32% reduction in DPM emissions. Results of the 35% blend of new soy bio-diesel fuel showed an approximate 16% reduction in DPM emissions. Stone Creek Brick Company, Water Emulsion Fuel Tests: During the Stone Creek Brick Company compliance assistance visit, MSHA identified several control strategies that would reduce DPM emissions and exposures. These strategies included: The installation of clean engines, the use of alternative fuels, and an increase in mine ventilation. The mine chose to implement alternative fuel use followed by an engine replacement program. MSHA provided in-mine testing to evaluate the impact of using an alternative fuel. The company chose to use a water emulsion fuel. This fuel is an EPA approved fuel, consisting of a 20% blend of water with No. 2 diesel fuel. A surfactant is added to keep the water and diesel fuel from separating. MSHA sampled at the mine before (using No. 2 diesel fuel) and after the implementation of the fuel. MSHA collected personal samples to evaluate the worker exposure and area samples to evaluate emissions. Results of the testing showed that the highest exposure was reduced from 823 TC μg/m 3 to 321 TC μg/m 3 (61% reduction). EC emissions were reduced by 49% and TC emissions were reduced by 3%. The lack of a reduction in TC emissions was attributed to the lower combustion temperature resulting from the water emulsion fuel and the older engine technology in use. The older engines have larger injector nozzles which do not provide efficient fuel burning. The mine has been using the fuel for approximately one year, and continues to be satisfied with the results. Carmeuse North American, Inc., Maysville Mine, Water Emulsion Fuel Tests: MSHA provided assistance to Carmeuse North American, Inc., to evaluate summer and winter blends of a water emulsion fuel at their Maysville Mine. For the first test, emission reductions for a 10% blend (winter blend) of water with No. 2 diesel fuel was compared to a 35% blend of RVO. Emission reductions were compared to both a 35% blend of RVO and standard No. 2 diesel fuel. MSHA collected personal samples to evaluate the worker exposure and area samples to evaluate emissions. Results of the testing showed that the highest average exposure (high scaler working outside a cab) was reduced from 254 TC μg/m 3 to 145 TC μg/m 3 (43% reduction) when changing from RVO to the water emulsion. EC emissions were reduced by 52% and TC emissions were reduced by 49% for the water emulsion to 35% RVO fuel comparison. EC emissions were reduced by 77% and TC emissions were reduced by 74% for the water emulsion to standard diesel fuel comparison. For the second test, emission reductions for a 20% blend (summer blend) of water with No. 2 diesel fuel was compared to a 35% blend of RVO. Emission reductions were compared to both a 35% blend of RVO and standard No. 2 diesel fuel. The comparison to No. 2 diesel fuel was obtained by combining the water emulsion to the 35% RVO results and previously obtained 35% RVO to No. 2 diesel fuel results. MSHA collected personal samples to evaluate the worker exposure and area samples to evaluate emissions. For the summer blend, EC emissions were reduced by 60% and TC emissions were reduced by 59% for the water emulsion to 35% RVO fuel comparison. EC emissions were reduced by 81% and TC emissions were reduced by 79% for the water emulsion to standard diesel fuel comparison. Carmeuse North American, Inc., Black River Mine, Water Emulsion Fuel Tests: MSHA provided assistance to Carmeuse North American, Inc. to evaluate summer and winter blends of a water emulsion fuel at their Black River Mine. For these tests, emission reductions for 10% and 20% blends (winter blend) of water with No. 2 diesel fuel was compared to a 35% blend of RVO. Emission reductions were compared to both a 35% blend of RVO and standard No. 2 diesel fuel. MSHA collected personal samples to evaluate the worker exposure and area samples to evaluate emissions. For the winter blend (10%), EC emissions were reduced by 46% and TC emissions were reduced by 45% for the water emulsion to 35% RVO fuel comparison. EC emissions were reduced by 63% and TC emissions were reduced by 62%, for the water emulsion to standard No. 2 diesel fuel comparison. For the summer blend (20%), EC emissions were reduced by 61% and TC emissions were reduced by 54% for the water emulsion to 35% RVO fuel comparison. EC emissions were reduced by 73% and TC emissions were reduced by 68% for the water emulsion to standard diesel fuel comparison. Martin Marietta, Durham Mine, Water Emulsion Fuel Tests: MSHA provided assistance to Martin Marietta to evaluate a summer blend of water emulsion fuel at their Durham Mine. This was a multi-level mine, with a 15% ramp between levels. For this test, emissions for a 20% blend of water with No. 2 diesel fuel was compared to standard No. 2 diesel fuel. MSHA collected personal samples to evaluate the worker exposure and area samples to evaluate emissions. Even with the 15% ramps, the loss in horsepower due to the fuel did not adversely effect the mine operations. Results of the testing showed that the highest average exposure (powder crew working outside a cab) was reduced from 372 TC μg/m 3 to 54 TC μg/m 3 (85% reduction) when changing from No. 2 diesel fuel to the water emulsion. EC emissions were reduced by approximately 80% for the water emulsion compared to standard diesel. Rogers Group, Jefferson County Mine: MSHA was invited to this mine to evaluate a fuel catalyst system that was installed in the fuel line of the diesel equipment. The company had installed the units to increase fuel economy, and sought to determine the effects of the units on DPM. Prior to the units having been installed, MSHA had conducted baseline sampling and had collected personal samples on production workers and area samples in the mine exhaust airflow. After the units were installed on loaders and trucks and the units had accumulated 100 hours of operation, sampling was repeated. Results indicated that the use of the fuel catalyst had no measurable effect on either DPM exposure or emissions. Summary of DPM control technology: In addition to conducting baseline sampling and providing assistance in developing DPM control strategies at specific mines, MSHA assessed the effectiveness of various DPM controls during and following the compliance assistance period. These controls included alternative fuels, fuel oxygenators, environmental cabs and ceramic DPFs. Alternative fuels evaluated included various blends of bio-diesel fuels (including both Virgin Soy Oil (VSO) and RVO), No. 1 diesel fuel, and water emulsion fuels. The resulting reduction in DPM emissions for each of these controls is given in Chart V-6. All reductions are compared to diesel emissions with low sulfur No. 2 diesel fuel. All bio-diesel tests were conducted at mines with relatively clean engines. The first water emulsion test was conducted at a mine utilizing older engines. Subsequent water emulsion tests were conducted at mines utilizing clean engines with oxidation catalytic converters. BILLING CODE 4510-43-U ER06JN05.006 BILLING CODE 4510-43-C Assistance for Developing Control Strategies Martin Marietta Aggregates: MSHA provided compliance assistance during full-day visits at the North Indianapolis Mine and the Parkville Mine in March, 2003, and at the Kaskaskia Mine and the Manheim Mine in May, 2003. MSHA reviewed each mine's DPM sampling history, current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. MSHA discussed the full range of engineering controls, demonstrated an exhaust temperature measurement and data logging system, and presented a spreadsheet for using such data to select appropriate filter systems. MSHA presented a simple approach for measuring the effectiveness of cab air filtering and pressurization systems, identified the highest DPM-emitting equipment (so future equipment-specific DPM control efforts could be appropriately focused), and discussed the likely effect of various ventilation system upgrades. Rogers Group, Oldham County Mine: MSHA provided compliance assistance at this mine during a full-day visit in November 2002. MSHA conducted extensive DPM sampling at the mine, collecting both personal exposure samples and area samples. Further, MSHA collected DPM samples from both inside and outside of equipment cabs. No personal samples exceeded 160 TC μg/m 3 . MSHA reviewed current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. MSHA discussed the full range of engineering controls. Results from this survey indicate the environmental cabs significantly reduced the DPM exposure of equipment operators. Rogers Group, Jefferson County Mine: MSHA provided compliance assistance at this mine during a full-day visit in December 2002. MSHA collected both personal exposure samples and area samples. The highest personal sample, collected on the loader, was 468 TC μg/m 3 . This loader was operated with the window open. MSHA reviewed current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. Mechanical ventilation was provided for the mine. MSHA discussed the full range of engineering controls, demonstrated an exhaust temperature measurement and data logging system, and presented a spreadsheet for using such data to select appropriate filter systems. MSHA presented a simple approach for measuring the effectiveness of cab air filtering and pressurization systems, identified the highest DPM-emitting equipment (so future equipment-specific control efforts could be appropriately focused), and discussed the likely effect of various ventilation system upgrades. Nalley and Gibson, Georgetown Mine: MSHA provided compliance assistance at this mine during a full-day visit in May 2003. MSHA reviewed current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. MSHA collected DPM samples to assess improvements since the baseline sampling. At that time, mechanical ventilation provided airflow to the mine. MSHA discussed the full range of engineering controls, demonstrated an exhaust temperature measurement and data logging system, and presented a spreadsheet for using such data to select appropriate filter systems. MSHA presented a simple approach for measuring the effectiveness of cab air filtering and pressurization systems, identified the highest DPM-emitting equipment (so future equipment-specific DPM control efforts could be appropriately focused), and discussed the likely effect of various ventilation system upgrades. Stone Creek Brick Company: MSHA provided compliance assistance at this mine during a full-day visit in May 2003. MSHA reviewed current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. MSHA collected DPM samples from underground miners. The mine was using mechanical ventilation. None of the equipment had environmental cabs. MSHA discussed the full range of engineering controls, presented a spreadsheet for using such data to select appropriate filter systems, identified the highest DPM-emitting equipment (so future equipment-specific DPM control efforts could be appropriately focused), and discussed the likely effect of various ventilation system upgrades. Wisconsin Industrial Sand Co., Maiden Rock Mine: MSHA provided compliance assistance at this mine during a full-day visit in May 2003. MSHA reviewed the mine's current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. MSHA discussed the full range of engineering controls, presented a spreadsheet for using such data to select appropriate filter systems, and identified the highest DPM-emitting equipment so future equipment-specific DPM control efforts could be appropriately focused. Gouverneur Talc Company, Inc., No. 4 Mine: MSHA provided compliance assistance at this mine during a full-day visit in May 2003. DPM samples were collected on underground workers. MSHA reviewed then current operating and equipment maintenance practices, ventilation, diesel equipment inventory, and steps taken to date and future plans to reduce DPM exposures. MSHA discussed the full range of engineering controls, demonstrated an exhaust temperature measurement and data logging system, and presented a spreadsheet for using such data to select appropriate filter systems. MSHA presented a simple approach for measuring the effectiveness of cab air filtering and pressurization systems, identified the highest DPM-emitting equipment (so future equipment-specific control efforts could be appropriately focused), and discussed the likely effect of various ventilation system upgrades. Additional specific mine compliance assistance: Following the initial baseline sampling period, MSHA compiled a list of mines having at least one DPM sample which exceeded the 400 TC μg/m 3 limit. Of the 183 mines sampled, approximately 69 mines had at least one sample over the 400 TC μg/m 3 interim TC limit. Of the 69 mines with one or more overexposures, 44 used room and pillar mining methods. These include stone mines, salt mines and a potash mine. Of the 44 room and pillar mines, MSHA provided specific compliance assistance to 36 of these mines (two mines were closed and two mines declined assistance). Although trona mines use room and pillar mining methods, they were not visited because they were in compliance with the 400 TC μg/m 3 limit. The remaining 15 mines with overexposures were multilevel metal mines using a variety of stoping mining methods. Industry seminars were provided to assist these mines. Typically, the high risk workers in the mines visited were the face workers that worked outside an environmental cab. Production loader and truck operators had elevated exposures when they either did not have an environmental cab or when the cab was not being properly maintained. Additional high risk workers include the blasting crew, drillers, and roof bolters. During each mine visit, DPM samples were collected unless the mine had been recently sampled or the mine reported no additional DPM controls had been implemented since MSHA's previous sampling was conducted. The DPM controls, including engines, ventilation, cabs, fuels and work practices, were reviewed with mine management. Specific engine emission rates, mine ventilation rates, cab pressures and work practices were determined. At some mines, a temperature trace of an engine exhaust was made. The information was entered into a computer spreadsheet model to assess the effect of control changes on DPM levels and to assist the mine in developing a DPM control strategy. Laboratory Compliance Assistance: In addition to the compliance assistance field tests, our 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 M/NM or coal mines. Evaluating paper/synthetic media as exhaust filters: MSHA has evaluated paper/synthetic media as exhaust filters. These filters have shown DPM removal efficiencies in excess of 90% in the laboratory when tested on our test engine using the test specified in subpart E of part 7. The laboratory has tested approximately 20 different paper/synthetic media from 10 different filter manufacturers. Although 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 M/NM 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. The 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 equipment in M/NM mines, particularly gassy mines where permissible equipment is required. Evaluating Ceramic Filter Systems: MSHA worked with six ceramic filter manufacturers to evaluate the effects of their catalytic wash-coats on NO 2 production. As discussed under the “Effectiveness of the DPM Estimator” portion of this preamble, catalytic wash-coats on the ceramic filters may cause increases in NO 2 levels. MSHA used our test engine (Caterpillar 3306 PCNA) and followed the test procedures in subpart E of 30 CFR part 7. The DPM single source webpage lists the ceramic filters that have significantly increased NO 2 levels, as well as the ceramic filters that are not known to increase NO 2 levels. MSHA tested the DPM removal efficiencies of these filters during the laboratory tests. The efficiency results agree with the efficiencies posted on our web site DPM Control Technologies with Percent Removal Efficiency page (85% for cordierite and 87% for silicon carbide). Finally, MSHA 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 at up to 99% efficiency. Evaluation of Fuel Oxygenator System: MSHA'S laboratory completed tests on the Rentar TM in-line fuel catalyst. The Rentar TM unit was installed on a Caterpillar TM 3306 ATAAC, which was coupled to a generator. MSHA used an electrical load bank to load the engine under various operating conditions. To establish a baseline, MSHA tested the engine for gaseous and DPM emissions without the Rentar TM unit. The unit was then installed, and MSHA operated the engine for a 100 hour break-in period. MSHA then repeated the gaseous and DPM emission measurements. The test results of the one laboratory evaluation for this control device to date showed no significant reductions in whole diesel particulate, however, the data did not show any adverse effects on the raw whole DPM exhaust emission. NIOSH's results were consistent with MSHA's results, and showed no significant EC reductions and no adverse effects on the engine's emissions. MSHA has discussed with Rentar TM further laboratory tests. Evaluation of a Magnet System: MSHA performed laboratory tests for Ecomax, a manufacturer of a magnet system installed on the fuel line, oil filter, air intake and radiator. MSHA performed a preliminary field test of this product at a surface aggregate operation. The magnetic device demonstrated a 30% reduction in CO levels. The laboratory tests were performed with the Ecomax system installed and compared to our baseline engine data. The test results of the one laboratory evaluation for this control device to date showed no significant reductions in whole diesel particulate, however, the data did not show any adverse effects on the raw DPM exhaust emissions. Evaluation of the Fuel Preporator ® System: MSHA's laboratory tested a fuel preparator system. The system is designed to remove collected air from the fuel system for better fuel combustion. The results of the system installed were compared to the baseline engine. The test results of the one laboratory evaluation for this control device to date showed no significant reductions in whole diesel particulate, however, the data did not show any adverse effects on the raw DPM exhaust emissions. NIOSH also conducted tests in our lab on the Fuel Preporator ® and the results were consistent with MSHA's results. There were no significant EC reductions and no adverse effects on the engine's emissions. VI. DPM Exposures and Risk Assessment A. Introduction In support of the 2001 final rule, MSHA published a comprehensive risk assessment (66 FR at 5752-5855, with corrections at 35518-35520). In the following discussion, we will refer to the risk assessment published in conjunction with the 2001 final rule as the “2001 risk assessment.” The 2001 risk assessment presented MSHA's evaluation of health risks associated with DPM exposure levels encountered in the mining industry. This was based on a review of the scientific literature available through March 31, 2000, along with consideration of all material submitted during the applicable public comment periods. The 2001 risk assessment was divided into three main sections. Section 1 (66 FR at 5753-5764) contained a discussion of U.S. miner exposures based on field data collected through mid-1998. An important conclusion of this section was that, prior to the 2001 final rule, * * * median dpm concentrations observed in some underground mines are up to 200 times as high as mean environmental exposures in the most heavily polluted urban areas [footnote deleted] and up to 10 times as high as median exposures estimated for the most heavily exposed workers in other occupational groups. [66 FR at 5764] Section 2 of the 2001 risk assessment (66 FR at 5764-5822) reviewed the available scientific literature on health effects associated with DPM exposures. This review covered effects of both acute and chronic exposures and also contained a discussion of potential mechanisms of toxicity. The review of acute effects included anecdotal reports of symptoms experienced by exposed miners, studies based on exposures to diesel emissions, and studies based on exposures to particulate matter in the ambient air. The review of chronic effects included studies based specifically on exposures to diesel emissions and studies based more generally on exposures to fine particulate matter in the ambient air. As part of this discussion, MSHA evaluated 47 epidemiologic studies examining the prevalence of lung cancer within groups of workers occupationally exposed to DPM and discussed the criteria used to evaluate and rank these studies (66 FR at 5774-5810). For both acute and chronic health effects, information from genotoxicity studies and studies on laboratory animals was discussed in the separate subsection on mechanisms of toxicity. Section 2 of the 2001 risk assessment also explained MSHA's rationale for utilizing certain types of information whose relevance had been questioned during the public comment periods: health effects observed in animals, health effects that are reversible, and health effects associated with fine particulate matter in the ambient air (66 FR at 5765-55767). In section 3 of the 2001 risk assessment (66 FR at 5822-5855), MSHA evaluated the best available evidence to ascertain whether exposure levels currently existing in mines warranted regulatory action pursuant to the Mine Act. To do this, MSHA addressed three questions: (a) Whether health effects associated with occupational DPM exposures constitute a “material impairment” to miner health or functional capacity; (b) whether exposed miners were at significant excess risk of incurring any of these material impairments; and (c) whether the 2001 final rule would substantially reduce such risks. After careful consideration of all the submitted public comments, the 2001 risk assessment established three main conclusions: 1. Exposure to dpm can materially impair miner health or functional capacity. These material impairments include acute sensory irritations and respiratory symptoms (including allergenic responses); premature death from cardiovascular, cardiopulmonary, or respiratory causes; and lung cancer. 2. At dpm levels currently observed in underground mines, many miners are presently at significant risk of incurring these material impairments due to their occupational exposures to dpm over a working lifetime. 3. By reducing dpm concentrations in underground mines, the rule will substantially reduce the risks of material impairment faced by underground miners exposed to dpm at current levels. The third of these conclusions was supported primarily by a quantitative risk assessment for lung cancer (66 FR at 5848-5854). Throughout the current rulemaking, MSHA advised the mining community of its intent to include the 2001 risk assessment in the current rulemaking record to support this final rule. In this preamble, MSHA supplements the 2001 risk assessment with new exposure data and health effects literature published after March 31, 2000. MSHA asked that public comment be focused on this supplemental information. Nevertheless, some commenters presented critiques challenging the 2001 risk assessment and disputing scientific support for any DPM exposure limit, especially by means of an EC surrogate. Other commenters endorsed the 2001 risk assessment and stated that recent scientific publications support MSHA's conclusions. MSHA also received a number of comments from the mining industry suggesting that the risk assessment lacks an adequate scientific foundation and does not comply with present requirements under OMB and information quality guidelines to use the best available, peer reviewed science. The risk assessment sustaining this final rule uses the best available, peer-reviewed scientific studies. It supplements the risk assessment sustaining the 2001 final rule and the existing coal DPM final rule also promulgated on January 19, 2001 (66 FR 5526) (coal rule). The coal rule was unchallenged by the mining community. Before promulgating the 2001 final rule, MSHA provided a copy of its draft risk assessment supporting the 2001 rule for peer review to two experts in the field of epidemiology and risk assessment. These experts evaluated the overall methodology used by MSHA in the draft risk assessment, the appropriateness of the studies selected by MSHA, and MSHA's conclusions. MSHA had the draft independently peer-reviewed, published the evidence and tentative conclusions for public comment, and incorporated the reviewers' recommendations in the final version. In the 2001 risk assessment, MSHA carefully laid out the best available evidence, including shortcomings inherent in that evidence. Of particular note is that the two quantitative meta-analyses of lung cancer studies supporting the 2001 risk assessment were peer reviewed and published in scientific journals. (Bhatia, Rajiv, et al. , “Diesel Exhaust Exposure and Lung Cancer,” Journal of Epidemiology, 9:84-91, January 1998, and Lipsett M., and Campleman, Susan, “Occupational Exposure to Diesel Exhaust and Lung Cancer: A Meta-Analysis,” American Journal of Public Health, (89) 1009-1017, July 1999). MSHA informed the public as early as September 25, 2002, in the 2002 ANPRM for this final rule, and again in the 2003 NPRM, that MSHA would incorporate the existing rulemaking record, including the 2001 risk assessment, into the record of this rulemaking. MSHA was open to considering any new scientific evidence relating to its risk assessment. Commenters were encouraged in the instant rulemaking to submit additional evidence of new scientific information related to health risks associated with exposure to DPM. After considering both the more recent scientific literature and all of the submitted comments, MSHA has concluded that no change is warranted in the 2001 risk assessment's conclusions with respect to health risks associated with DPM exposures. Section VI.B updates Section 1 of the 2001 risk assessment by summarizing the new exposure data that became available after publication of the 2001 final rule. This summary includes a description of the relationship between EC and TC observed in these exposure measurements, and addresses public comments on possible health implications of substituting EC for TC as a surrogate measure of DPM. In Section VI.C, MSHA reviews some of the more recent scientific literature (April 2000-March 2003) pertaining to adverse health effects of DPM and fine particulates in general. In addition, this section updates the 2001 risk assessment's discussion of scientific evidence on mechanisms of DPM toxicity. Thus, Section VI.C supplements Section 2 of the 2001 risk assessment. Section VI.C also discusses a document by Dr. Gerald Chase that purports to analyze preliminary data extracted from an ongoing NIOSH/NCI study. Finally, in Section VI.D, MSHA assesses current risk to underground M/NM miners in light of the most recent exposure and health effects information. Section VI.D also responds to a critique of the 2001 risk assessment submitted by Dr. Jonathan Borak on behalf of the MARG Diesel Coalition (MARG) and the NMA. B. DPM Exposures in Underground M/NM Mines In Section 1 of the 2001 risk assessment, MSHA evaluated exposures based on 355 samples collected at 27 underground U.S. M/NM mines prior to promulgating the 2001 rule. Mean DPM concentrations found in the production areas and haulageways at those mines ranged from about 285 μg/m 3 to about 2000 μg/m 3 , with some individual measurements exceeding 3500 μg/m 3 . The overall mean DPM concentration was 808 μg/m 3 . All of the samples considered in the 2001 risk assessment were collected prior to 1999, and some were collected as long ago as 1989. Two new bodies of DPM exposure data, collected after promulgation of the 2001 final rule, have now been compiled for underground M/NM mines: (1) Data collected in 2001 and 2002 from 31 mines for purposes of the 31-Mine Study and (2) data collected between 10/30/2002 and 10/29/2003 from 183 mines to establish a baseline for future samples. Key results from these two datasets are summarized in the next two subsections below. Following these summaries, the relationship between EC and TC, including the ratio of EC to TC (EC:TC) is discussed. This discussion is based exclusively 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. The subsection concludes with a response to comments on the potential health effects of substituting EC for TC as a surrogate measure of DPM. It should be noted that the new exposure data reflect conditions at least two years, and up to five years, later than the most recent miners' exposure data considered in the 2001 risk assessment. Furthermore, all of the new exposure data were obtained after promulgation of the 2001 rule. It is, therefore, reasonable to expect that the data discussed below would show generally different exposure levels than those presented in the 2001 risk assessment—both on account of normal technological changes over time and because of DPM controls that may have been implemented in response to the 2001 rule. (1) Data from 31-Mine Study MSHA collected 464 DPM samples in 2001 and 2002 at 31 underground M/NM mines. (For a more detailed description, see MSHA's final report on the 31-Mine Study.) Of these 464 samples, 106 were voided—mostly because of potential interference by sources of OC other than DPM. 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 Avg. number of valid samples per mine Metal 11 116 10.5 Stone 9 105 11.7 Trona 3 54 18.0 Other 7 83 11.9 Total 30 358 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% of all DPM. The mean concentration across all 358 valid samples was 432 μg/m 3 (Std. error = 21.0 μg/m 3 ). The mean concentration was greatest at metal mines, followed by stone and “other.” 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 (μ/m 3 ), By Mine Category [DPM Is Estimated by TC ÷ 0.8] Metal Stone Trona Other No. of samples 116 105 54 83 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. 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 mines were not statistically significant. 1 For the 304 valid samples taken at mines other than trona, the mean DPM concentration was 492 μg/m 3 (Std. error = 23.0 μg/m 3 ). 1 These conclusions derive from an analysis of variance, based on TC measurements, described in the Report on 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% of DPM, the mean DPM concentration observed was 1019 μg/m 3 at the single mine exhibiting greatest DPM levels. Four of the nine valid samples at this mine exceeded 1487 μg/m 3 . In contrast, DPM concentrations never exceeded 500 μg/m 3 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 others). (Note that 500 μg/m 3 is the whole particulate equivalent of the 400 TC μg/m 3 interim limit.) Some individual measurements exceeded 200 DPM μg/m 3 at all but one of the mines sampled. (2) Baseline Data MSHA s baseline sampling results are presented in Section III, Compliance Assistance. These results provide the basis for the present discussion. The baseline samples discussed here, in connection with the risk assessment, were collected and analyzed between October 30, 2002 and October 29, 2003. They comprise a total of 1,194 valid samples collected from 183 mines. MSHA is including 320 additional valid samples because MSHA decided to continue to conduct baseline sampling after July 19, 2003 in response to mine operator's concerns. Some of these mines were either not in operation or were implementing major changes to ventilation systems during the original baseline period. MSHA is including supplementary samples from seasonal and intermittent mines, mines that were under-represented, and mines that were not represented in the analysis published in the proposed preamble in 2003. Table VI-3 summarizes, by general commodity, the EC levels measured during MSHA's baseline sampling through October 29, 2003. The overall mean eight-hour full shift equivalent EC concentration was 196 μg/m 3 , and the overall median was 134 μg/m 3 . Table VI-4 provides a similar summary for estimated DPM levels, using DPM ≉ TC/0.8 and TC ≉ 1.3 × EC. 2 Under these assumptions, the estimated mean DPM level was 318 μg/m 3 , and the median was 218 μg/m 3 . 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-3 and VI-4 present overall results both including and excluding the three underground trona mines sampled. 3 2 The relationship DPM ≉ TC/0.8 is the same as that assumed in the 2001 risk assessment. The relationship TC 1.3 × EC was formulated under the settlement agreement, based on TC:EC ratios observed in the joint 31-Mine Study, as described in the subsection VI.3 of this preamble. 3 The distributions of EC values are skewed. Therefore, the standard errors and confidence intervals reported in Tables VI-3 and VI-4 should be interpreted with caution. Table VI-3.—Baseline EC Concentrations 8-hour Full Shift Equivalent EC Concentration (μg/m 3 ) Metal Stone Other N/M Trona Total Total excluding Trona No. of Samples 284 689 196 25 1,194 1,169 Maximum 1,558 2,291 738 313 2,291 2,291 Median 208 115 114 63 134 137 Mean 273 181 150 81 196 198 Std. Error 14 8 9 12 6 6 95% UCL 302 197 167 106 208 210 95% LCL 245 166 132 56 184 186 Table VI-4.—Baseline DPM Concentrations [DPM is estimated by (1.3 × EC) ÷ 0.8] Estimated 8-hour Full Shift Equivalent DPM Concentration (μg/m 3 ) Metal Stone Other N/M Trona Total Total excluding Trona No. of Samples 284 689 196 25 1,194 1,169 Maximum 2,532 3,724 1,200 509 3,724 3,724 Median 339 186 185 102 218 223 Mean 444 295 243 132 318 322 Std. Error 23 13 15 20 10 10 95% UCL 490 320 272 173 338 342 95% LCL 399 270 214 91 299 303 Baseline EC sample results varied widely between mines within commodities and also within most mines. Table VI-5 summarizes baseline EC results for the 26 occupations found to have at least one sample where the EC level exceeded the 308 μg/m 3 8-hour full shift equivalent interim EC limit. As indicated by the table, EC levels varied widely within each occupation. Table VI-5.—Baseline EC Concentrations for Occupations With at Least One Value Exceeding Interim EC Limit Occupation Number of valid samples 8-hour full shift equivalent EC Concentration (μg/m 3 ) Minimum Median Maximum Diamond Drill Operator 1 1,561 1,561 1,561 Ground Control/Timberman 2 283 419 555 Washer Operator 4 272 337 621 Engineer 1 337 337 337 Roof Bolter, Mounted 12 76 258 818 Mucking Mach. Operator 23 12 257 671 Miner, Stope 14 77 218 479 Cleanup Man 2 51 217 384 Scoop-Tram Operator 7 10 210 449 Drill Operator, Rotary Air 21 0 185 1,041 Miner, Drift 17 12 175 1,122 Blaster, Powder Gang 134 5 175 1,031 Belt Crew 8 20 173 386 Roof Bolter, Rock 21 48 172 1,007 Truck Driver 252 0 162 1,216 Shuttle Car Operator (diesel) 3 73 154 323 Complete Load-Haul-Dump 32 14 145 634 Drill Operator, Jumbo Perc 38 4 137 845 Drill Operator, Rotary 75 2 132 853 Motorman 8 46 129 322 Front-end Loader Operator 214 0 121 2,291 Scaling (mechanical) 80 0 107 958 Supervisor, Co. Official 13 1 100 658 Utility Man 29 22 73 762 Scaling (hand) 26 14 67 1,548 Mechanic 34 0 64 323 Figure VI-1 depicts, by mine category, the percentage of baseline samples that exceeded the interim EC limit of 308 μg/m 3 . Underground metal mines exhibited the highest proportion of samples exceeding this limit, followed by stone and then other nonmetal mines. In the three trona mines sampled, 24 of the 25 samples were lower than the proposed limit. Across all commodities, 19.3% of the 1,194 valid baseline samples exceeded the interim EC limit. BILLING CODE 4510-43-U ER06JN05.007 Figure VI-2 shows how samples exceeding the interim EC limit were distributed over individual mines. One to 20 baseline samples were taken at each mine. In 115 of the 183 mines sampled (63%), none of the baseline EC measurements exceeded 308 μg/m 3 . The remaining 68 mines (37%) had at least one sample for which EC exceeded 308 μg/m 3 . All samples taken at 4 of the mines exceeded the interim limit. ER06JN05.008 BILLING CODE 4510-43-C (3) Relationship Between EC and TC The 2001 final rule stipulated that TC ( i.e. , EC + OC) measurements would be used to monitor and limit DPM concentration levels. Although it was recognized that TC measurements were subject to various interferences from non-DPM sources, MSHA believed that, in underground metal and nonmetal mines, it could effectively eliminate such interferences by a combination of selective sampling procedures and careful analytical techniques. During the 31-Mine Study, however, MSHA found no reasonable sampling method that would adequately protect TC measurements from interference by such sources of organic carbon as oil mist and ammonium nitrate fuel oil (ANFO). Furthermore, MSHA found that it was cumbersome and impractical to restrict its TC sampling so as to avoid potential interference from environmental tobacco smoke (ETS). Indeed, as indicated earlier, nearly one fourth of the TC samples collected during the 31-Mine Study (106 out of 464) had to be voided on account of potential interferences from extraneous sources of OC. Therefore, in concert with the Second Partial Settlement Agreement, the 2003 NPRM proposed to “[r]evise 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.” (68 FR 48668) Using EC as the surrogate permits direct sampling of miners (such as those who smoke, operate jackleg drills, or load ANFO) for whom accurate DPM monitoring would be difficult or impossible using TC measurements. Also in accordance with the Second Partial Settlement Agreement, the NPRM proposed to convert the existing interim exposure limit, expressed in terms of TC measurements, to a “comparable” EC limit by applying a specific conversion factor obtained from data gathered during the 31-Mine Study, as explained below. MSHA is adopting this proposal with the intention of providing at least the same degree of protection to miners as the existing interim limit. However, since it is unlikely that EC and OC have identical health effects, it is important to consider the extent to which the ratio of EC to OC (and hence of EC to TC) may vary in different underground mining environments. Unlike the 31-Mine Study, no special precautions were taken during MSHA's baseline sampling to avoid ETS or other substances that could potentially interfere with using TC as a surrogate measure of [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A05-10681. Public record. Not legal advice.