On the same day that Mine Safety and Health Administration, MSHA, announced a major new workplace examination rule for metal/non-metal mines, Assistant Secretary of Labor Joe Main also announced that MSHA is exploring further possible rulemaking to limit diesel exhaust at all mines – both coal and metal/non-metal. This morning, MSHA published in the Federal Register a “request for information” on diesel exhaust in mines (“RFI”), kicking off a 90-day comment period. MSHA seeks “information and data on approaches to control and monitor miners’ exposures to diesel exhaust.” Read on for a full analysis…

Taking a fresh look at fairly recent standards

MSHA’s current diesel exhaust or “diesel particulate matter” (“DPM”) standard in metal/non-metal is only a few years old, last revised in 2008, contested in litigation until 2010, and coming at the end of a series of rulemakings that began in 2001 (full disclosure: my colleagues and I represented the National Mining Association in challenging some of those rules).

The latest version of that M/NM rule, at 30 CFR 57.5060(b)(3), requires that a “miner’s personal exposure to diesel particulate matter (DPM) in an underground mine must not exceed an average eight-hour equivalent full shift airborne concentration of 160 micrograms of total carbon per cubic meter of air (160TC µg/m3).” It requires mine operators to use engineering and/or workplace controls to reduce exposures before allowing use of respiratory protection to help reduce exposures to the permissible exposure limit (“PEL”).

In coal, MSHA’s 1996 diesel rule required monitoring diesel emissions, using clean-burning engines, training miners in health risks and maintenance, and revised standards for approving engines and components. MSHA’s 2001 final rule in coal restricted the diesel emissions of certain equipment, requiring use of engineering controls to limit exposures, and instituted additional miner training.

In its RFI, MSHA touts sampling data in its possession (which it said it would post in the public docket), showing significant decreases in DPM exposure in recent years. MSHA says that from 2006 to 2015, average exposures of metal/non-metal miners decreased by 57% percent from 253TC to 109TC µg/m3. According to the agency, approximately 63% of these mines had average exposures below 100TC µg/m3 in 2015, with 75% below below 122TC µg/m3. “Overall,” says the RFI, “50% of the mines sampled have average exposures between 48TC and 122TC µg/m3.” MSHA noted that “newer light-duty equipment makes up about 66 percent of the total existing diesel-powered fleet.”

But, in announcing the RFI today, Mr. Main said that it’s “time to determine whether existing rules are adequate to protect miners’ health.” He added that “there’s evidence of miners being at risk . . . We know we’re in better shape today than when these regulations were crafted. It’s time for us to take a look back.”

Revisiting diesel exhaust

MSHA says that several developments since it issued its current diesel rules have caused it to request “input from industry, labor, and other interested parties on approaches that may enhance control of DPM and diesel exhaust exposures to improve protections for miners in underground coal and MNM mines.” The input will help MSHA decide what, if any, further regulatory actions are necessary.

In particular, MSHA says that it is revisiting diesel exhaust controls because “of the carcinogenic health risk to miners from exposure to diesel exhaust and to prevent material impairment of miners’ health.” In support of its new concerns, MSHA cites, in particular:

• The hotly-contested Diesel Exhaust in Miners Study (“DEMS”) performed by the National Institute for Occupational Safety and Health (“NIOSH”) and the National Cancer Institute (“NCI”). According to MSHA, that study, published from 2009 through 2012, “found that diesel exhaust exposure increases miners’ risk of death due to lung cancer.”

• The International Agency for Research on Cancer’s (“IARC”) follow-on decision in 2012 to classify diesel exhaust as a human carcinogen based on the DEMS study.

• A November 2015 evaluation by the Health Effects Institute, which also reviewed the DEMS study and a Trucking Industry Particle Study, finding those studies to be “well-designed and well-conducted” though noting that despite their strengths, “any effort at quantitative risk assessment will need to acknowledge some key uncertainties and limitations.”

• MSHA’s own Health Hazard Alerts relating to diesel exhaust following the IARC announcement.

• The fact that three states (West Virginia, Pennsylvania, and Ohio, in particular) have requirements for control diesel exhaust that exceed MSHA’s. According to MSHA, these states “require diesel powered equipment used in underground coal mines to include an exhaust emissions control and conditioning system” that meets certain DPM emissions limits. They also limit “ambient concentrations” of exhaust, and some limit ambient nitric oxide, as well. In addition, they require certain testing, examination, and maintenance records.

• According to MSHA’s briefing, it also received requests by “stakeholders” to review current rules in light of the latest information on scientific evidence, cost-effectiveness, and risk.

Seeking specific information

The RFI contains a long list of questions about equipment and controls that are in use in the mining industry, their cost, effectiveness, advantages, and disadvantages. Major areas of interest by MSHA include:

• In coal, lowering emissions limits for light-duty equipment. MSHA says it would like to determine “whether it is feasible to lower the emissions limits for non-permissible, light-duty, diesel-powered equipment to 2.5 g/hr of DPM or less.” Can the current generation of equipment meet or exceed a 2.5 g/hr standard? What challenges (administrative, engineering, and technological) would such a standard create? What costs? What would be the advantages and disadvantages of such a limit or of a requirement that meets current EPA standards? What percent of current equipment does not meet current EPA standards, and what modifications could occur to meet the EPA standard?

• Adopting stricter state coal-mine diesel standards. Since, MSHA says, three states have adopted additional diesel regulations, what are the advantages and disadvantages of MSHA adopting those same requirements?

• Testing and maintenance of light-duty, non-permissible equipment in underground coal mines. In coal, what would be the advantages, disadvantages, safety and health benefits, and costs of testing non-permissible, light-duty, underground diesel-powered equipment on a weekly basis for carbon monoxide as currently required for permissible equipment? What maintenance requirements are appropriate, and what testing and maintenance documentation should MSHA require?

• Types and effectiveness of exhaust after-treatment technologies in underground mines. What are some best practices for selecting and using after-treatment devices? What technologies are in use? What do they cost ? How effective are they? How durable? What sensors are built in? Are integrated systems used, and at what cost? “What are the advantages, disadvantages, and relative costs of requiring that all light-duty diesel- 27 powered equipment be equipped with high-efficiency DPM filters?”

• EPA Tier 4/4i-compliant equipment. MSHA seeks to understand whether, and to what extent, mine operators already are purchasing engines that comply with the latest EPA Tier 4 standards. Is such equipment used with after-treatment systems? How long has this equipment been in use and at what cost?

• Surrogates for measuring DPM other than total carbon. MSHA requests “information on alternative surrogates, other than TC [total carbon], to estimate a miner’s DPM exposure. What is the surrogate’s limit of detection and what are potential interferences in a mine environment? What are the advantages, disadvantages, and relative costs for using the alternative surrogate to determine a MNM miner’s exposure to DPM?”

• Sampling and analysis. Since reliably measuring DPM at such low levels has always been a problem, MSHA asks what “advances in sampling and analytical technology and other methods for measuring a MNM miner’s DPM exposure . . . may allow for a reduced exposure limit?”

• Best practices. Overall, MSHA asks the mining community to provide information on best practices that have succeeded for operators in reducing exhaust.

In short, MSHA’s questions appear geared toward collecting a vast amount of industry data and experience in controlling DPM since various regulations took effect in the last decade and a half. While the RFI is a very preliminary stage of possible rulemaking, it seems to hint that MSHA may view many mine operators’ significant successes in reducing exposure as a reason to lower the limits further, rather than a cause for celebration. It also may suggest that MSHA is considering mandating certain equipment, procedures, or maintenance, rather than simply setting an exposure limit that leaves operators free to decide how to comply.

Needless to say, it is not clear that MSHA even will proceed with rulemaking after receiving answers to its questions (and doubtful that it has time to do so before the end of the current administration). But, the RFI is an important opportunity for mine operators to be helpful to MSHA on the record in understanding these issues.

A renewed debate over the DEMS study and surrogates?

One question in many minds will be whether MSHA’s information request will kick up a new storm of discussion on several closely intertwined issues: the reliability of the DEMS study, what it really says about the levels at which DPM may be harmful, and how best to measure diesel particulate matter.

The DEMS study was embroiled in challenges, litigation, and questions about its transparency, approach, and reliability nearly from its start in 1992 until as recently as 2012 (full disclosure: my colleagues and I represented a number of companies and groups in that long-running litigation, especially the mines that had been participants in the study).

Yet, despite those questions about DEMS, the study served as a basis for MSHA’s earlier rulemaking on DPM (even before the study was complete), for the IARC finding in 2012, for the Health Effects Institute paper in 2015, and apparently for MSHA’s RFI today.

The history and potential future of this issue is a long tale. How MSHA’s latest action may re-kindle this discussion is worthy of a future blog post all its own. Suffice it to say, however, that MSHA’s specific reliance on that study (and its offspring), as well as MSHA’s specific questions about how to measure DPM, make a renewed focus on the study highly likely.