## Facts

- MSHA issued three interrelated rules regulating diesel particulate matter (DPM) exposure in underground metal and non-metal mines, including exposure limits, monitoring using surrogates, and related protections and schedules.
- MSHA concluded, based on an extensive scientific record, that miners experienced high DPM exposures and that prolonged exposure was associated with respiratory and eye irritation, bronchial inflammation, and increased lung-cancer risk.
- Because no reliable direct DPM measurement method was available, MSHA used total carbon (TC), and later elemental carbon (EC), as surrogate measures for DPM.
- Industry commenters objected that TC/EC measurements could be distorted by other carbon sources (e.g., tobacco smoke); MSHA responded with sampling protocols to reduce interference and later refinement through EC.
- MSHA found the exposure limits technologically and economically feasible, citing available and emerging controls (ventilation improvements, filters, engine upgrades) and evidence that many mines already met the limits.
- The rules included medical evaluation and transfer rights for miners required to wear respirators, including transfer to non-exposed jobs without loss of pay.
- Mine operators and industry associations petitioned for review, arguing the rules were arbitrary and capricious, infeasible, and procedurally defective under the Mine Act and the APA.

## Issues

1. Whether MSHA’s determination that DPM poses a significant health risk was supported by the record and was not arbitrary and capricious.
2. Whether MSHA reasonably selected TC and EC as surrogate measures for DPM and reasonably addressed measurement interference.
3. Whether MSHA reasonably found the DPM exposure limits technologically and economically feasible.
4. Whether MSHA had statutory authority to require medical evaluation and transfer rights tied to respirator use, and whether those provisions were properly noticed.
5. Whether the final implementation timetable was a permissible logical outgrowth of the proposed rules under notice-and-comment requirements.

## Decision

- The court denied the petitions for review and upheld all three MSHA rules.
- The court held that MSHA’s risk assessment and health-risk findings were reasonable and supported by the record.
- The court upheld MSHA’s use of TC and EC as DPM surrogates and found MSHA’s responses to interference concerns adequate.
- The court upheld MSHA’s feasibility determinations, accepting a technology-forcing standard supported by evidence of controls and existing compliance.
- The court upheld the medical evaluation and transfer provisions as within MSHA’s authority and sufficiently foreshadowed in the proposal.
- The court held the final compliance schedule was a logical outgrowth of the proposed rulemaking.

## Legal Principles

- Under arbitrary-and-capricious review, courts defer to an agency’s reasoned evaluation of scientific evidence in health and safety rulemaking, and the agency need not wait for scientific certainty.
- An agency may regulate using surrogate measurements when direct measurement is unreliable or unavailable, so long as the surrogate choice and mitigation of known interferences are reasonably explained and supported by the record.
- Feasibility for occupational health standards may be satisfied where compliance is generally achievable through available or reasonably foreseeable controls; feasibility does not require cost-free or immediate universal compliance.
- The Mine Act permits MSHA to adopt ancillary protective measures reasonably related to protecting miner health, including medical evaluation and job-transfer protections linked to required respirator use.
- A final rule satisfies notice-and-comment requirements when its key elements, including compliance schedules and protective provisions, are a logical outgrowth of the proposal and the issues aired during rulemaking.

## Conclusion

The D.C. Circuit upheld MSHA’s DPM standards for underground metal and non-metal mines, concluding that MSHA reasonably assessed health risks, permissibly relied on carbon surrogates for monitoring, adequately supported feasibility, and validly adopted respirator-related medical and transfer protections and a phased implementation schedule.


Kennecott Greens Creek Mining Co. v. Mine Safety & Health Admin., 476 F.3d 946 (D.C. Cir. 2007)