The US Court of Appeals for the DC Circuit ruled today in favor of the United Steelworkers and MSHA in their efforts to protect underground miners from diesel particulate matter (DPM).Â The mining industry plaintiffs have claimed for years thatÂ MSHAâs 2001 DPM health standard was neither scientifically valid nor feasible, but the three-judge panel denied the firmsâ request to review MSHAâs rule.Â In a decision written by Judge David B. Sentelle, the court said âwe can find nothing in the administrative record that would justify second-guessing the agencyâs conclusions.â
The court ruling relates to a mandatory health standard issued by the US Department of Laborâs Mine Safety and Health Administration (MSHA) to protect about 15,000 underground metal and nonmetal miners who are exposed to excessive levels of particulate matter generated by diesel-powered mining equipment.Â During the rulemaking process, which began in 1998, and after the 2001 final rule was issued,Â the MARG Diesel Litigation Coalition argued tenaciously that (1) MSHA had failed to demonstrate that DPM presented a heath risk to exposed miners; (2) MSHA could not reliably measure minersâ exposure to DPM; and (3) available controls were not technologically or economically feasible.Â The judges were not convinced by any of the industryâs arguments.Â Â
With respect to MSHAâs assessment of the risk to minersâ health, the court commented that
âMSHA corralled more than enough evidence in support of its risk assessmentâ and ruled the agency âadequately demonstrated that DPM presents a significant risk to the health and safety of miners.âÂ
âsubstantial body of scientific evidence has identified a statistically significant causal association between DPM exposure and lung cancer,â the ruling noted.
With respect to the industryâs argument that the rule was not feasible, the court dismissed all of the mine operatorsâ arguments, sayingÂ
âMSHA offered an abundance of evidence in support of its feasibility determination.âÂ
The judges dismissed the industryâs claims that feasibility assessments should only consider technologies that can be used in every type of mine.
âThe fact that some of the specific control technologies identified by MSHA cannot be used in every mine does not undermine the overall reasonableness of the agencyâs feasibility determination. â¦MSHA has never suggested that there is a one-size-fits-all approach for every mine to meet the DPM exposure limits.Â Rather, the agency has reasonably concluded that many different technologies can be effective in reducing DPM exposure, and it is up to each individual mine operator to choose the best mix of controls for that particular mine.Â Nothing in the Mine Act or the Administrative Procedure Act requires an agency to describe in detail how every single regulated party will be able to comply with the agencyâs rules.â
The 2001 final rule issued by MSHA set a final exposure limit of 160 ug/m3* perÂ shift (8-hour time-weighted average) and scheduled to take effect in January 2006.Â As a result of the industry's legal challenges to the rule and subsequent rulemaking by MSHA, that limit will now take effect in May 2008.
Read "Dog Tails, Canaries..." for a review of the January 9, 2007 oral arguments in Kennecott Greens Creek v. MSHA (D.C. Circuit).Â For more on the DPM issue, read the diesel particulate matter case study on SKAPP's website.
*measured as total carbon, a surrogate for DPM.
There's a dark side to this story. The limit of 160 mcg/m3 of elemental carbon is now a benchmark for occupational diesel exposure. Frankly, this is a 007 standard, which if applied to work situations outside the mines would set us back terribly.
There are about 10 studies in truck drivers and 10 in railroad personnel which observe excess lung cancer. Exposures to these populations are mostly in the range of 10 mcg/m3 and below.
Personally, this is more likely a particulate effect than something special about DPM.
However, congratulations to the Steelworkers, it's a long time since a win, and a first step to controlling this dangerous exposure.
MSHA's 160 ug/m3 (TC) level was set based on a feasibility determination, not on our belief that it was a safe level. In fact, in our risk assessment and using the most conservative risk estimates, we predicted at least 15 excess lung cancer deaths per 1,000 workers exposed at about the 160 ug/m3 level over a working lifetime. A shocking estimate of excess risk. Some may say that the 160 ug/m3 limit is now the occupational benchmark, but I would argue that some of the engineering controls (e.g., ventilation) are more challenging and expensive in underground mines which lead to MSHA's particular feasibility determination. In other occupational settings, a much lower exposure limit is likely feasible.