The Center for Public integrity’s Jim Morris was the first to report that two long awaited cancer mortality studies of US workers exposed to diesel exhaust finds significantly elevated levels of lung cancer. Researchers with the National Cancer Institute (NCI) and CDC’s National Institute for Occupational Safety and Health (NIOSH) proposed the studies two decades ago, going great lengths to address methodological limitations identified in previous epidemiological studies of diesel exhaust-exposed workers. The bottom line, and with now stronger evidence than ever, there should be no question that diesel exhaust is carcinogenic to humans.
Underground miners in the U.S. are some of the workers most heavily exposed to diesel exhaust. By 1998, there were already dozens of studies showing elevated risk of lung cancer in groups of exposed workers (e.g., here, here, here, here) and the Mine Act directs the agency to issue health standards based on the “best available evidence.” For those reasons and because feasible controls were available to reduce miners’ exposure to diesel exhaust, the Labor Department’s Mine Safety and Health Administration (MSHA) proposed a rule to address this serious hazard. After public hearings and a comment period, MSHA staff worked to prepare the final rule to be published before the end of the Clinton Administration. The complication?
Members of Congress, including Senator Harry Reid, sent letters in June 2000 to Labor Secretary Alexis Herman urging her to delay issuing a final rule to protect miners from diesel particulate matter until the NIOSH/NCI epidemiological study was complete.
“you should issue your final rule after completion and review of the NIOSH study even though that may temporarily delay the final rule. …” [emphasis added]
A nearly identical letter was sent by Wyoming Senator Michael Enzi. The Senators also reminded the Labor Secretary of language in the FY 2000 appropriations bill directing that MSHA’s rulemaking on diesel be “informed” by the NIOSH/NCI study.
Then MSHA chief Davitt McAteer did not cave to the congressional pressure. He relied on the sound directive in the Mine Act to rely on the best evidence that is currently available. MSHA staff completed their work and a health standard to protect diesel-exposed underground miners was published in January 2001. Had McAteer and the Clinton Administration acquiesced to the calls for a “temporary delay,” MSHA would just now be preparing a final rule. Without the rule, underground miners were exposed to levels of diesel particulate matter (measured in total carbon) that averaged 800 ug/m3 per shift, and under the rule the maximum allowable shift average is 160 ug/m3. Multiply those exposure levels by 10 years of delay, and you can practically count the excess lung cancer cases.
I was employed at MSHA during the time its diesel rule was being develop, and we knew that the NIOSH/NCI studies were just barely getting underway. There was no doubt that it would be several years (optimistically) before these epi studies would be complete. We also knew, as I wrote in “Weight of the Evidence or Wait for the Evidence?” that an industry coalition was already using all kinds of tricks to obstruct the conduct of the NIOSH/NCI studies. (And that shenanigans continued through last month when the industry coalition sent letters to major scientific journals warning them against publishing the studies.)
Kudos to former MSHA chief Davitt McAteer and individuals in the Clinton Administration for issuing a rule 10 years ago to address miners’ exposure to diesel exhaust. The NIOSH/NCI studies reconfirm the risk to miners’ health, and punctuate the benefit of the rule on the books.