Diesel exhaust a human carcinogen concludes WHO's cancer panel

A panel of scientific experts convened by the World Health Organization's (WHO) International Agency for Research on Cancer (IARC) concluded today that diesel engine exhaust is carcinogenic to humans.   Previously, the IARC classification for diesel exhaust was "probably carcinogenic to humans," but with the publication of additional epidemiological and toxicological studies over the last 20 years, the expert panel determined there was sufficient evidence to change the compound's cancer designation.   The IARC panel wrote:

"The scientific evidence was reviewed thoroughly by the Working Group and overall it was concluded that there was sufficient evidence in humans for the carcinogenicity of diesel exhaust. The Working Group found that diesel exhaust is a cause of lung cancer (sufficient evidence) and also noted a positive association (limited evidence) with an increased risk of bladder cancer."

Just prior to IARC's announcement, the Diesel Technology Forum (DTF) issued a statement about clean-diesel technology.  The trade group suggests in its statement that the U.S. EPA and the California Air Resources Board say that diesel exhaust has few biological effects.  One reporter, who participated in the IARC's news conference, quoted from the DTF's statement which relates to the Advanced Collaborative Emissions Study (ACES).  That statement reads:

"This landmark study sponsored by U.S. Environmental Protection Agency, California Air Resources Board, industry and HEI suggest 'few biologic effects to diesel exhaust exposure.'"

The IARC officials were unable to comment on the statement given its vague nature, but responded by saying that the expert panel had reviewed hundreds of studies, and suggested that if such a study claiming "few biologic effects" was in the literature, they would have reviewed it.

I looked at the DFT's statement and wondered myself from where the phrase "few biologic effects to diesel exhaust exposure" came.  The group's press officer promptly sent me its source.  It comes from an April 12, 2012 news release from the Health Effects Institute (HEI), a non-profit research center jointly funded by the U.S. EPA and industry.  It reported some of the most recent findings. from ACES.  Specifically, laboratory rats and mice were exposed for 16 hours per day to diesel engine emissions that meet the U.S. EPA's 2007 exposure standards for fine particulate matter and other pollutants.  A review panel overseeing the ACES wrote a commentary to accompany the researchers' report which said:

“Overall, these results indicate that rats exposed to one of three levels of diesel exhaust from a 2007-compliant engine for up to 12 months, for 16 hours per day, 5 days a week, with use of a strenuous operating cycle that was more realistic than cycles used in previous studies, showed few biologic effects related to diesel exhaust exposure.”

I'm glad to know that rats and mice being exposed to very clean diesel engines are not currently showing evidence of biological harm.  Perhaps that bodes well for workers in diesel-heavy jobs, like underground mining, trucking, engine maintenance and construction, who, in the years ahead may be working in environments where clean-diesel is used exclusively.  In the meantime, the IARC classification of diesel exhaust as a human carcinogens means that employers and regulatory bodies have work to do to reduce workers' and communities' exposure to diesel exhaust.




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Good point, Celeste. It's comforting to know that the rats experienced "few biological effects" in the most recent lab studies. How that relates to current, real-world conditions for diesel-exposed workers is left unexplained. The Health Effects Institute reviewed the literature about workers in 1995 and showed strong links to both lung cancer and bladder cancer in studies published at that point. It's nice to see IARC catching up.

Indeed. It's nice to see IARC catching up. Now, what about our worker safety agencies at the federal and State level? It's probably time (if not long passed) for some workers and their representatives to ask OSHA or their State OSHA to propose a rule to protect some of the most heavily exposed workers, or ask their Members of Congress to direct OSHA to do so.