Monday, December 22, 2008

Diesel Particulate - What Part of Probably Carcinogenic Don't You Understand?

BrooklynDodger(s) Comments: Diesel particulate matter is an IARC 2A carcinogen because there is "sufficient" evidence in laboratory studies, but human studies were considered "limited" by the last working group to take it up, in 1989. Despite multiple studies among truck drivers and railroad personnel showing increased lung cancer, including some controlling for smoking, it wasn't enough to pull the trigger on "known." With some justice, it can be argued that there's lots of other junk in the air on the road, gasoline engine exhaust if possibly carcinogenic, there's some evidence for particulate air pollution being associated with increased community cancer. Attributing the excess cancer only to diesel can be criticized.

The study quoted here strengthens the evidence in people, but the wording points to an intermediate step. IARC evaluates "exposure circumstances," and mixtures in addition to particular agents. Maybe a step to consensus is to evaluate the exposure circumstance of truck driving or exposure to vehicle exhaust - evidence for carcinogenicity of these exposures ought to be sufficient.

Emissions from compressed natural gas engines should be bioassayed. Lighter in weight than diesel, but many nanoparticles.

Environ Health Perspect. 2008 October; 116(10): 1327–1332.

Lung Cancer and Vehicle Exhaust in Trucking Industry Workers

Eric Garshick,1,2 Francine Laden,2,3,4 Jaime E. Hart,2,3 Bernard Rosner,2 Mary E. Davis,3,5 Ellen A. Eisen,6,7 and Thomas J. Smith3

src="" border=0>Abstract

"Background. An elevated risk of lung cancer in truck drivers has been attributed to diesel exhaust exposure. Interpretation of these studies specifically implicating diesel exhaust as a carcinogen has been limited because of limited exposure measurements and lack of work records relating job title to exposure-related job duties.
Objectives. We established a large retrospective cohort of trucking company workers to assess the association of lung cancer mortality and measures of vehicle exhaust exposure.
Methods. Work records were obtained for 31,135 male workers employed in the unionized U.S. trucking industry in 1985. We assessed lung cancer mortality through 2000 using the National Death Index, and we used an industrial hygiene review and current exposure measurements to identify jobs associated with current and historical use of diesel-, gas-, and propane-powered vehicles. We indirectly adjusted for cigarette smoking based on an industry survey.
Results. Adjusting for age and a healthy-worker survivor effect, lung cancer hazard ratios were elevated in workers with jobs associated with regular exposure to vehicle exhaust. Mortality risk increased linearly with years of employment and was similar across job categories despite different current and historical patterns of exhaust-related particulate matter from diesel trucks, city and highway traffic, and loading dock operations. Smoking behavior did not explain variations in lung cancer risk.
Conclusions. Trucking industry workers who have had regular exposure to vehicle exhaust from diesel and other types of vehicles on highways, city streets, and loading docks have an elevated risk of lung cancer with increasing years of work."

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