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Even though federal health officials have long recognized exposure to diesel fumes as a cancer risk, solid evidence for the link between breathing in chemicals contained in the vapor coming off engines has been lacking. In large part, the dearth of scientific evidence was due to intentional suppression of findings from a long-term study of cancer rates and deaths among miners. Now, those findings have been published in a series of articles in the Annals of Occupational Hygiene and the Journal of the National Cancer Institute. The facts cannot be encouraging for anyone who has spent a career working with and around diesel engines.

The Diesel Exhaust in Miners Study (DEMS) involved baseline health assessments and lifetime follow-up with a total of 12,315 workers in eight different mining facilities. Miners were tracked beginning in 1947 and through 1997. During the study period, a compound known as respirable elemental carbon, or REC, that is present in diesel fumes was measured in each mine’s air. Researchers recorded each time a miner was diagnosed with or died from lung cancer, while also noting whether the victims smoked or had other risk factors for the disease.

REC and lung cancer data collected through the study were analyzed by researchers funded by the National Cancer Institute and the National Institute of Occupational Safety and Health as early as the late 1990s. Mining companies, fuel producers and members of the U.S. Congress, however, repeatedly blocked publication of the analyses because the corporations and their patrons did not like the conclusions.

Specifically, the groups and politicians who worked to keep the DEMS results out of print wanted workers and the public in general to remain ignorant of the fact that long-term exposure to diesel exhaust fumes results in higher rates of lung cancer. Employees with the highest levels of exposure to diesel fumes developed and died from lung cancer at rates about three times higher than did workers with the least on-the-job exposure.

The mortality analysis appears in the March 2012 Journal of the National Cancer Institute under the title "The Diesel Exhaust in Miners Study: A Nested Case-Control Study of Lung Cancer and Diesel Exhaust." The authors, led by Debra T. Silverman, with NCI's Division of Cancer Epidemiology and Genetics, found "a statistically significant exposure–response relationship after we adjusted for possible confounding from smoking and other established and hypothesized lung cancer risk factors. The exposure–response curve showed a steep increase in risk with increasing exposure at low-to-moderate levels."

In plain language: Breathing diesel fumes puts people at significant risk for lung cancer. More exposure to diesel fumes is worse for people's long-term health, and diesel fumes are a separate cancer risk from cigarette smoking. It's worth noting, too, that the mortality study also revealed significantly elevated rates of esophageal cancer and pneumoconiosis.

Regarding the effect of cigarette smoking and exposure to high levels of diesel exhaust, Silverman and her coauthors wrote, "Little is known … . If our observation of attenuation [i.e., no increase in cancer] of the smoking effect in the presence of high levels of diesel exhaust is confirmed, several possible mechanistic explanations are apparent. First, at high levels of diesel exhaust exposure, PAHs [polyaromatic hydrocarbons] … and related compounds could compete with the metabolic activation of PAHs in tobacco smoke, leading to enzyme saturation. For example, PAHs in complex mixtures have been shown to have less than additive genotoxic effects at higher exposure levels. Second, constituents of diesel exhaust may suppress enzymes that activate or induce enzymes that detoxify carcinogens in tobacco smoke."

Again, what this would means is that diesel fumes exposure is a separate cancer risk from smoking.

While DEMS considered only the health of underground miners, Silverman et al. noted, "We observed an increased lung cancer risk associated with diesel exposure … as well as among other diesel-exposed occupational groups including truck drivers, railroad workers, dock workers, and bus garage workers."

They continued:

Our findings are important not only for miners but also for the 1.4 million American workers and the 3 million European workers exposed to diesel exhaust and for urban populations worldwide. … Thus, if the diesel exhaust/lung cancer relation is causal, the public health burden of the carcinogenicity of inhaled diesel exhaust in workers and in populations of urban areas with high levels of diesel exposure may be substantial.

I am not a doctor, statistician or cancer researcher. But as a Virginia (VA) personal injury attorney who has helped several retired railroad workers receive compensation from rail companies that negligently exposed them to cancer-causing toxic chemicals, I have seen firsthand how harmful years and decades of breathing diesel fumes can be. All railroads — Amtrak, BNSF, CSX, Norfolk Southern, Union Pacific and every other one — should take particular note of the DEMS findings. In light of what has been revealed, railroads should redouble efforts such as introducing electric battery-powered yard engines to not only save money, but save lives.


About the Editors: The Shapiro, Lewis & Appleton personal injury law firm, which has offices in Virginia (VA) and North Carolina (NC), edits the injury law blogs Virginia Beach Injuryboard, Norfolk Injuryboard and Northeast North Carolina Injuryboard as pro bono services.

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