Diesel Exhaust – A Known Human Carcinogen and Potential Source of New Legal Claims


Since 1988, diesel exhaust has been classified as a probable human carcinogen. It was not until the summer of 2012 that government agencies, including the National Institute for Occupational Safety and Health (NIOSH) and the Environmental Protection Agency (EPA), concluded that diesel exhaust is a known human carcinogen. Workers in the mining, trucking, and vehicle maintenance industries are most at risk because of their proximity to diesel fumes, making them potential plaintiffs in a wave of new litigation.

Exposure to diesel exhaust has been linked to adverse health effects, including eye and nose irritation, headaches, nausea, and asthma. Recent studies have also confirmed that diesel fumes can cause lung cancer. A positive, albeit weaker, association has also been found between the fumes and bladder cancer. Diesel engines are the primary culprit behind the toxic exposures, contributing to elevated concentrations of carbon monoxide, carbon dioxide, and oxides of nitrogen that, once inhaled, impair overall lung function and create mutagenic changes on the cellular level.

Adding credence to NIOSH and the EPA's reclassification of diesel as a human carcinogen are recent scientific findings. The Journal of the National Cancer Institute reported in its August 2012 online issue findings that showed a statistically significant relationship between exposure to diesel exhaust and an increased risk of dying of lung cancer. These findings stemmed from a nested case-control study of 198 lung cancer deaths among a cohort of 12,315 mine workers exposed to diesel fumes underground. Scientists measured the exposure-response relationship for diesel exposure and lung cancer based on quantitative estimates of historical diesel exposure, adjusting for smoking and other potential confounders. More recently, in September 2012, Environmental Health Perspectives released findings that lung cancer mortality in the trucking industry increased with elevated cumulative exposures to elemental carbon, which is released through diesel exhaust, even when adjusting for confounding factors. This retrospective cohort study of over 31,000 men in the trucking industry estimated personal exposures to elemental carbon by reviewing employment and mortality records. These findings were analyzed relative to historical levels of elemental carbon measured in trucking terminals from 1971 through 2006, making these results all the more timely given the number of diesel engines on the road.

Critics of these studies generally argue, among other things, that exposure measurements rest primarily on a retrospective analysis of potential historical exposures, rather than actual exposures. They also question scientists' limitations in predicting changes in exposures over time and their ability to articulate quantitative risk estimates. Even with these limitations, however, the studies show a correlation between exposure to diesel exhaust and an increased risk of developing lung cancer and mortality.

The reclassification of diesel exhaust coupled with recent scientific findings is expected to lead to more stringent regulations and work practices effecting the mining, trucking, and vehicle maintenance industries and may even lead to litigation. Employers are bound by a variety of state and federal regulations and industry standards to help mitigate the risk of diesel exhaust on workers, including those propounded by NIOSH and the EPA. While compliance with these standards or industry practices may be as simple as turning engines off when at idle or installing proper exhaust ventilation, compliance with other regulations may be significantly more complicated. For example, employers may be required to mitigate the risks to workers by offering personal protective equipment, in addition to documenting how employees were fitted for the gear and sufficiently trained in how to use it to avoid potential legal liability. Employers may also shoulder the burden of providing adequate warnings to their employees, as well as providing a host of additional safeguards.

Employers may not be the only ones at risk of liability, however, following diesel's reclassification as a carcinogen. Manufacturers, suppliers, and distributors of products that use diesel may face litigation when people who inhale diesel fumes develop lung cancer.

To learn more about how the reclassification of diesel as a human carcinogen may influence your claims or industry, please contact David Governo at [email protected] or Lonna Carter at [email protected].