March 12, 2012

Diesel Exhaust and Lung Cancer Deaths in Miners

Woman in a mine.

In a study of miners, scientists found that heavy exposure to diesel exhaust increased the risk of death from lung cancer. The risk may also extend to other workers exposed to diesel exhaust, as well as people living in urban areas with higher diesel exhaust levels.

Several lines of evidence suggest that diesel exhaust may raise the risk of cancer, particularly lung cancer. The Diesel Exhaust in Miners Study was designed to closely examine the relationship between diesel exhaust and lung cancer. Researchers from NIH's National Cancer Institute (NCI) and the CDC's National Institute for Occupational Safety and Health (NIOSH) studied over 12,000 workers at 8 mining facilities.

The investigators selected underground mines because the heavy equipment used in these mines frequently runs on diesel fuel. Exhaust builds up in the fairly enclosed air of the mines to levels considerably higher than that inhaled by the general population. The researchers selected only non-metal mines to minimize other exposures that may be related to lung cancer risk, such as radon, silica and asbestos. To quantify exposure for each worker, the scientists collected thousands of diesel exhaust measurements in the air at each mine. They combined those data with historical exposure information, along with equipment and ventilation records.

The results appeared in 2 papers on March 2, 2012, in the Journal of the National Cancer Institute. The first included data from the full study population (the cohort study). The second (the case-control study) closely examined the lung cancer deaths in the cohort, adjusting for factors like smoking, employment in other high-risk jobs, and history of other respiratory diseases.

Both studies found that the risk of lung cancer death rose with increasing diesel exhaust exposure. The cohort study found that the risk of lung cancer death among heavily exposed underground workers was 5 times that of workers in the lowest exposure category. After taking into account smoking and other lung cancer risk factors, the researchers in the case-control study found a 3-fold higher risk of lung cancer deaths among heavily exposed workers.

Non-smokers with the highest level of diesel exposure were 7 times more likely to die from lung cancer than non-smokers in the lowest exposure category. “These data are especially revealing as they show the effect of diesel exhaust in the absence of smoking,” says Dr. Debra T. Silverman of NCI, lead author of the case-control study. However, this finding was based on small numbers and will need to be confirmed with further research.

“It was vitally important to undertake a large study of diesel exhaust and lung cancer based on a quantitative assessment of historical exposure, taking into account smoking and other potentially relevant factors in order to estimate lung cancer risk,” Silverman says. The results suggest that people in the general population who are exposed to high levels of diesel exhaust may also have a higher risk for lung cancer.

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References:  J Natl Cancer Inst. 2012 Mar 5. [Epub ahead of print] and J Natl Cancer Inst. 2012 Mar 5. [Epub ahead of print].