Diesel exhaust is a serious cancer risk in miners.

Miners exposed to high levels of diesel exhaust face a dramatically increased lung cancer risk, a long delayed official US study has found. In a study of non-metal miners in the United States, federal government scientists reported that heavy exposure to diesel exhaust increased the risk of death from lung cancer.

The findings, delayed by a court challenge from a mine industry lobby group, were finally published on 2 March 2012 in two papers in the Journal of the National Cancer Institute. Michael D Attfield, who led one of the studies, found the risk of lung cancer among heavily exposed underground workers was five times the risk observed among workers in the lowest exposure category. The study also found a significantly increased risk of oesophageal cancer.

In a second study led by Debra T Silverman, where investigators took into account smoking and other lung cancer risk factors, the data showed a three-fold risk of lung cancer death overall and about a five-fold risk for heavily exposed underground workers. For never smokers, risk of lung cancer death increased with increasing diesel exhaust exposure. “These data are especially revealing as they show the effect of diesel exhaust in the absence of smoking,” said Silverman. Although based on small numbers, non-smokers with the highest level of diesel exposure were seven times more likely to die from lung cancer than non-smokers in the lowest exposure category.

“This landmark study has informed on the lung cancer risks for underground mine workers, but the findings suggest that the risks may extend to other workers exposed to diesel exhaust in the United States and abroad, and to people living in urban areas where diesel exhaust levels are elevated,” said Joseph F Fraumeni Jr, director of the National Cancer Institute’s Division of Cancer Epidemiology and Genetics.

In an accompanying editorial in the journal, Lesley Rushton, the epidemiologist at Imperial College in London who produced for the Health and Safety Executive (HSE) the revised UK estimate of workplace cancer risks, wrote: “These results indicate that stringent occupational and particu­larly environmental standards for diesel engine exhaust should be set and compli­ance ensured to have an impact on health outcomes.” The International Agency for Research on Cancer (IARC) is due to review diesel exhaust evidence in June. Some believe the US study could lead to the agency upgrading diesel exhaust from a “probably carcinogenic to humans” group 2a rating to group 1, a known cause of cancer in humans.

By Rory O’Neill

NCI news release and Q&A on the diesel exhaust and miners study. iWatch News. The Pump Handle. Hazards magazine.

Silverman DT, Samaniac CM, Lubin JH and others. The diesel exhaust in miners study: a nested case-control study of lung cancer and diesel exhaust, Journal of the National Cancer Institute, 2 March 2012. doi:10.1093/jnci/djs034 [ pdf].

Attfield MD, Schlieff PL, Lubin JH and others. The diesel exhaust in miners study: a cohort mortality study with emphasis on lung cancer. Journal of the National Cancer Institute, 2 March 2012. doi:10.1093/jnci/djs035 [ pdf].

Rushton L. The problem with diesel, Journal of the National Cancer Institute, 2 March 2012. doi: 10.1093/jnci/djs137 [ pdf].