Diesel exhaust fumes linked to lung cancer among miners

By Dr. Ananya Mandal, MDMar 4 2012

A new study shows that exposure to exhaust from diesel engines increases the risk of lung cancer.

It has been known that diesel exhaust may be a probable carcinogen. But the 20-year study from the National Cancer Institute took a closer look in the Diesel Exhaust in Miners Study, which followed 12,315 miners working in eight underground nonmetal mining facilities. Data were collected on the miners' health and exposure to various elements and chemicals from the time when the mine company first introduced diesel-powered equipment (between 1947 and 1967) until the end of the study in 1997. They breathed varying levels of exhaust from diesel-powered equipment, levels higher than the general population encounters.

Researchers found a higher risk of lung cancer among workers exposed to elemental carbon, which was used as a marker for exposure to diesel exhaust. Those miners with the highest levels of exposure had three times the risk of developing lung cancer compared with those with the lowest exposure levels. Other exposures to agents such as silica, asbestos, dust and radon, had a smaller effect on the relationship to lung cancer. The study was released Friday by the Journal of the National Cancer Institute.

But even workers with lower exposures had a 50 percent increased risk, wrote lead author Debra Silverman, an NCI epidemiologist. Those miners were exposed to levels of exhaust that are comparable to what is seen in the air quality of some urban centers around the world. “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,” Silverman wrote. She pointed to some highly polluted cities in China, Mexico and Portugal that in past years have reported diesel exposure levels that over long periods could be comparable to those experienced by miners with lower exposures.

Litigation from some mining companies had delayed release of the study findings. A separate industry group not involved in that litigation said Friday that the study looked back at mines using decades-old equipment, and there's far less pollution from diesel engines today.

“Diesel engine and equipment makers, fuel refiners and emissions control technology manufacturers have invested billions of dollars in research to develop and deploy technologies and strategies that reduce engine emissions, now ultimately to near zero levels to meet increasingly stringent clean air standards here in the United States and around the world,” said Allen Schaeffer of the non-profit Diesel Technology Forum.

Later this year, the International Agency for Research on Cancer will meet to consider strengthening the classification of diesel engine exhaust from a probable carcinogen to a known carcinogen.

In an editorial accompanying the study, which appears in the Journal of the National Cancer Institute, Lesley Rushton of Imperial College London, said, “These results indicate that stringent occupational and particularly environmental standards for diesel engine exhaust should be set.”
Strict air-quality regulations in states such as California have helped reduce diesel engine exhaust. Earlier this week, the California Air Resources Board and diesel industry officials held an exhibit in Sacramento of new technology that has helped reduce emissions by 90%. The clean diesel initiative is aimed at lowering the health risks associated with exposure to diesel engine exhaust by 85% by 2020, according to ARB executive officer James Goldstene.