Non-metal miners who were exposed to high levels of diesel exhaust appear to have a considerably higher risk of developing and dying from lung cancer compared to other people, according to a new report published in the JNCI (Journal of the National Cancer Institute). The study, part of the Diesel Exhaust in Miners Study, was made by scientists from the NCI (National Cancer Institute) and NIOSH (National Institute for Occupational Safety and Health).

Debra T. Silverman, Sc.D. and team had set out to determine what the cancer risk might be from diesel exhaust exposure, with a focus on lung cancer. Their study involved data on 12,315 miners at eight mines, all of them non-metal facilities. There was one salt mine in Ohio, three potash mines in New Mexico, three trona mines in Wyoming, and one limestone mine in Missouri.

The researchers gathered data on only underground mines, because their heavy equipment tends to be run on diesel, and exhaust fume levels accumulate to higher levels than in other occupational settings, such as shipyards or trucking depots. The authors added that miners who work in underground mines are exposed to diesel exhaust fumes levels several times higher than the exposure experienced by the general population.

They only examined non-metal mines because there, there are low levels of other substances which are linked to cancer risk, such as asbestos, silica and radon.

Diesel fumes exposure health outcomes were reported in two complementary papers:

  • Document 1 (cohort study) – risk of death from any cause, with a focus on lung cancer. Data was used from the full study population.
  • Document 2 (case-control study) – details on deaths from lung cancer in the cohort study. The researchers gathered data on risk factors linked to lung cancer, such as current and past smoking status, previous employment in jobs with a high lung cancer risk, and a history of respiratory illnesses.

In both reports, there was an exposure-response relationship with higher risk at higher exposure levels.

Silverman said:

“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.”

The investigators combined data on historical exposure information with thousands of measurements of constituents of diesel exhaust levels in the air in each mine. They quantified diesel exhaust levels by measuring respirable elemental carbon, considered the best index of diesel exhaust when monitoring in underground mines. They used the same exposure measurements for both study analyses.

Cohort study leader, Michael D. Attfield, Ph.D., wrote that for underground workers who were the most heavily exposed to diesel exhaust, the risk of developing lung cancer was five times higher than for workers with the lowest exposure.

The case-control study results backed up those found in the cohort study, the authors wrote.

After taking into account lung cancer risk factors, such as smoking, etc., they found that for heavily exposed underground miners, the risk of developing lung cancer was three times higher.

Lifetime non-smoking miners’ risk of developing lung cancer increased according to their levels of diesel exhaust exposure.

Silverman said:

“These data are especially revealing as they show the effect of diesel exhaust in the absence of smoking.”

A non-smoking miner with the highest level of diesel fumes exposure had a seven times higher risk of developing lung cancer, compared to a non-smoker with the lowest exposure, the researchers wrote.

Joseph F. Feaumeni Jr. M.D., director, Division of Cancer Epidemiology and Genetics (DCEG) at NCI, said:

“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.”

Written by Christian Nordqvist