Diesel Engine Exhaust is Carcinogenic, WHO Says
The agency found that diesel exhaust is a cause of lung cancer and also noted a positive association (limited evidence) with an increased risk of bladder cancer.
The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), recently classified diesel engine exhaust as carcinogenic to humans, based on evidence that exposure is associated with an increased risk for lung cancer, according to the agency.
In 1988, IARC classified diesel exhaust as probably carcinogenic to humans. An Advisory Group that reviews and recommends future priorities for the IARC Monographs Program had recommended diesel exhaust as a high priority for re-evaluation since 1998.
There has been mounting concern about the cancer-causing potential of diesel exhaust, particularly based on findings in epidemiological studies of workers exposed in various settings. This was re-emphasized by the publication in March 2012 of the results of a large U.S. National Cancer Institute/NIOSH study of occupational exposure to such emissions in underground miners, which showed an increased risk of death from lung cancer in exposed workers.
The scientific evidence was reviewed thoroughly by the Working Group and overall it was concluded that there was sufficient evidence in humans for the carcinogenicity of diesel exhaust. The Working Group found that diesel exhaust is a cause of lung cancer and also noted a positive association (limited evidence) with an increased risk of bladder cancer.
The Working Group concluded that gasoline exhaust was possibly carcinogenic to humans, a finding unchanged from the previous evaluation in 1989.
Large populations are exposed to diesel exhaust in everyday life, whether through their occupation or through the ambient air. People are exposed not only to motor vehicle exhausts but also to exhausts from other diesel engines, including from other modes of transport (e.g. diesel trains and ships) and from power generators.
Increasing environmental concerns over the past two decades have resulted in regulatory action in North America, Europe, and elsewhere with tighter emission standards for both diesel and gasoline engines. For diesel engines, this required changes in the fuel such as marked decreases in sulfur content, changes in engine design to burn diesel fuel more efficiently, and reductions in emissions through exhaust control technology.
While the amount of particulates and chemicals are reduced with these changes, it is not yet clear how the quantitative and qualitative changes may translate into altered health effects, and research into this question is needed, IARC said.
“The main studies that led to this conclusion were in highly exposed workers,” said Kurt Straif, M.D., MPH, Ph.D., head of the IARC Monographs Program. “However, we have learned from other carcinogens, such as radon, that initial studies showing a risk in heavily exposed occupational groups were followed by positive findings for the general population. Therefore actions to reduce exposures should encompass workers and the general population.”
The summary of the evaluation will appear in The Lancet Oncology as an online publication ahead of print on June 15, 2012.