After a weeklong meeting of international experts in Lyons, France, the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), has classified diesel engine exhaust as a known carcinogen to humans.  The declaration was based on what the WHO says is “sufficient evidence that exposure (to diesel fumes) is associated with an increased risk for lung cancer.”  Researchers also said that diesel exhaust was a possible cause of bladder cancer.

The last time the agency evaluated diesel exhaust was in 1998.  The new ruling raises the toxin to the level of secondhand cigarette smoke and other hazards including asbestos, alcohol, and ultraviolet radiation.  An advisory group within the IARC had recommended that diesel exhaust be reevaluated.  Over the ensuing years, there has been growing concern about the cancer-causing potential of diesel exhaust.  This was re-examined in the results of a large U.S. National Cancer Institute/National Institute for Occupational Safety and Health epidemiological study of workers exposed to diesel emissions in various settings such as underground miners who showed an increase risk of death from lung disease.  This research was published in March 2012. 

In a statement, Dr. Kurt Straif, head of the IARC Monographs Program, said, “The main studies that led to this conclusion were in highly exposed workers.  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 public.”

Many people are exposed to diesel exhaust, including pedestrians, ship passengers and crew, railroad workers, truck drivers, miners and those who operate heavy machinery.  The problem is worse in poor nations where vehicles, generators, and farm and factory equipment commonly release smoke and particulates into the air.  Growing concerns over diesel exhaust have resulted in regulatory action in North America, Europe and other locations with tougher emission standards for both gasoline and diesel engines.

In a statement, Allen Shaeffer, executive director of the Diesel Technology Forum, which represents car and truck companies and other makers of diesel engines, said, “New technology diesel engines, which use ultra-low sulfur diesel fuel, advanced engines and emissions control systems, are near zero emissions for nitrogen oxides, hydrocarbons and particulate matter. In the U.S. for example, diesel exhaust is only a very small contributor to air pollution. EPA’s most recent data indicates that diesel accounts for less than six percent of all particulate matter in the air.”  He added that advancements in clean diesel technology have been successful in improving air quality and also reducing greenhouse gas emissions.

The U.S. Department of Health and Human Services Public Health Services National Toxicology Program declared that diesel exhaust particulates are known to be a human carcinogen based on elevated lung cancer rates in groups exposed to diesel exhaust in 1998.