3 December 1998 | updated 17 December 1998

During a two-day meeting held at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina, a federal advisory board recommended that new substances are added to the US Congressionally-mandated Report on Carcinogens in its Ninth Edition. The National Toxicology Program advisory board recommended that diesel exhaust particulates be listed as "reasonably anticipated to be a human carcinogen".

In a separate, unanimously reached decision the board recommended adding environmental (second-hand) tobacco smoke to the list of known human carcinogens. That surprising decision would bolster federal efforts to curtail smoking. It could be also cited by the US EPA in its court battle with the tobacco industry over the effects of environmental smoke.

Several chemicals that are contained in both diesel exhaust and tobacco smoke have been already listed as known carcinogens, as well as the smoke inhaled directly by smokers.

The advisory panel voted 9-3 to list alcohol as a known carcinogen despite studies indicating that moderate drinking may be beneficial for some peoples’ health.

The board rejected a proposed listing of the gasoline additive MTBE (methyl-tert-buthyl ether), which is used as an oxygenated and octane boosting gasoline additive in several US states. Consumers have complained about rashes and headaches after exposure to MTBE-doped gasolines. MTBE, due to its good solubility in water, is now being found in many areas of the US in groundwater and reservoirs, and to a lesser extent in drinking water supplies.

Altogether, changes in the classification for 11 substances have been recommended. The proposed changes will be publish in the Federal Register. The Federal Register publication will open a 60 day comment period before the final Ninth Edition of the Report on Carcinogens is published next year.

The adopted diesel emissions recommendation is likely to influence the position of the EPA on the issue of toxicity of diesel exhaust. The EPA has been in the process of developing an assessment of the possible health hazards from human exposure to diesel engine exhaust emissions. That document is still in a draft stage.

In August diesel particulate matter has been classified as a toxic air contaminant in California.

Contact: C. W. Jameson, (919) 541-4096