Report Warns of Motor Vehicle Toxics : 11 Tailpipe Pollutants May Cause Thousands of Cancer Cases

Eleven toxic substances from motor vehicles may be responsible for thousands of cancer cases in California over a 70-year period, according to a new analysis by the state Air Resources Board of risks from tailpipe pollutants.

The report, the first by the state on the cumulative health risks of a wide range of tailpipe toxics, will go to the state Legislature and appears certain to escalate the debate over what further limits should be placed on auto emissions, and how quickly.

It comes at a time of growing public concern about toxics in general, and a new focus on toxic air contaminants by regional air pollution authorities and state and federal lawmakers.

On Monday, President Bush is scheduled to unveil a comprehensive clean-air package that is expected to call for new emission controls and controls on gasoline volatility on grounds that they will not only reduce urban smog, but “greatly reduce toxic pollutant emissions,” according to a draft Administration document.

The state’s cancer estimates are based on an analysis of 11 of 25 toxic substances emitted by motor vehicles. The study estimated that the chemicals together could cause as many as 22,674 cancer cases if people were exposed to the toxic chemicals over a 70-year period.

However, ARB spokesman Bill Sessa said the risk estimates are based on emission controls in effect as of 1987.

“If you look at the continuing clean air benefit those emission control measures we have already put in place since then, those we intend to adopt in the next five years, that risk will be significantly reduced, perhaps as much as 40% or 50%,” Sessa said.

Five of the substances together account for 99% of the total risk. They are benzene, 1,3-butadiene, diesel soot, formaldehyde and acetaldehyde. Benzene and 1,3-butadiene alone account for 83% of the total estimated risk.

Auto makers and oil industry representatives are worried that the study will prompt new controls on toxics. They say the ARB report gives “a false sense of accuracy” by citing a specific cancer case estimate and contend that the actual number of cases could range anywhere from 0 to 22,674.

“If you’ll pardon the phrase, I’d hate to see more fuel thrown on the fire than necessary. The public is already concerned about toxics,” said Mark W. Nordheim, the environmental coordinator for Chevron Corp. and a spokesman for the Western States Petroleum Assn.

Richard T. Paul, manager of environmental health for the Motor Vehicle Manufacturers Assn. of the United States, also assailed the estimate as preliminary and lacking in scientific certainty.

On Thursday, the ARB voted unanimously to impose tough new controls on tailpipe emissions of hydrocarbons and carbon monoxide beginning with 1993 model cars. While the primary purpose of the controls is to reduce urban pollution since hydrocarbons are a major cause of photochemical smog, the controls will have the added impact of reducing concentrations of air toxics because benzene, 1,3-butadiene, diesel soot, formaldehyde and acetaldehyde are also hydrocarbons.