Electric cars may not be the green panacea they are billed as and may themselves cause pollution, adding toxic lead from their batteries to the environment.
Unless alternative batteries are developed, the cars may cause serious threats to public health even as they reduce smog, according to researchers at Carnegie Mellon University in Pittsburgh.
''We got the lead out of gasoline,'' said Chris Hendrickson, one of the researchers. ''I'd hate to see us slide back and release lots more lead in the environment.''
A conventional car uses a single lead-acid battery primarily for starting. An electric car may use two-dozen batteries or more, with a proportional increase in lead content. Those batteries would have to be replaced every 36,000 miles, according to the study.
Emissions from mining, smelting, and recycling the lead needed for batteries would expose those near industrial sites to dangerous doses of lead, researchers say.
Electric cars owe their popularity in part to the Clean Air Act, which set tough standards for limiting the level of ozone. To meet them, California and other states are demanding the introduction of ''zero emission'' vehicles by 1998, with 10 percent of all new cars meeting the zero-emissions test by 2003. The only zero-emission cars close to mass production are powered by electricity stored in conventional batteries.
In an article to appear this month in the journal Science, Lester Lave, an economist at Carnegie Mellon, together with Mr. Hendrickson and Francis McMichael, his colleagues in engineering, examine the impact of emissions associated with lead-acid batteries. Their study was funded by the National Science Foundation, IBM Corporation and AT&T.
According to their calculations, even an electric car made with advanced technology not yet available would push six times as much lead into the environment as a small Geo Metro automobile burning gasoline with the lead additives that were eliminated in the 1980s.
Other criticism has centered on pollution from power plants that generate electricity to charge the cars.