New Class of Pollutants

A Louisiana State University chemist has reported the discovery of a new class of pollutants known as “persistent free radicals” that are produced during combustion and can last a long time in the atmosphere. H. Barry Dellinger, speaking at a meeting of the American Chemical Society, said the persistent free radicals are produced when incomplete combustion from a factory or car engine produces fine particles such as soot. As gases from the combustion cool, altered versions of chemicals from the exhaust attach themselves to the soot, creating long-lasting free radicals. Most free radicals, which are atoms or molecules that are highly unstable and prone to reaction, last for less than a second before being neutralized. Dellinger noted he was unsure whether persistent free radicals were harmful to human health, but said epidemiological studies were needed. Fine particle pollution is estimated to cause 15,000 premature deaths a year in the U.S.