EPA: Smog-Busters Worsen Warming

Catalytic converters have gone a long way toward cutting smog from automobiles in the last two decades, but federal regulators say the devices are a growing cause of global warming, The New York Times reported Friday.

The Environmental Protection Agency says that converters, which break down smog-causing nitrogen and oxygen from car exhaust, are rearranging the compounds to form nitrous oxide - a potent greenhouse gas.

Nitrous oxide, known as laughing gas, is more than 300 times more potent than carbon dioxide, the most common of the greenhouse gases that trap heat in the Earth's atmosphere.

Nitrous oxide makes up about 7.2 percent of the gases cited in global warming, the EPA said in a study published this spring. Vehicles fitted with catalytic converters produced nearly half of that nitrous oxide.

"You've got people trying to solve one problem and, as is not uncommon, they've created another," Wylie Barbour, an EPA official who worked on the study, told the Times.

Automakers say they could fix the catalytic converters, but some environmentalists say the problem will exist as long as cars run on gasoline.

Nitrous oxide also comes from nitrogen-based fertilizer and manure from farm animals. It is not regulated because the Clean Air Act was written in 1970 to control smog, not global warming. No regulations exist to control gases that are believed to cause global warming.

Last winter, the United States joined other industrialized nations at a meeting in Kyoto, Japan, in agreeing to lower emissions of greenhouse gases to 5 percent below 1990 levels, over the next 10 to 15 years.

The U.S. Senate has yet to approve the agreement and no federal rules have been written. The EPA will seek public comment on its study.