cooking, heating gas big part of mexico city smog, study says

the associated press

mexico city -- a new study suggests mexico city's smog may be caused largely by gas used for cooking and heating, but skeptical environmentalists said friday they believe auto and factory emissions still play a greater role.

leaking or poorly burned gas "play a major (perhaps the dominant) role" in the production of ozone, the major component of smog, in the valley where the mexican capital is located, said the study published friday in the journal science. donald r. blake and f. sherwood rowland of the chemistry department at the university of california at irvine gathered hundreds of air samples from 1992 to 1995 and found high concentrations of hydrocarbons characteristic of liquefied petroleum gas, which is used for cooking and heating.

environmentalists said friday that more research is needed to determine what role pollutants play in making this metropolitan area of nearly 20 million people one of the world's smoggiest. "we live in a fatal cocktail, and liquefied gas is one source of pollution, but i don't think it's the dominant one," said homero aridjis, leader of the environmental organization group of one hundred. previous studies have found the major causes of pollution to be emissions by cars and factories, as well as particulate matter suspended in the air.

the study said improved handling of liquefied petroleum gas and switching to a less polluting composition consisting mostly of propane could significantly reduce smog. alejandro calvillo, the energy director of greenpeace, mexico, said that the study's emphasis on controlling leaks is important, but the government should focus on reducing the use of fossil fuels entirely. "most of that gas is used to boil water" for drinking and bathing, calvillo noted. "solar water heaters could easily be used here, and cut cooking fuel use in half."