Major US study of air pollution enters final phase

The final phase of the nation's most comprehensive air-pollution study in more than a decade begins in southern California this month, when 200 scientists and technicians join forces to tackle the smog problem. The four-county South Coast Air Basin, with the most stubborn pollution problem in the country, will serve as an open-air laboratory for scientists trying to unravel the causes of air pollution.

One team of scientists will set up shop at the Grand Canyon to track the inland flow of pollutants by searching for gases released by colleagues along the southern California coast.

The $8.5 million Southern California Air Quality Study is expected to affect air-pollution control strategies into the next century and may eventually affect where residents in the basin live and work, and how they get there. The study may also give a better view on how gaseous emissions produce haze and affect the human respiratory system.