For the first time, researchers have concluded that smog can cause asthma, rather than just aggravate it. In the 10-year study, being published in the British journal Lancet, investigators followed children participating in athletics in 12 Southern California communities. Six of the communities had some of the nation’s poorest air quality, while six enjoyed relatively clean air. The children in the smoggy areas were three to four times more likely to develop asthma than those in cleaner communities. The findings will bolster the case against the Bush administration’s current attempts to weaken clean air standards. Asthma, the leading chronic illness among young people, afflicts about 9 million children in the U.S. and accounts for millions of hours of lost time at school and work.