Emissions that contribute to smog in the Los Angeles area are drastically worse than previously estimated, air-quality officials admitted yesterday. The announcement marked a reversal of the usual optimistic rhetoric about California air quality, which has been steadily improving since the late 1980s. Now it seems that progress in eliminating the two most common pollutants that lead to smog is not as advanced as previously thought. The miscalculation is due to underestimated emissions from cars, trucks, and consumer products ranging from deodorant and hairspray to household cleaners. California is under federal mandate to improve air quality by 2010; failure to do so will have significant political and human health consequences. On the former front, the state could lose federal funding; on the latter, half of the state’s population would continue to be at risk of suffering the ill effects of dirty air, including headaches, asthma, heart attacks, and cancer.