In hot weather, air pollutants react with sunlight to form ozone. Stagnant air exacerbates the reaction. This year’s hot spell has been the worst heat wave in five years, with cities from Raleigh, N.C., to Boston enduring nearly as many days above 90 degrees Fahrenheit as during the summer of 1988. Yet this summer Philadelphia has had just seven days of ozone advisories; New York City just four days; Washington just one. During the summer of 1988, Philadelphia had 23 advisories, New York City 21, Washington 12. Summer isn’t over yet, but so far the number of smog advisories is less than half of the 1988 total.
Most barometers of air quality have been showing positive trends for years. In Los Angeles, the smog capital, peak ozone readings have steadily declined since the 1950s. From 1982 to 1992 overall U.S. smog incidence dropped by 8 percent, even as population and production rose. Carbonmonoxide pollution went down 30 percent; airborne sulfur dioxide declined 20 percent; airborne lead fell 89 percent. “If you adjust for meteorology,” says Kay Jones, an airpollution analyst, “you find the underlying trend in smog is almost entirely positive.”
Rapid progress has been made against carbon monoxide, a winter pollutant that can cause respiratory distress, partly because a new “oxygenated” gasoline that reduces carbon-monoxide emissions was adopted last year in many cities. In 1985, New York City had 71 days that were out of compliance with the EPA standard for carbon monoxide; that number declined to two days in 1991 and zero day last year. Nationally, carbon-monoxide levels have been dropping sharply since 1990.
The 1990 Clean Air Act has accelerated this advance, mandating oxygenated gasoline and other reforms. But most of its provisions have yet to take effect. Since cars and trucks account for about two thirds of smog emissions, improvements in air quality are led by the continuing turnover of old, dirty cars. Models on sale in 1993 emit only about 1 percent as much pollution as those of two decades ago. Beginning in 1995, many cities will switch to a new gasoline formula that reduces the pollution content. John Seinfeld, a researcher at the California Institute of Technology, believes current law has “set in motion the necessary regulations to remove the automobile as a serious source of air pollution in the 21st century.”
Still, some of these rules may be reaching the point of diminishing returns. The strictures of the 1990 Clean Air Act were justified partly on the basis of the harsh smog in the summer of 1988. Today those figures increasingly appear to be a fluke, not a portent of a miasmic future. Regulations under the act will require many states and cities to impose such measures as mandatory car pools, restrictions on commercial parking and emission controls on businesses as small as neighborhood bakeries. These changes may turn out to be unnecessary.
Detroit is under regulatory pressure to invest many billions of dollars in a zeroemission car, a solution that mainly transfers emissions from the tailpipe to the power plant. Because 1997 emissions by gasoline-powered cars will be close to zero anyway, it’s not clear what the electric car would accomplish. A group of researchers led by Seinfeld thinks the zero-emission vehicle may not be necessary except in southern California. The quest for perfect, emission-free transportation could backfire if it results in higher auto prices that discourage buyers from junking old cars.
Further good news on air pollution appears likely. “if current trends bold, cities like Baltimore and Washington will meet EPA standards for ozone in two or three years, even if government does nothing new.” Jones predicts. Might children someday ask: Daddy what was smog?
