| 摘要 | There is no question that air pollution can kill. About 4,000 Londoners died during the infamous five-day “London Fog” of December 1952, when pollution soared tens of times higher than current peak levels, and visibility dropped as low as 20 feet. Today’s fears, however, center on the extent to which current, far lower air pollution levels can be harmful.
Regulators and environmental activists claim air pollution is still a major health threat. In its State of the Air 2006 report, the American Lung Association claimed “over half of the U.S. population lives in counties that have unhealthful levels of either ozone or particle [soot] pollution.” According to an Environmental Protection Agency (EPA) fact sheet, “ozone can irritate lung airways and cause inflammation much like a sunburn. . . People with respiratory problems are most vulnerable, but even healthy people that are active outdoors can be affected when ozone levels are high.”
Air pollution reductions are expensive, costing Americans at least tens of billions of dollars each year. Recently, the EPA implemented tough new standards for ozone and soot that will cost at least an additional $100 billion per year–or about $1,000 per household–and the agency plans to clamp down still further in the future.
The EPA attributes well over 90 percent of the benefits of its clean air programs to improvements in human health. Thus, a key policy question is whether EPA’s health-benefit claims are credible. Even as public health authorities and environmental activists become more strident in raising health alarms, evidence continues to mount that air pollution at contemporary low levels is causing little or no harm, even in the most polluted areas of the country.
More sober estimates in the EPA’s own technical analyses belie the scary claims it puts out for public consumption. Writing in the journal Environmental Health Perspectives, EPA scientists estimated that going from 2002 ozone levels, which were by far the highest of the past several years, to nationwide compliance with the stringent new federal eight-hour ozone standard would reduce respiratory-related hospital admissions and emergency room visits by no more than a few tenths of a percent.
Claims of an air pollution-asthma link by health experts have also been undermined by recent research. While the prevalence of asthma has nearly doubled in America during the past 25 years, air pollution of all kinds has sharply declined around the nation at the same time, making air pollution an implausible culprit.
Government-funded research by scientists from the University of Southern California supports this finding. The authors of the Children’s Health Study reported that children who grew up in areas with higher air pollution, including areas with the worst air pollution in the nation by far, had a lower risk of developing asthma. The researchers also found that ozone had no effect on lung development, even though the study included areas that exceeded the federal ozone standard more than 100 days per year. And even in a community with uniquely high soot levels–more than twice the current federal health standard–soot was associated with only a 1 percent to 2 percent decline in lung capacity.
The most serious claim about air pollution is that it prematurely kills tens of thousands of Americans each year. This claim is based on small statistical correlations between pollution levels and risk of death. But correlation doesn’t necessarily mean causation, as demonstrated recently by a number of embarrassing reversals of conventional medical wisdom.
The air pollution-mortality claim deserves even greater skepticism. First, it is based on the same unreliable correlation methods that have led medical authorities astray in other areas. Second, even though pollution is weakly correlated with higher premature mortality on average, it seems to protect against death in about one-third of cities. How could pollution kill people in some cities and save them in others? More likely, both results are chance correlations rather than real effects. Third, in laboratory experiments, researchers have been unable to kill animals by exposing them to air pollution at levels many times greater than ever occur in the United States.
It would be nice if we didn’t have to give up anything in order to achieve additional reductions in air pollution. But in the real world, the costs of air pollution control mean higher prices, lower wages and lower returns on investments, reducing the resources we have available for everything else that affects our health, safety and quality of life. If our air is already safe to breathe, then the EPA’s never ending war on air pollution is costing us much and providing little in return.
Why would regulators want to impose requirements that will cause net harm to the people they intend to protect? As a powerful, highly specialized agency with a staff that is passionate about air quality, the EPA unavoidably suffers from tunnel vision: the pursuit of a single-minded goal to the point where it does more harm than good. Environmental regulators will pursue the next increment of air pollution reduction, and the next, regardless of whether the increasingly marginal benefits are worth having or the costs worth bearing. By pursuing tiny or nonexistent health benefits at great cost, the EPA is making us worse off overall.
Joel Schwartz is a visiting fellow at AEI. |
