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Tough Rules Have Made Our Air Cleaner

May ushered in smog season and metro Atlanta had its first code orange alert Monday. We’ve made tremendous progress improving our air quality, but serious challenges remain, particularly with respect to elevated ozone levels.


Since the passage of the Clean Air Act amendments in 1970, emissions of regulated air pollutants in the United States have dropped 63 percent while at the same time, the U.S. population has increased by 50 percent and the size of our economy has more than quadrupled.

These improvements in air quality are the direct result of mandated reductions in emissions from industrial, energy and transportation sources.

Although politics certainly influence legislative and regulatory decision-making, the motivation behind the Environmental Protection Agency’s air quality regulations is not ideological.

Instead, the EPA is required by law to dispassionately evaluate the best available scientific evidence and take steps to minimize environmental risks to human health. The achievements of the past 40 years are indeed laudable and have resulted in saved lives and improved health for all of us.

At the same time, a large body of scientific research clearly indicates that levels of air pollution still commonly found in many parts of the U.S. continue to have harmful effects on the health of both adults and children.


For example, a long-term study involving thousands of children in Southern California found that children living in communities with higher levels of ozone and particulate matter had reduced lung function. When families moved to areas with better air quality, the children’s lung function improved. Likewise, when children moved from a community with good air quality to one with poor air quality, their lung function declined.

Unfortunately, if these reductions in lung function do not improve before a child reaches maturity, that individual likely will have a lifelong lung function deficit. Another finding of this study was that children who live in an area with poor air quality and participate in numerous outdoor sports are more likely to develop asthma than children in the same community who do not participate in these sports. In communities with low levels of ozone, participation in outdoor sports does not increase the incidence of asthma.

Here in Atlanta, scientists at Emory and Georgia Tech have been examining millions of emergency department visits to hospitals throughout metro Atlanta and have found a striking relationship between ozone concentration and emergency department visits for asthma. This relationship is observable after controlling for other factors that influence asthma such as temperature and the prevalence of communicable respiratory infections (which are much more common when children are in school).

For example, if you consider just days in July on which the maximum temperature is exactly the same, the number of emergency department visits for asthma is higher when ozone is higher. These findings do not suggest that all asthma emergency department visits are caused by ozone, but they do provide evidence that ozone levels are responsible for many of the asthma visits suffered by our children.

Many other studies conducted at cities around the world have observed similar patterns. Numerous investigators have found that asthma symptoms worsen and the use of asthma medication increases when the air quality worsens. In addition, many studies have shown that the health effects of air pollution are not limited to asthma or even to respiratory diseases. A common finding of air pollution epidemiology is that cardiovascular mortality is higher in areas with high levels of air pollution, even when controlling for other risk factors of cardiovascular disease.

For example, numerous studies in the U.S. and Europe have found that the risk of heart attack increases in the days following an increase in PM levels. Many of these associations are closely tied to traffic sources of air pollution and especially to diesel traffic. The biological mechanisms responsible for these health effects are well-understood in some cases, but in many other cases, researchers are still learning how air pollution acts to cause the effects we see.

In order to minimize the health risks of air pollution, each of us can take steps to reduce our exposure. For example, we can reduce exposure to ozone by going for a jog in the morning instead of the afternoon in summer or reduce exposure to particulate matter by not exercising downwind of a freeway. We also can reduce our contribution to the air pollution problem by driving less and using alternate forms of transportation.

But ultimately, major reductions in air pollution are the result of decisions made at the societal level. The air quality improvements of the past 40 years show that these changes are possible and that they will not cripple our economy. Recognizing problems and making decisions to improve the health of our children is simply good stewardship of our natural resources.


Roby Greenwald is a research assistant professor in the Department of Environmental Health at Emory University’s Rollins School of Public Health. Anne M. Fitzpatrick is an assistant professor in the Department of Pediatrics at Emory’s School of Medicine and directs the Asthma Clinical Research Program.






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