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Breathing Easier: Chemistry Professor Studies Ways to Lower Air Pollution
Related Links:
• Faculty
Observations Home Page
• Department
of Chemistry's Faculty Page
NOVEMBER 4, 2002--During the late 1940s, an epidemic struck some vegetation native to the Los Angeles metropolitan area. It was quickly noticed that the disease did not show an affinity for a particular species, but rather killed plants that chose to grow alongside the new, rapidly growing freeway system. Several years later, it was understood that this blight was the first sign of the air pollution problem now commonly referred to as smog.
Air pollution eventually became a concern nationwide, and in 1970, Congress passed the Clean Air Act (CAA), which set federal standards for air quality. We are now routinely reminded of this air quality issue, whether it is through the frequent reports in the popular media, local "ozone alerts," or the need to take one's car to a state emissions testing station every year or two. Given that the smog issue is still with us more than 30 years after the beginning of federal involvement in its regulation, the situation begs the question: "Is air quality getting worse or getting better?"
The latest reports in the media are not encouraging; the American Lung Association recently estimated that more than 142 million Americans breathe air that has unhealthy levels of smog (this figure represents about 75 percent of Americans who live in areas where smog levels are routinely monitored). The Ohio Environmental Protection Agency (EPA) recently revealed that 2002 was the worst summer for smog levels recorded in the last 14 years, with Lorain County (Oberlin’s location) registering 17 days of unhealthy smog levels, and Geauga County (a suburban region east of Cleveland) leading Northeast Ohio with 27 days of unhealthy smog levels. However, some cities, such as Denver and Los Angeles, have made impressive progress in significantly reducing the number of unhealthy smog days since the 1970s. This article is an attempt to understand the simultaneous worsening of air quality in some areas and improving air quality in others, as well as to illustrate the process by which air pollution public policy is informed by new developments in our understanding of the chemistry of the atmosphere.
In order to more fully understand the complexities of the smog issue, it is useful to begin by defining the term in a more scientific sense, and to understand its impact on health. The term "smog" originates from the joining of the words "smoke" and "fog," which was used to describe several deadly air pollution events in 1950s London. In that situation, a stagnant meteorological condition (fog) combined with the emissions of literally millions of coal-fired ovens (smoke) to create a deadly mixture of chemical compounds. Modern day atmospheric chemists use the term "smog" much more precisely to mean a mixture of the gaseous chemical compound ozone and small solid particles (which consist mainly of carbon, but may be chemically diverse in nature). It is worth noting that the same chemical compound, ozone, is a natural and beneficial substance that occurs high in the atmosphere and helps to shield the Earth’s surface from harmful ultraviolet radiation. However, the existence of ozone at the Earth's surface is problematic because of its toxicity towards animal and plant life.
For the past 20 years, medical studies have repeatedly shown that persons with respiratory diseases are adversely affected by exposure to ozone. However, the evidence that ozone could potentially harm people with healthy respiratory systems has been slower in coming. At the same time, childhood asthma rates in the United States have doubled since 1980, and researchers have long attempted to connect air pollution with this health epidemic. Very recently, a link was established between the development of childhood asthma and the number of hours that children spend outdoors in areas with high ozone levels. In particular, the study found that sedentary children showed a lower asthma rate than their more athletic counterparts. In other words, exercise in high ozone environments is found to actually lead to increased risk of the development of asthma in healthy children.
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