Urban Air Quality
Few places pose greater air quality challenges than large cities. Urban areas are densely populated, giving air pollution plenty of victims to affect. All those people generate air pollution too, chiefly in the form of automobile emissions. But urban areas also have concentrations of industries that contribute their own share of air pollution.
Urban air quality varies around the globe. It's effected by geography, weather patterns, transportation, and industry. Watch for the effects of urban air quality on your health.
Laws governing the emissions of smoke and soot date back to the 1880s in Chicago, Illinois. Today, urban air quality is heavily regulated by federal, state, and local governments. The U. S. Environmental Protection Agency (EPA) closely monitors six air pollutants found commonly across the nation. They are: Carbon Monoxide, Lead, Nitrogen Dioxide, Ozone, Particulate matter with aerodynamic size less than or equal to 10 micrometers, and Sulfur Dioxide. These six "criteria pollutants" contribute to poor urban air quality.
Ozone is of particular concern to urban air quality managers. Ozone forms when vehicle emissions interact with sunlight. Temperature inversions, common over large urban areas, can trap ozone beneath a layer of cool air. Ozone causes shortness of breath, irritation of the nose, mouth, throat and lungs, and can be life-threatening to people with heart or lung disease. "Ozone alerts" are common in urban air quality management areas during the summer months, when temperatures are warm and the sun shines for longer periods.
Higher altitudes generally have stronger, more persistent winds, which blow away air pollutants. Cities such as mile-high Denver, Colorado, tend to have fewer ozone alerts than cities such as Los Angeles, which lies at sea level with mountains to the east that trap the air pollution blown by ocean winds. Urban air quality management is more difficult in low-lying, relatively wind-less cities.
Acid rain is a problem in some urban air quality management areas, particularly those near cities noted for heavy industry. Sulfur dioxide emissions interact with water vapor to form sulfuric acid, which precipitates in the form of rain. Acid rain causes damage to structures and roads, and can be irritating to people with sensitive lungs and skin.
There has been remarkable success in improving urban air quality. The Clean Air Act gave the EPA regulatory powers that have helped reduce urban air pollution levels by 90 per cent since the 1970s. None the less, urban air quality remains precariously balanced on the thresholds of EPA acceptable limits. One reason is that the EPA keeps lowering those limits, trying to force cities to clean up their urban air quality even more.
There are several things urban residents can do to help improve urban air quality. Chief among them is to reduce driving by automobile, the source of about 60 per cent of urban air pollution. Car pooling and taking public transportation can help improve urban air quality, as can bicycling or walking to and from work. Wood-burning fireplaces and charcoal-fueled barbecue grills contribute to poor urban air quality, and should be avoided in favor of cleaner-burning gas alternatives.
Urban air quality is much better today than it was at the beginning of the Industrial Age. Still, we cannot take for granted the gains since 1970. Urban air quality improvements will come only at greater cost and sacrifice. Watch the effects of air pollution on health because it can be especially harmful in urban areas.