Links Between Air Pollution and Human Health Clarified

April 3, 2002
By David Suzuki

In the last 50 years, most of humanity has been transformed into urban dwellers, more at home in the city than any other environment. But this rapid rush towards urbanization has brought with it a host of problems, including air pollution, the consequences of which we are just beginning to recognize.

More than 75 percent of all people in developed nations now live in cities — a 50 percent increase since 1950. The developing world is urbanizing even faster, with twice as many people now living in urban areas as did 50 years ago. But developing nations are still more rural, with just 35 percent of citizens living in cities.

Nations like Australia, Canada, and the United States are extremely urban. A recent Canadian census, for example, revealed that more than half of all Canadians live in just four urban areas. All that concentrated humanity can foster wonderful cultural and scientific achievements, but it also intensifies energy and resource consumption in a small area. So although cities only cover about 1 percent of the Earth's surface, they draw in resources from all over the world and have a tremendous impact on the planet as a whole.

With so much energy use concentrated in a small area, it's no wonder air pollution is so widespread. Whether you live in Toronto, Sydney, Houston, or hundreds of other cities, breathing dirty air has become a fact of life. We see it all the time: a complex soup of air pollutants casting a haze over the land. In the first half of the 20th century, burning coal for heat and to power factories were the primary sources of air pollution. Today burning coal (now to produce electricity) still causes large amounts of air pollution, but transportation has become the primary culprit.

Studying the human health effects of air pollution has often been challenging, because it is difficult to isolate from other factors that also influence health, such as smoking, diet, and exposure to poor indoor air quality. But recent studies are now confirming what intuitively makes sense: Air pollution really does make us sick, and it may cause disease as much as it makes existing problems worse.

For example, a recent report, published in the Journal of the American Medical Association, found that breathing polluted city air is almost as damaging to health as living with someone who smokes cigarettes. The study, the largest of it's kind, looked at the causes of death of 500,000 people living in American cities. Researchers found that increases in fine airborne particles known as particulates (largely from fossil fuel combustion) substantially increases the risk of death from cardiopulmonary disease and lung cancer. Their conclusions held true even after compensating for risk factors like obesity and smoking.

Exactly how air pollutants increase the risk of death is not well known. But a recent study by researchers from the Universities of Toronto and Michigan has helped shed light on the causes. Their findings, published in the journal Circulation, found that exposure to particulates and ozone (another important ingredient in smog) constricts blood vessels and may trigger heart attacks in people with heart disease.

Other recent studies have found that children who are physically active and live in areas with high concentrations of ozone are more likely to develop asthma. Air pollution has long been thought to exacerbate asthma, but many researchers now suggest that it is also a cause of this common chronic illness.

Air pollution was once primarily the scourge of megacities like London, where coal smoke killed 4,000 people during one week in 1952. Cleaner-burning fuels have relieved some of the soot, but the massive growth of urban areas and the popularity of trucks and automobiles has created a new problem: photochemical smog. Its effects may not be as dramatic, but they may be just as insidious.

Copyright 2002, David Suzuki Foundation
All Rights Reserved

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