Smog and population health

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Temps de lecture : 2 minutes  

Health Effects of Smog

Air pollution affects individuals differently, depending on factors such as age, health status, activity levels, socioeconomic status, and exposure levels. Effects range from minor irritations of the respiratory tract and small biochemical or physiological changes, to breathing difficulties, coughing, reduced lung functioning, aggravation of existing respiratory and cardiovascular conditions, and possibly genetic mutation.

Studies demonstrate that incidents of elevated air pollution levels are associated with increased rates of doctor’s visits, hospitalization, and premature death. […] The number of people affected decreases in correlation with the severity of air pollution effects.

Thus, while the impact of air pollution on any individual’s health may be relatively minor, the fact that it affects a large proportion of the population makes this an important issue in population health. As for the most severe cases, Health Canada estimates that short-term exposure to air pollution contributes to 1,800 premature deaths in the country annually, while an additional 4,200 Canadians die prematurely each year due to the long-term effects of exposure to air pollution.

The Science of Air Pollution and Health

Understanding of the possible links between air pollution and health has advanced greatly over the past decades. Experts agree that both short-term and long-term exposure to air pollution pose significant risks to human health.

The mechanisms by which these health effects occur are being revealed through ongoing research, but knowledge on the subject is still incomplete. Ozone is known to affect lung functioning in a variety of ways, causing inflammation in the respiratory tract and damage to lung tissue and contributing to reduced inhalation capacity and lung functioning. Particulate matter (PM) is also known to cause irritation and inflammation, and researchers have outlined a plausible mechanism linking PM to cardiovascular effects associated with air pollution exposure. PM triggers an inflammatory process in the lungs that has been shown to lead to accelerated atherosclerosis (plaque build-up), which raises the risk for heart attacks and strokes.

Epidemiological studies have produced significant evidence linking elevated daily levels of ground-level ozone, particulate matter and sulfur dioxide to increased rates of hospitalization, respiratory diseases, and premature deaths in cities across North America and Europe. Recent studies have drawn on large data sets spanning multiple urban areas and many years, providing increasingly convincing evidence of the short-term effects of air pollution on human health.

Likewise, studies have been highlighting the long-term effects of air pollution on human health, particularly since the 1990s. Following on two prominent studies in the previous decade, a 2002 study covering 500,000 people in more than 100 cities for a period of 16 years again confirmed a positive correlation between long-term exposure to fine particulate air pollutants and the risk of lung cancer and cardiopulmonary mortality.

A recent line of research concerns the potential for air pollution to trigger genetic, and therefore hereditary, mutations in humans and wildlife. Researchers from McMaster University have published results indicating that exposure to urban and industrial pollution can pose an increased risk of hereditary mutations in rodents and birds, identifying particulate matter as a principal factor in the increased mutation rates.

Particulate matter is still being vigorously researched; the focus of investigations has shifted away from whether there is a health impact, to what characteristics of PM determine toxicity and which sources of PM pose the greatest risk to human health. Uncertainties regarding the human health effects of air pollution remain, as do sceptics; however, taken as a whole, the scientific evidence on the subject is striking enough to have motivated action by governments around the globe. […]

Erica CRAWFORD et Tim WILLIAMS

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