Through the media, residents often hear about the Air Quality Index (AQI) and alerts issued by the Ontario government. The level of this index (0–100 or higher) is determined based on the concentration of smog pollutants in the air.

Air pollution in Ontario typically originates from the United States and various adverse weather conditions; in some areas, where pollutant levels are more severe, the concentration of air pollution is relatively higher.
Ground-level ozone and particulate matter are the primary causes of smog. Ground-level ozone is a byproduct formed by the reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) (Note: Ground-level ozone is distinct from the ozone layer that protects the Earth from the sun’s ultraviolet rays). Particulate matter is generated directly by chemical substances and reactions, such as vehicle exhaust, industrial and agricultural pollution, and road dust.

According to statistics, hundreds of millions of people in North America live in areas with abnormal levels of air pollution that exceed safe health thresholds. The report points out that vehicle exhaust, toxic fumes from factories and power plants, and ash from indoor and outdoor wood burning are the primary sources of smog pollution.

Evidence shows that prolonged exposure to smog can shorten life expectancy. Particulate matter pollution can trigger heart disease, blood clots, lung cancer, and asthma attacks. Ground-level ozone can cause breathing difficulties and asthma attacks; children, the elderly, and people with asthma are at the greatest risk.

By Michael Chiu, MWS, CI
Previously published in Ming Pao Daily News