When people think of air pollution, they tend to associate it with smog, acid rain, or other forms of outdoor air pollution. But have you ever considered the existence of indoor air pollution? The answer is yes—every year, many people experience health problems caused by indoor air pollution.

Indoor air pollution can include three broad types of pollutants: particulate matter, chemical pollutants, and biological contaminants.

Whether short-term or long-term, exposure to polluted air can lead to a wide range of health problems of varying severity.

Many people are particularly sensitive to air pollution, and this is especially true for children and the elderly. In particular, people with pre-existing health conditions—such as asthma sufferers or those with heart or lung problems—may experience worsening of their conditions due to air pollution.

Short-term exposure to polluted air can cause adverse physical reactions, including watery eyes (eye irritation), a runny nose, and discomfort in the throat and respiratory system. It may also lead to symptoms such as headaches and dizziness, depending on the pollutant and level of exposure. Furthermore, it can exacerbate conditions in people with asthma and other respiratory diseases. In London, England, during the “Great Smog” of 1952, high concentrations of air pollution were associated with approximately 4,000 deaths during the five-day episode, with estimates of about 12,000 total excess deaths when deaths in the following weeks and months are included.

Long-term exposure to polluted air affects physical health, increasing the risk of chronic respiratory conditions, lung cancer, and heart disease; severe or prolonged exposure can also affect the brain and other organs. It can also affect the lung development and function of growing children, while older adults and people with pre-existing conditions may be particularly vulnerable to its effects.

By conservative estimates, more than 500,000 people in North America lose their lives each year due to smoking. In the United States alone, smoking and secondhand smoke exposure cause more than 480,000 deaths each year, while tobacco-related illness accounts for an estimated 48,000 deaths annually in Canada.

The problem of air pollution has far-reaching consequences; whether in terms of lost productivity or expenditures on medical and nursing care, the economic losses can amount to billions of dollars annually, and this issue remains to be resolved.

By Michael Chiu, MWS, CI
Previously published in Ming Pao Daily News – Updated and Revised in 2026