Smog: causes and effects

Smog refers to a noxious mixture of gases and particles that often appears as a haze in the air. It has been linked to a number of adverse effects on health and the environment.

The two primary pollutants in smog are ground-level ozone (O₃) and particulate matter (PM). High levels of smog are typically associated with the summer due to the presence of sunlight and warmer temperatures. However, the smog problem actually occurs throughout the year, with winter smog (due to particulate matter contributions rather than ozone) being a serious concern when stagnant air causes a build up of pollutants in the air. This is usually caused by increased wood heating and vehicle usage in the winter months.

Health - Smog has been identified as contributing factors in thousands of premature deaths across the country each year, as well as increased hospital visits, doctor visits and hundreds of thousands of lost days at work and school.

Environmental problems attributed to smog include effects on vegetation, structures, and visibility and haze (mainly due to fine PM).

Reducing the effects of air pollution on the health of Canadians and their environment is a key commitment by the Government of Canada.

• Smog: history of terminology
• Winter smog