ABSTRACT
Historical extreme air pollution events, such as those experienced in London in the 1950s and 1960s, clearly demonstrated the potential of ambient air pollution to exacerbate cardiorespiratory disease, as reflected in premature mortality and admission to the hospital. In the intervening years, considerable effort has been made to reduce pollution from the combustion of fossil fuels. Several countries, including Canada and the U.S., have established new stringent guidelines and standards for air pollutants such as sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, and particulate matter. At present, Canadian National Ambient Air Quality Objectives for these pollutants are rarely violated.
