Like the rest of Southern Ontario, London experiences episodes of poorer air quality, or 'smog'. Ontario’s Ministry of the Environment, Conservation and Parks maintains a network of ambient air quality monitoring stations through the province, including one monitoring station in London.
Some people say that London has the worst air pollution in Ontario. However, the Ministry’s data shows that London air is really no different than other cities in Southern Ontario. Air pollution is a regional issue.
Most of London’s smog advisories are triggered by ground-level ozone on hot summer days. Most of the ground-level ozone we see comes from emission sources in the United States.
Unlike industrial cities such as Sarnia or Hamilton, London does not have large industrial sources of air emissions. Most of London’s air emissions come from a wide range of small sources – vehicles, lawn mowers, and solvent use in homes and in smaller industries. Electricity use during peak times (e.g., hot, sunny days) is another way that Londoners contribute to air emissions, as peak demand for power is met by gas-fired power plants.
Air quality has been getting better in London in recent years. In the late 1990s, the province’s criteria for ozone would be exceeded for about 90 hours every year. In the last five years, this criteria was exceeded only 1-2 hours every year on average. Newer car models have significantly lower tailpipe emissions. More people are using “low VOC” paints, inks, and other consumer products. Progress is being made on improving air quality.