What is smog?

Smog is a mixture of pollutants with ground-level ozone as the main component. Ground-level ozone is formed when nitrogen oxides and volatile organic compounds interact in the presence of sunlight. High up in the stratosphere, ozone protects the earth from harmful ultraviolet rays, but at ground level, it can be a harmful air pollutant.

About 95 per cent of nitrogen oxides that lead to the formation of smog, are produced when we burn fuels in our cars and trucks, or generate energy using combustion engines, combustion turbines, industrial boilers and power plants. Nitrogen oxides are related to other atmospheric problems such as climate changes and acid rain.

Volatile organic compounds are also necessary to produce smog. They come from the evaporation of liquid solvents and fuels such as gasoline or barbecue starter fluid, and from oil-based paint.

What causes summer smog?

On hot and sunny summer days, stagnant air can trap pollutants and, when combined with sunlight, result in unacceptable levels of ground-level ozone. Since ground-level ozone concentrations are generally highest when the sun’s intensity is at its maximum, smog levels peak in mid-afternoon, and fall rapidly in the evening when the sun goes down. The pollutants build up over time, so anything people can do to reduce individual contributions to smog is beneficial to air quality, not only on high pollution days, but every day.

What causes the smog in southern New Brunswick?

Most of the ground-level ozone over southern New Brunswick comes from the contribution of long-range transport of pollutants from the industrial areas of the U.S., such as the Boston to Washington corridor and the Ohio Valley.

Also, weather conditions and patterns in the Maritimes and the regions to the south and south-west can also affect ground-level ozone concentrations. Therefore acceptable smog levels can be exceeded in cloudy, as well as sunny weather, with an equal number of exceedances occurring both during the day and night.

What is the federal government doing about improving air quality and reducing smog?

The Saint John Smog Forecast program is an important step in the enhancement of Environment Canada’s national weather service. Through more advanced research, monitoring and technology, Environment Canada will continue to move beyond weather forecasting and grow as an environmental prediction organization. Advancements in the science and practice of predicting environmental changes will benefit all Canadians, by providing them the information they need to make effective decisions about their health and safety, property and state of the environment.

The federal government is working both nationally and internationally to implement agreements that improve the air quality in Canada. The federal government also works with the provinces as part of the Canadian Council of Ministers of the Environment (CCME), a major forum in Canada for discussion and action on environmental issues of national and global concern.

For further information, please contact:

Mike Howe
New Brunswick Weather Centre
Environment Canada
(506) 451-6015