MONTREAL -- A smog warning has been issued for the Greater Montreal area by Environment Canada.

"Smog especially affects asthmatic children and people with respiratory ailments or heart disease," the agency states. "It is therefore recommended that these individuals avoid intense physical activity outdoors until the smog warning is lifted."

The warning is due to forest fires in northwestern Ontario and Manitoba that are creating poor air quality in these areas.

According to the Quebec government, the short-term symptoms of breathing in air pollution are:

  • Eye irritation;
  • Wheezing or difficulty breathing;
  • Irritation and inflammation of the respiratory tract (coughing);
  • Shortness of breath, especially during physical activity.

The severity of these symptoms depends on a person’s health and the level of pollution they are exposed to, the government states.

You should consult a doctor as soon as possible if you have any of the following symptoms:

  • Chest tightness;
  • Pain when breathing deeply;
  • Difficulty breathing despite not having engaged in physical activity.

Experts warn the smoke could cause serious harm.

"When you breath in those particles they get into your lungs and into your blood stream," explained Jill Baumgartner, an assistant professor with the McGill Institute for Health and Social Policy.

Babies, seniors and those with breathing issues are most at risk, said Scott Andrew Weichenthal, assistant professor in McGill University's department of epidemiology, biostatistics, and occupational health.

As always, Société de transport de Laval (STL) commuters will be able to take a bus or shared taxi for $1 due to the smog alert.

Launched in 2008, the STL Smog Alert initiative promotes the use of public transit when air quality deteriorates.

Environment Canada expects conditions to gradually improve by Tuesday.