Polycyclic aromatic compounds (PAHs) are created during burning of everything from oil to wood to cigarettes, and many are carcinogenic.

The smoke has caused emergency room visits to spike and potentially thousands of deaths among the elderly and infirm.

A sharp drop in daily emissions amid coronavirus lockdowns earlier this year had little lasting effect on the build-up of climate-warming carbon dioxide.

Smoke from fires near Argyle and Pubnico in Yarmouth County, Lake Alma in Annapolis County and Saturday Lake in Lunenburg County are affecting air quality.

The worst conditions on Tuesday in London are predicted to last between 4 and 8 p.m.

Environment Canada has issued a heat warning for much of Southern Ontario, as temperatures soar into the weekend.

The province has put out a request for contract bids, amid concerns the wildfire season and COVID-19 could combine to cause serious health issues.

Most major Canadian cities saw drastic improvements in air quality over the last two months as COVID-19 kept people at home instead of on the roads.

Satellite imagery shows the high levels of nitrogen dioxide over China went down as lockdowns and factory closures were enforced earlier this year, but it's starting to rise again as cases drop.

Edmonton's air quality rose to a 9 on the Air Quality Health Index at one point on Monday, a level that Environment Canada deems to be a "high risk" to people in the affected area.