New York, Jun 8 (IANS): Millions of people in North America have been advised to wear N95 masks outdoors as smoke from Canada's wildfires is blowing across the US, making the air quality "unhealthy".

New York will begin distributing free masks on Thursday. Canada has advised people to wear a mask if they are unable to remain indoors, the BBC reported.

About 115 million people were under air quality alerts because of wildfire smoke and ozone from Texas to Vermont on Wednesday evening. For smoke alone, around 90 million were under alerts across 16 states in the US, NBC News reported.

Much of the smoke is coming from Quebec, where 150 fires are burning.

More than 15,000 residents are expected to be forced to evacuate in the province, officials said on Wednesday. It is already Quebec's worst fire season on record, the British news broadcaster reported.

Terming it a "temporary situation", New York Governor Kathy Hochul announced on Wednesday that New York would distribute one million masks to state residents on Thursday.

Environment Canada has said that conditions are worsening in Toronto on Thursday, as more smoke pours in.

"These fine particles generally pose the greatest risk to health. However, respirators do not reduce exposure to the gases in wildfire smoke," the Environment Canada statement said.

According to US National Weather Service (NWS), major metro areas such as Boston, New York City, Philadelphia, and Washington D.C. are expected to experience "unhealthy air quality" levels for all age groups through Thursday,

"It is important to limit time outdoors, as exposure to air pollutants can aggravate health problems such as asthma, heart disease, and lung disease. To ensure proper safety, take breaks when possible or wear a mask that will help protect you from the smoke," NWS said in a statement on Wednesday.

"Hazardous air quality levels will persist across the Northeast and Mid-Atlantic through Thursday before shifting westward into Ohio Valley on Friday," the US weather agency said.