Millions of people in North America have been advised to wear N95 masks outdoors due to poor air quality levels sparked by intense wildfires in Canada.
New York will begin distributing free masks on Thursday. Canada has said that people should wear a mask if they are unable to remain indoors.
The smog is expected to spread beyond New York to other East Coast areas.
Officials warn that the dangerously smoky conditions are expected to persist into the weekend.
People in several cities across the US woke up on Thursday to hazardous air quality conditions, including in Philadelphia and other parts of Pennsylvania. Other parts of the US, including large swaths of the Midwest and the South, are also under air quality alerts.
Much of the smoke is coming from Quebec, where 150 fires are burning. It is already Quebec’s worst fire season on record.
New York Governor Kathy Hochul said one million masks will be given to residents on Thursday.
“This is a temporary situation. This is not Covid,” she said at a news conference. The governor added that New York City buses and trains have high-quality air filtration systems that make them safe forms of travel.
Nicha Suaittiyanon, a 30-year-old tourist who was visiting New York City from Thailand, told Agence France Presse the weather was making her eyes itchy and watery. “It smells like someone is doing a barbecue,” she said.
someone is doing a barbecue,” she said.
Environment Canada said that conditions were worsening in Toronto on Thursday, as more smoke pours in.
The agency has recommended that anyone outdoors wear a mask.
“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.
In New York, an orange haze blanketed the city’s skyline and shrouded landmarks including the Statue of Liberty. The air quality in the city was rated the worst out of all major metropolitan areas on Wednesday, according to Swiss air quality company IQAir.
Zoos have brought animals indoors, and in New York, carriage horse rides have been suspended.
Public health officials have cautioned people not to exercise outside and to minimise their exposure to the smoke as much as possible, as the air poses immediate and long-term health risks.
Canadian officials say the country is shaping up for its worst wildfire season on record.
Experts have pointed to a warmer and drier spring than normal as the reason behind the trend. These conditions are projected to continue throughout the summer.
Fires across Canada have already burned more than 3.8m hectares (9.4m acres) of land – an area 12 times the 10-year average for this time of year.
More than 600 US firefighters have been sent to Canada to assist local officials. French firefighters have also been deployed.
Also on Wednesday, US President Joe Biden and Canadian Prime Minister Justin Trudeau held a phone call to discuss the current situation.
Climate change increases the risk of the hot, dry weather that is likely to fuel wildfires.
The world has already warmed by about 1.2C since the industrial era began, and temperatures will keep rising unless governments around the world make steep cuts to emissions.
How does wildfire smoke affect your health?
Experts say exposure to wildfire smoke can cause a litany of health issues.
Matthew Adams, a professor at the University of Toronto and the director of its Centre of Urban Environments, said immediate effects of inhaling wildfire smoke include shortness of breath, an elevated pulse, chest pain, or inflammation in the eyes, nose and throat.
“On these elevated air pollution days, we’ll see an increased number of visits to hospital,” Prof Adams told the BBC. “And the people that are visiting the hospital typically have a pre-existing respiratory disease.”
But wildfire smoke has also been linked to serious, long-term health issues like cancer or lung disease, Prof Adams said, specifically for people who live in areas that experience frequent forest fires.
This is caused by small particles in the smoke haze, he said, which can enter the bloodstream and other parts of the human body, causing possible DNA mutations and other health issues.
Prof Adams advised people limit outdoor exercise to avoid breathing in the wildfire smoke.
And in areas closer to the fires, herecommended wearing an N95 mask outside to block inhalation of most of the smoke particles.