By Matt Watts

NEW YORK - The air quality in New York hit the worst levels ever recorded while hundreds of flights at the city’s airports were delayed due to smoke from a series of wildfires in Canada.

The concentration of pollutants in the air around New York City hit the highest levels ever recorded on Wednesday afternoon, more than doubling the previous record set the day before.

As smoke from hundreds of Canadian wildfires continued to billow south over the region, the air quality index hit 413, a level described as “hazardous” the New York Times reported.

Before Wednesday afternoon, the highest air quality index figure ever registered in the New York City region was recorded on Tuesday, when it hit 174, the newspaper said. The next highest was recorded more than 20 years earlier, on July 7, 2002, when the index hit 167 due to smoke from other Canadian wildfires, it said.

The air quality was also said to be to be at the worst level in the world, according to IQAir, which monitors global air quality.

Meanwhile the US Federal Aviation Administration (FAA) warned travellers to expect flights to be delayed by up to two hours at New York’s LaGuardia airport and nearby Newark International due to the smoke.

Some 800 flight delays at New York City airports were reported by 19.50 EST (03:50 BST), according to Flight Aware.

The air travel bottleneck has had a ripple effect, postponing flights at airports from Atlanta to Houston. Inbound flights to Philadelphia’s main airport were also affected.

About 250 flights were delayed at Toronto Pearson International Airport.

Schools across the US East Coast cancelled outdoor activities and millions of Americans were urged to stay indoors on Wednesday as smoke from the Canadian wildfires drifted south, blanketing cities in thick, yellow haze.

The US National Weather Service issued air quality alerts for virtually the entire Atlantic seaboard.

An estimated 98 million Americans from New Hampshire to South Carolina were under air quality alerts on Wednesday.

Health officials from Vermont to South Carolina and as far west as Ohio and Kansas warned residents that spending time outdoors could cause respiratory problems due to high levels of fine particulates in the atmosphere.

“It’s critical that Americans experiencing dangerous air pollution, especially those with health conditions, listen to local authorities to protect themselves and their families,” President Joe Biden said on Twitter.

"This is not the day to train for a marathon or to do an outside event with your children," New York Mayor Eric Adams advised. "If you are older or have heart or breathing problems or an older adult, you should remain inside."

Wildfire smoke is estimated to be 10 times more toxic than pollution from burnt fossil fuels, said Dr Lisa Patel, a physician based in California.

Wildfire smoke contains very tiny particulate matter, or PM2.5 – the tiniest pollutant yet also the most dangerous. When inhaled, it can travel deep into lung tissue and enter the bloodstream. It comes from sources like the combustion of fossil fuels, dust storms and wildfires, and has been linked to a number of health problems including asthma, heart disease and other respiratory illnesses.

Millions of people die each year from air pollution-related health issues. In 2016, around 4.2 million premature deaths were associated with fine particulate matter, according to the World Health Organization.

On Wednesday New York City‘s air quality was reported to be more than 56 times over the World Health Organization‘s safety limit.

US private forecasting service AccuWeather said thick haze and soot extending from high elevations to ground level marked the worst outbreak of wildfire smoke to blanket the Northeastern US. in more than 20 years.

Millions of people in North America have been advised to wear N95 masks outdoors due to poor air quality levels.

New York will begin distributing a million free masks on Thursday. Canada has said that people should wear a mask if they are unable to remain indoors.

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.

Already, 2,293 wildfires have burned in Canada this season, torching approximately 3.8 million hectares of land, well above the 10-year average of 1,624 fires and 254,429 hectares burned.