Wildfire smoke and air quality updates: Northeast flights disrupted

Wildfire smoke contains fine particulate matter, known as PM2.5, which are microscopic solid or liquid droplets -- often 30 times smaller than the diameter of a human hair -- that can be inhaled and cause serious health problems, according to the EPA.

PM2.5 is considered unhealthy for "Code Orange" and sensitive groups once the Air Quality Index surpasses 100, according to AirNow, a website that publishes air quality data. Once the AQI surpasses 150, it is considered "Code Red," unhealthy for some members of the general public who may experience health effects, with sensitive groups experiencing more severe effects.

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-ABC News' Julia Jacobo

New York City Mayor Eric Adams updated residents on the current situation with the dangerous air quality due to the Canadian wildfires.

He said the city's Air Quality Index, or AQI, hit 484, the highest level on record, on Wednesday afternoon. Anything above 300 is considered hazardous, according to Zachary Iscol, the commissioner for the city's Office of Emergency Management.

"Tomorrow things may improve but an AQI over 150 is still considered dangerous," he told reporters.

Adams said all outdoor events in the city were canceled Thursday and urged private groups to do the same.

"The best thing is that [people] remain indoors," the mayor said.

He reiterated advisories to close windows and to wear a mask if anyone has to travel outside.

Schools were already planned to be closed Thursday, and no decision has been made about the rest of the week, according to the mayor.

Adams said the current forecast shows the situation should improve at the end of the week but warned that the situation can change.

"It is difficult to predict the movement of the smoke," he said.

One million N95 masks will be made available for people at state sites in New York on Thursday, Gov. Kathy Hochul announced on Wednesday.

Officials will distribute 400,000 masks at MTA stations, the Port Authority Bus Terminal, state parks and the Javits Center, Hochul said.

Approximately 600,000 masks will be available from NYS Div. of Homeland Security & Emergency Services, the governor said.

Hochul has urged New Yorkers to stay inside due to smoke from the Canadian wildfires.

The MLB has postponed Wednesday night's games between the White Sox and the Yankees, set to take place in New York City, and between the Tigers and Phillies, set for Philadelphia.

The Phillies-Tigers game was moved to Thursday and the Yankees and White Sox will play a doubleheader on Thursday.

The WNBA said Wednesday night's game between the Minnesota Lynx and New York Liberty, which was to take place in New York City, has been postponed due to the air quality.