Large areas of the United States are under serious air quality alerts right now, due to the Canadian wildfires in Ontario and Quebec.
The U.S. Environmental Protection Agency issued official alerts for Connecticut, Massachusetts, New Hampshire, Rhode Island, and Vermont, while the New York State Department of Environmental Conservation issued an air quality health advisory for eleven counties, including New York.
The health impact of wildfires include wheezing, coughing, shortness of breath, an elevated pulse, inflammation of the eyes/nose/throat, pressure in the lungs, chest pain, and even cognitive effects.
Pulmonologist David Hill, M.D., who sits on the American Lung Association’s National Board of Directors, explains that when fine-particle pollution “get[s] down into the respiratory space, they cause the body to have an inflammatory reaction to them.” Says Dr. Michael Niederman, a pulmonologist at New York-Presbyterian/Weill Cornell Medical Center, “The small particulate matter, some of the trapped gases can be irritating to the lung. They can potentially be injurious. In the short term, they can cause bronchial spasms.”

(Source: https://www.airnow.gov)
Meanwhile, according to professor Matthew Adams, director of the University of Toronto’s Centre of Urban Environments, “small particles in the smoke haze … can enter the bloodstream and other parts of the human body, causing possible DNA mutations and other health issues,”
Populations that are the most vulnerable are young children, older adults, people with pre-existing respiratory conditions, pregnant women, and companion animals, although all people should take precautionary measures.
Experts recommend:
• Remaining indoors as much as possible, especially important for people with pre-existing medical conditions.
• Keeping children indoors as much as possible (children are at greater risk since their lungs are still developing).
• Keeping companion animals indoors, with the exception of short bathroom breaks.
• Keeping windows closed and circulating indoor air with air conditioning or a fan.
• Wearing an N95 face mask when outdoors.
• Limiting strenuous outdoor physical activity.

(Source: https://www.airnow.gov/aqi/aqi-basics/)
You can check the air quality in the United States in real time by zip code with the EPA’s Air Now tool.