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Smoke from Canadian wildfires reached New York City and other parts of the Northeast on Wednesday, posing risks to residents’ respiratory health.

The National Weather Service issued an air quality alert for New York City and nearby suburbs in New York, New Jersey and Connecticut, from 11 a.m. to 11 p.m. on Wednesday. Young children, elderly people, and those with respiratory diseases like asthma are advised to avoid strenuous activities in the afternoon and early evening. New Yorkers can check up-to-date air quality at AirNow.

New York City has experienced the effects of Canadian wildfires before, most notably in June 2023, when the city was shrouded in smoky orange clouds. Public health and environmental researchers later identified an association with the degraded air quality and a spike in emergency department visits in the city for asthma.

Wildfire smoke poses a risk to respiratory health because it is a mixture of water vapor and pollutants like particle pollution — tiny droplets of soot, acids, metals, and other compounds — which can easily seep into homes, according to the U.S. Environmental Protection Agency. Inhaling particle pollution can result in minor health effects like eye and respiratory tract infections, or more severe ones, like the exacerbation of asthma, or heart failure.

A 2021 report from the American Thoracic Society found that wildfire smoke increases rates of respiratory medication use, ambulance calls, emergency department visits, hospital issions, and mortality of all causes. Children and older adults are especially at risk for hospitalization for asthma, and wildfire smoke may affect outcomes for those with diabetes and end-stage renal disease, according to the report.

When it comes to wildfire smoke, there is no safe level of exposure, and researchers at Stanford University have estimated that it is about 10 times as toxic as the air pollution generated from the burning of fossil fuels.

To limit detrimental health effects from wildfire smoke, the New York City Department of Health and Mental Hygiene recommends staying indoors with windows and doors closed, if temperatures allow. If the outdoor temperature is higher than 85 degrees, the Health Department recommends using an air conditioner, with the fresh air intake closed to prevent pulling polluted air inside. Those without air conditioners can seek out libraries, public buildings and other cool indoor spaces.

The agency also recommends using a portable air cleaner to filter the air, and wearing a well-fitting N95 or KN95 mask if you need to go outdoors.

Eliza Fawcett is a reporter covering public health in New York City for Healthbeat. Eliza at [email protected].

Healthbeat is a nonprofit news platform reporting on public health from Civic News Company and KFF Health News.

Eliza Fawcett is a reporter covering public health in New York City for Healthbeat.