Millions of Americans in the Northeast are being advised to avoid strenuous physical activity outdoors due to unhealthy air conditions across six states.Air quality alerts have been issued for parts of New York, New Jersey, Maryland, Connecticut, Rhode Island, and Pennsylvania on Wednesday, with pollution levels expected to exceed safe thresholds.Why It MattersAccording to the Environmental Protection Agency (EPA), ozone exposure can irritate the respiratory system, leading to coughing, throat discomfort, and pain during deep breathing. It can inflame and damage the airways, increase vulnerability to infections, and worsen existing lung conditions such as asthma, emphysema, and chronic bronchitis.Even healthy individuals may experience symptoms, but those with lung diseases are at greater risk of more severe health impacts, the EPA said.What To KnowIn New York, the Department of Environmental Conservation issued advisories for nine counties, including New York, Bronx, Kings, Queens, Richmond, Nassau, Suffolk, Westchester, and Rockland.”When pollution levels are elevated, the New York State Department of Health recommends that individuals consider limiting strenuous outdoor physical activity to reduce the risk of adverse health effects,” the advisory stated.”People who may be especially sensitive to the effects of elevated levels of pollutants include the very young, and those with preexisting respiratory problems such as asthma or heart disease.”Connecticut’s Department of Energy and Environmental Protection issued a similar warning for southern parts of the state, including Fairfield, Middlesex, New London, and New Haven counties.An air quality alert was also published by the National Weather Service (NWS) for northeast Maryland, as well as the Baltimore City metro area and the Annapolis region.Additional air quality alerts are in effect for parts of Pennsylvania and Rhode Island. Cities impacted by these alerts include the Philadelphia metro area, Narragansett, Westerly, Newport, and New Shoreham.In New Jersey, the southwestern region of the state, as well as Middlesex, Mercer, Monmouth, Ocean, Bergen, Passaic, Hudson, Essex, and Union counties are affected.What People Are SayingAccuWeather meteorologist Brandon Buckingham told Newsweek previously: “Ozone is a secondary pollutant, meaning it’s not emitted directly from sources, but is formed through chemical reactions. These reactions require sunlight and higher temperatures, making warmer months more prone to ozone formation. When air is stagnant, pollutants don’t get dispersed, allowing ozone to build up to unhealthy levels.”Ozone pollution is often more severe in urban areas where there are higher concentrations of pollutants from sources like cars, power plants, and industrial activities.”Jonathan Grigg, professor of pediatric respiratory and environmental medicine at Queen Mary, University of London, told Newsweek previously that there are”very clear links” between inhaling particles and earlier death from both respiratory and cardiovascular diseases.He added: “There are vulnerable groups and classically they are children because they’ve got an extra issue to do with their lungs developing, whereas our lungs are not developing as adults.”What Happens NextThe current air quality alerts are currently set to remain in effect until 11 p.m. on Wednesday.The NWS issues regular forecast updates on its website.