Smoke from more than 100 uncontrolled wildfires burning across Ontario has spread hundreds of miles into the Midwest and Northeastern United States, creating hazardous air quality conditions in many major cities.Areas from Minnesota to New York have experienced dense haze, while Toronto saw dramatic orange skies caused by the thick smoke.The smoke contains PM2.5, extremely small airborne particles that can penetrate deep into the lungs and are associated with respiratory and cardiovascular health risks.

In New York City, the Air Quality Index (AQI) reached approximately 180, placing it in the 'unhealthy' category, while Duluth, Minnesota, exceeded an AQI of 500, a level considered hazardous for everyone.

Health experts advise people with asthma, lung disease, heart conditions, children, and older adults to minimize time outdoors during poor air quality events.

Even healthy individuals are encouraged to reduce outdoor activities when AQI levels exceed 100 and to wear properly fitted N95 respirators if extended outdoor exposure is unavoidable.Researchers also recommend avoiding strenuous exercise outdoors until conditions improve.The smoke event is occurring alongside an intense heat wave, further increasing health risks.

Scientists cited in the report emphasize that climate change is contributing to longer and more severe wildfire seasons by creating hotter and drier conditions.

Recent research estimates that wildfire smoke already contributes to tens of thousands of premature deaths annually in the United States, with that number projected to rise substantially if global warming continues.Experts also note that wildfire smoke is becoming a dominant source of air pollution, even as emissions from vehicles and power plants have declined.

They stress that public cooling centers should prioritize clean indoor air through filtration systems in addition to providing relief from extreme heat.