Smoke from Canada and West Coast wildfires swirled across the US this week, moving east and southwards to cover skies in a thick grey haze.
Health alerts were triggered from Toronto to Philadelphia as air quality remained in the unhealthy range across much of the East Coast, reported the New York Times.
More than 80 large fires were blazing across America, and many more in Canada.
Southern Oregon’s Bootleg Fire is the largest so far in the US this year. It has already burned more 530 square miles of forest and grasslands, and is so extreme, it’s generated its own weather and triggered lightning strikes.
A series of record-breaking heatwaves and droughts linked to climate change has exacerbated the wildfires, which have now grown to such an extent that the effects are being felt thousands of miles away.
In Toronto, New York and Philadelphia on Tuesday air pollution was in the Environmental Protection Agency’s “unhealthy range” for most of the day. Cities in Minnesota recorded “hazardous” levels of pollution from the smoke travelling over the border from Canadian fires.
The National Oceanic and Atmospheric Administration posted satellite footage on Twitter, showing how the smoke had swept across North America last week.
Fine particulate matter released during wildfires is dangerous to breathe in, and can increase the risk of asthma attacks, heart attacks and strokes, reported the NYT.
Róisín Commane, an atmospheric scientist at Columbia University said that people should avoid going outdoors in high-pollution conditions, and especially avoid strenuous exercise. She also said that wearing filtered masks can give some protection for those who can’t avoid going outdoors.
“A lot of the masks people have been wearing for Covid are designed to capture PM2.5 [dangerous microscopic air pollution],” she said. “That’s the right size to be very useful for air quality.”