Robert Brown|The Western Wildfires Are Affecting People 3,000 Miles Away

Smoke traveling from the Western wildfires is Robert Brownreaching all the way across the U.S., bringing vibrant red sunsets and moon glow to the East. But it's also carrying poor air quality and harmful health effects thousands of miles away from the flames.

Large fires have been actively burning for weeks across the Western U.S. and Canada. Currently, the largest in the U.S. is the Bootleg Fire in Oregon, which has now burned more than 600 square miles of land and become so large it generates its own weather.

For days, Eastern states have been trapped in a smoky haze originating from the fires across the nation. Smoke has settled over major cities nearly 3,000 miles from the fires, including Philadelphia and New York, and even in the eastern parts of Canada.

It's the second year in a row that smoke has traveled so far into the East. The sight has become normal during wildfire season as fires have become more intense, long lasting and dangerous because of climate change.

Julie Malingowski, an emergency response meteorologist with the National Weather Service, told NPR that smoke pushed high into the atmosphere at the location of the fires is now being pushed down onto Eastern states.

"We're seeing quite a bit of smoke near the surface level across parts of the Eastern U.S.," she said.

"Normally, as smoke moves further away from the active fire, the smoke tends to disperse into higher parts of the atmosphere, so it's not as thick at the surface," Malingowski said. But she said that this time an area of high pressure is pushing that smoke down toward the surface.

Air quality warnings spread across the East

The result has been a flurry of air quality warnings across Eastern states, including Connecticut and Maryland. The warnings range from orange to red — orange meaning sensitive groups are at risk of being affected, and red meaning all people living in the area are at risk.

Long-distance-traveling particulate matter is to blame. Microscopic particles called PM2.5 have been injected into smoke high into the atmosphere and have traveled with the wind to cities far away.

At 2.5 microns, the particles are small enough to enter human lungs. They worsen respiratory conditions, including asthma and chronic obstructive pulmonary disease, and can interfere with oxygen exchange, says Sheryl Magzamen, an assistant professor of epidemiology at Colorado State University.

PM2.5 can be especially dangerous when people far away from fires don't get warned, Magzamen told NPR.

"When that smoke is associated with a local fire, our research has actually shown that there are less hospitalizations and ER visits on average because people are protecting themselves from the smoke and fire," she said. "However, if you're far away from them ... there's not that same type of warning system, because you're not in any danger because of the fire."

Malingowski says the smoke is likely to stick around as long as the fires rage and the weather stays dry.

"As long as active fires are burning and high pressure remains across the central part of the United States, many locations will at least see some reduction of visibility in their environment east of the Rockies," she said.

"Once fire activity decreases and precipitation reenters the picture for places that are receiving this reduction in visibility due to smoke, then that will help to mitigate smoke impacts," she added.

Josie Fischels is an intern on NPR's News Desk.