Smoke From California Wildfires Is Contaminating Denver’s Air

(Bloomberg) -- Hundreds of wildfires burning in California are blasting smoke over the Rocky Mountains and into Colorado, making Denver’s already poor air quality even worse.

The smoke, moving clockwise from California across the U.S. West, is affecting other states, too, extending all the way to the East Coast. But Denver was already seriously out-of-compliance with federal air quality standards, in part because its signature 300 days of sunshine help facilitate the transformation of man-made pollutants into ground-level ozone. Haze has shrouded the city’s skyline for days, prompting government warnings to stay inside.

“Our air quality is bad already — without the wildfires,” said Frank Flocke, a scientist at the National Center for Atmospheric Research in Boulder, Colorado. But the smoke is exacerbating the problem and introducing harmful particulates that can lodge in the lungs.

August ozone levels are the highest since a rash of deadly fires in 2018 in northern California -- averaging 90 parts per billion in Denver over eight hours, said Scott Landes, chief air quality meteorologist for the Colorado Department of Public Health and Environment. The federal limit is 70. A typical high ozone day in Denver would range from 70-75 parts per billion, Landes said. 

But smoke particulates pose a more immediate health risk. "You can escape ozone by staying indoors," Landes said. "Particulates can get in the tiniest cracks in windows and doors."

Colorado is in the middle of its own wildfire season, with blazes having scorched nearly 200,000 acres from one side of the Rockies to the other. But much of that smoke settles in valleys around the mountains and doesn’t reach the Denver-Boulder region, Flocke said. 

Instead, smoke from California fires is being funneled around the same high-pressure dome that’s responsible for the heat wave gripping the West -- blanketing parts of Idaho, Montana and the East Coast. 

That high-pressure system is expected to break down starting Thursday, according to Flocke. That would bring some relief to Colorado, but it could result in more smoke heading into Arizona. 

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