People watch smoke rising from a distant wildfire on Monday in Lake Forest, Calif. (Jae C. Hong/AP)

The destructive wildfires that continue to burn thousands of acres across California have created an air pollution nightmare for millions of residents on the West Coast. Smoke pouring from 20 active wildfires has prompted officials to issue air-quality alerts in several states.

As news broke Monday night that the Mendocino Complex fire has officially become the largest wildfire in California  history, residents in nearby Sacramento County were warned to stay indoors if possible through Friday.

The wildfires are emitting vast amounts of smoke full of a toxic mixture of gases and fine particles that come from burning wood and plant material. When inhaled, the microscopic particles can quickly move to the lungs and bloodstream, increasing the risk of developing asthma and other respiratory problems.

In addition to the dangerous particulate matter, the toxic combination of gases in smoke clouds provide a perfect breeding ground for the formation of surface-based ozone, which can result in negative health effects in its own right.

The view from California’s Lick Observatory, about an hour east of San Jose, was completely obscured by smoke early Tuesday.


The view from Lick Observatory, Calif., on Sunday and Tuesday. ( National Weather Service )

Weeks of wildfires combined with record-breaking heat have created a rather stagnant air mass, incapable of “mixing out” the clouds of smoke, allowing the amount of smoke to continue to increase across much of the Western United States, resulting in some historically high bad air quality.

In many areas Tuesday, the air quality reached Code Orange levels, translating to unhealthy conditions for sensitive groups such as young children, older adults and those with respiratory problems. But there were also sizable pockets of Code Red and even Code Purple conditions, meaning unhealthy to very unhealthy air for all populations.


Air-quality index at 10 a.m. Pacific on Tuesday. (AirNow.gov)

On Monday, instruments measured above 500 micrograms of particulate matter in parts of southern Oregon. “That’s about as bad as it will ever get in Beijing on a very polluted day,” said Ryan Stauffer, a postdoctoral fellow at NASA’s Goddard Space Flight Center. “You really don’t want to be outside in those conditions.”

The weather this week will only worsen air quality. An area of high pressure at high altitudes remains anchored over the Southwest, holding the hot, stagnant air in place. Meanwhile, persistent winds from the north will probably push large pockets of smoke toward Sacramento and San Francisco over the next few days, exposing millions to several days of unhealthy air quality.

“As long as the fires keep raging, there will be air-quality problems,” Stauffer said. “It will depend on where the smoke is transported, but looks like the same areas will continue to suffer for some time.”

With experts now estimating that the Mendocino Complex fire could burn for the rest of August, the air-quality woes are only just beginning.