Despite the efforts of more than 8,000 firefighters battling against 22 major fires statewide, California's most recent natural disaster shows no signs of abating. Since Sunday night, more than 170,000 acres have gone up in flames, at least 3,500 structures destroyed, and some 20,000 people evacuated. As of Wednesday evening, only 10 percent or less of the major fires had been contained.

With so much burning, the air quality index of regions near the fires has jumped to levels never before recorded. In Napa and Sonoma counties, where flames have scorched tens of thousands of acres, levels for particulate matter have routinely surpassed 200. At this level, not only are the infirm and young at risk, but anyone outside breathing the air could suffer serious health effects.

"If there’s smoke in the atmosphere, it affects the whole body," Sarah Henderson, professor of public health at the University of British Columbia, told The Verge. "The basic message is that forest fire smoke is not good for you."

Thermal imagery of California wildfires Thermal imagery captured by the the Suomi NPP satellite of the wildfires on Oct. 9. The blazes have since burned more than 170,000 acres. (Photo: NOAA)

In the San Francisco Bay Area, where officials recently took the unprecedented step of extending a three-day-old smoke health advisory through Sunday, the haze from the wildfires has been so bad that schools have closed, flights have been cancelled, and residents are being encouraged to wear N95-rated face masks. As you can see in the time lapse below, the smoke has even managed to choke San Francisco Bay.

According to Sean Raffuse, an air-quality analyst at Crocker Nuclear Laboratory at University of California in Davis, California's wildfires have injected as much pollution into the air in two days as all the vehicles in the state produce in a year. The levels are so high that they are often equaling or exceeding air pollution indexes in Beijing, one of the world's most polluted cities.

"These fires are bringing Beijing to the Bay Area and are allowing us to see what they experience around the clock," says Richard Muller, a UC Berkeley professor of physics, told SFGate.

The choking conditions are expected to continue at least through the weekend for much of the affected area.

"Due to active wildfires and changing wind patterns, air quality could be impacted for many days to come," Bay Area officials said in a statement. "Outside of the active fire areas, air quality will be variable and unpredictable. Air quality may improve at times or get worse, very quickly."

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.