Will California Fires Create Toxic Rain? Experts Say No—Here's Why

Experts debunked a message shared thousands of times on social media that warned of the threat of "extremely toxic" rain as a consequence of the Camp Fire in California.

The Facebook post told people not to let animals or pets out into the "toxic" rain, to wash them thoroughly if they do get out, and to keep a set of "outside" clothes and to change out of them immediately upon arriving home.

While some standing water in affected areas may contain chemicals from the ash already on the ground, there is no risk from the rain itself, which is forecast to fall over the Camp Fire area in the coming days.

"The smoke in the air will likely get largely washed out by the rain," Chris Cappa, a professor in the Department of Civil and Environmental Engineering at the University of California, Davis, told ABC 10.

"It takes it out of the atmosphere and moves it down to the ground where it runs off into our sewers and drains through your lawn," the report said.

"As bad as it is to breathe, in the end," Cappa continued, "it's not that much material in the atmosphere so when you wash it out, it's really a small one relative to everything that we have on the ground already."

A California Air Resource Board spokesperson told the fact-checking publication Snopes that emissions from the homes and other structures destroyed by the Camp Fire "have literally gone south with the prevailing winds last week.

"The smoke we are seeing now comes from vegetative matter still burning and our own anthropogenic stuff," the report continued, adding that it was unlikely that any of the rain set to fall would contain toxic particles.

The spokesperson said: "The scale of weather system producing rain usually precludes toxic pollution from being trapped within raindrops in California. Winds also dilute and push emission northeastward away from areas where the fires burned."

According to The Associated Press, the rain would help quench the Camp Fire but hinder search and recovery efforts by "washing away fragmentary remains and turning ash into a thick paste."

There was also the risk of landslides in hilly areas and cloying wet mud could make it even more difficult for search teams to reach certain areas.

Cal Fire said the Camp Fire in Butte County was 151,272 acres in size and 70 percent contained by the 4,736 personnel still battling the flames.

At least 79 people are dead, a figure likely to rise because hundreds are still missing. More than 11,700 homes have been destroyed in the fire, along with 472 commercial structures.

The firesmoke severely damaged the air quality in local areas. At its worst, the air became hazardous. It has since improved, but the air quality is still very unhealthy within the Camp Fire area, the Environmental Protection Agency's AirNow system said.

Nearby Chico, which is on the edge of the fire, has unhealthy air, as do other towns and settlements in the surrounding area of the Camp Fire.

"People with heart or lung disease, older adults and children should avoid prolonged or heavy exertion. Everyone else should reduce prolonged or heavy exertion," said the EPA's advisory.

camp fire paradise rain
Kimberly Spainhower, left, and her husband, Ryan Spainhower, weep while searching through the ashes of their burned home in Paradise, California, on November 18. The family lost a home in the same spot to a fire 10 years ago. JOSH EDELSON/AFP/Getty Images
Will California Fires Create Toxic Rain? Experts Say No—Here's Why | U.S.