by After some recent intense wildfires in Northern California, scientists analyzed samples of charred soil and were disturbed by their findings: It was loaded with a carcinogenic metal called hexavalent chromium.
Scientists believe the heat from severe wildfires can transform a benign version of the metal, commonly found in California soil, into a notorious carcinogen, according to new research published Tuesday in the journal Nature Communications.
As climate change intensifies wildfires, scientists are trying to figure out how dangerous their smoke may be to human health. Investigators have found dangerous metals — from burned cars, homes and farms — in previous fires. The new finding adds a surprising twist to the growing body of research and suggests that wildfires burning in natural areas could also be pumping smoke containing a toxic metal into the atmosphere.
“I think it changes our risk analysis when we think about wildfire smoke exposure,” said Scott Fendorf, a professor of earth system science at Stanford University and an author of the study.
Climate change could increase the risk: wildfires that burn hotter and longer are more likely to turn harmless soil into carcinogenic dust and ash.
“Wildfires are more frequent due to climate change and the severity of the fires is greater,” Fendorf said. “You’re becoming more exposed and you’re exposed to materials that are going to be more toxic.”
Hexavalent chromium is a group one carcinogen, according to the International Agency for Research on Cancer, meaning it is known to cause cancer in humans. Exposure to large amounts of hexavalent chromium is associated with lung cancer, according to a toxicology review of the substance by the Environmental Protection Agency, which evaluated decades of workplace exposure of people who worked in chromium plating plants and chromate pigments.
In a study of mice exposed to hexavalent chromium in drinking water for two years, some developed tumors in the mouth, small intestine, and liver.
Hexavalent chromium is a well-known contaminant because it was the central chemical in the class-action lawsuit depicted in the film “Erin Brockovich” over chromium contamination in water in Hinkley, California, where the metal had been used to prevent corrosion in a Cooling tower. water in a natural gas compressor station.
About 600 Hinkley residents reached an initial settlement with Pacific Gas & Electric Company (PG&E) for $333 million. PG&E paid another $315 million to settle other lawsuits, according to the Associated Press.
The California Air Resources Board earlier this year approved a rule to phase out hexavalent chromium in industrial facilities, stating in a news release that “there was no known safe level of exposure.”
In its trivalent form, chromium is relatively harmless and abundant. But heat above 390 degrees Fahrenheit can catalyze chemical reactions that transform it into its most dangerous form, hexavalent chromium, according to the new study.
Researchers visited wildfire sites in California’s North Coast Range, including the 2019 Kincade Fire and the Hennessey Fire in 2020, to look for hexavalent chromium. They took soil samples at four ecological reserves right after firefighters finished fighting the fires and then returned about a year later to obtain follow-up data.
Some sampled areas had “metal-rich geologies”: trivalent chromium hot spots; others did not. The researchers collected about 38 soil cores in total from both sites that had burned and sites that had not.
They found “dangerous” levels of hexavalent chromium at sites where wildfires burned intensely in chaparral shrubs growing in areas that had relatively metal-rich “serpentine” soils, according to the study.
Areas without as much metal or where fires burned at lower intensity, such as grasslands where the fire passed quickly, had much lower hexavalent chromium tests.
Alandra Marie López, a postdoctoral fellow at Stanford’s Doerr School of Sustainability, said she spent several hours in the fields sampling arid, ashy landscapes, only to find high levels of chromium in the lab.
“That really catalyzed my concerns,” he said. “Firefighters spend hours on the landscape cleaning up burned areas.”
Researchers believe hexavalent chromium can travel in wildfire smoke, fly around as dust after a fire is out, and persist for months afterward.
More research is needed to understand the risk. Researchers are searching air samples for hexavalent chromium during wildfires and trying to predict the risk based on geology and vegetation, Fendorf said.
Serpentine rock is common in fire-prone areas along the coastal mountains that run along the Pacific coast.
For years, researchers have been concerned that wildfires were generating toxic metal pollution.
After the 2018 Camp Fire, which burned nearly 19,000 buildings, researchers found elevated levels of lead, zinc, calcium, iron and manganese in the smoke.
Some metals traveled more than 150 miles. During the fire, levels of lead, a potent neurotoxin, in Chico were about 50 times higher than average, California Air Resources Board researchers found.
“Toxics in wildfires are a tremendous concern,” said Barbara Weller, a pulmonary pathologist and toxicologist with the research division of the California Air Resources Board. “When a vehicle burns and when a house burns, potentially very different components are released compared to a wildfire where trees and grassland are burned.”
He said the board and academic researchers are trying to understand how dangerous wildfire smoke is. This finding adds a new aspect.
“Toxins will always be a health problem, whether they are produced by a natural or artificial source. “This highlights continued concern about the impacts of wildfires and climate change,” Weller said. Serpentine minerals “are found throughout California, which certainly adds to the concern.”
This article was originally published on NBCNews.com
