by After several recent severe wildfires in Northern California, scientists tested samples of singed soil and were shocked by their results: It was loaded with a cancer-causing metal called hexavalent chromium.
Scientists think the heat of severe wildfires can turn a harmless version of the metal, commonly found in California soil, into an infamous carcinogen, according to new research published in the journal Nature Communications on Tuesday.
As climate change increases wildfires, scientists are trying to figure out how dangerous the smoke can be to human health. Researchers have found dangerous metals – from burnt-out cars, houses 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 may also be pumping smoke containing toxic metals into the atmosphere.
“I think it changes our risk analysis when you think about exposure to wildfire smoke,” said Scott Fendorf, professor of earth system science at Stanford University and author of the study.
Climate change may 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 because of climate change and the fires are more intense,” Fendorf said. “You’re getting more exposure and you’re going to be exposed to materials that are going to be more toxic.”
According to the International Agency for Research on Cancer, hexavalent chromium is a group one carcinogen, meaning it is known to cause cancer in humans. Exposure to large amounts of hexavalent chromium is associated with lung cancer, according to a toxicological review of the substance by the Environmental Protection Agency, which evaluated years of workplace exposures in people who worked in chrome plating and dye plants. chromate.
In a study of mice exposed to hexavalent chromium in drinking water for two years, several tumors developed in their mouths, small intestines and liver.
Hexavalent chromium is a well-known pollutant because it was the central chemical in the class action lawsuit depicted in the movie “Erin Brockovich” over chromium contamination of water in Hinkley, California, where the metal was used to prevent corrosion in the cooling tower. water at a natural gas compressor station.
About 600 Hinkley residents settled an initial case 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 successfully phased out hexavalent chromium at industrial facilities, saying 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 greater than 390 degrees Fahrenheit can catalyze chemical reactions that transform it into its more dangerous form, hexavalent chromium, the new study said.
Researchers visited wildfire sites in California’s Northern Coast Range, including the 2019 Kincade Fire and the 2020 Hennessey Fire to look for hexavalent chromium. They sampled soil in four ecological preserves immediately after firefighters finished battling the blazes, then returned about a year later for follow-up data.
Some sampled areas had “metal-rich geologies” — hot spots for trivalent chromium; others did not. The researchers collected a total of about 38 soil cores from both burned and unburned sites.
They found “dangerous” levels of hexavalent chromium levels at sites where wildfires had burned heavily in chaparral bushes growing in areas with relatively metal-rich “snake” soils, the study said.
Areas with less metal or where the fires burned at lower intensity – such as grasslands where a fire spread quickly – tested much lower for hexavalent chromium.
Alandra Marie Lopez, a postdoctoral fellow at the Stanford Doerr School of Sustainability, said she spent several hours in a field sampling a barren, ashy landscape, only to find high levels of chromium back in the lab.
“That really added to my anxiety,” she said. “Firefighters are spending hours in the landscape dousing burned areas.”
The researchers believe that hexavalent chromium can travel in wildfire smoke, be blown as dust after a fire is out and linger for months afterward.
More research is needed to understand the risk. The researchers are continuing to sample air for hexavalent chromium during wildfire events and try to predict risk based on geology and vegetation, Fendorf said.
Serpentine rock is common in fire-prone areas along the coastal mountains that run up and down the Pacific coast.
Researchers have been concerned for years that wildfires were creating toxic metal pollution.
After the Camp Fire in 2018, 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 above average, researchers from the California Airworthiness Board found.
“The toxins in wildfires are a big concern,” said Barbara Weller, a pulmonary pathologist and toxicologist in the research division of the California Air Quality Board. “When a vehicle burns and when a house burns, that one releases very different components compared to a wildfire where you’re burning trees and grass.”
She said the board and academic researchers are trying to get a handle on how dangerous wildfire smoke is. This result adds a new wrinkle.
“Toxins will always be a health concern, whether they are from a natural source or an artificially produced source. This leads to ongoing concerns about the impacts of wildfire and climate change,” Weller said. Serpentine minerals are found throughout California, and that certainly adds to the concern.”
This article was originally published on NBCNews.com
