Wildfires can XDY Exchangerelease and spread a toxic, cancer-causing chemical, new research released Tuesday finds. Known as chromium 6, it is the same toxin made infamous in the 2000 film "Erin Brockovich."

The new study, published in the British journal Nature Communications, also gives new insight into why exposure from wildfire smoke is more hazardous than pollution from other sources.

“Our study suggests far more attention should be paid to wildfire-modified chromium, and we presume additional metals as well, to more thoroughly characterize the overall threats wildfires pose to human health,” said study lead author Alandra Lopez, a postdoctoral scholar at the Stanford Doerr School of Sustainability, in a statement.

What's in wildfire smoke?

Wildfire smoke is a mix of gases and fine particles that can cause harm in multiple ways, according to the Centers for Disease Control and Prevention.

Other studies have shown a link between wildfire exposure and increased risk of death, respiratory illnesses and cancer. But this is the first one looks at the specific impact of chromium.

“In the complex mixture of gasses and particles that wildfires spew out as smoke and leave behind as dust, heavy metals such as chromium have largely been overlooked,” said senior study author Scott Fendorf, also of the Stanford Doerr School of Sustainability.

What is chromium 6?

Chromium is a carcinogenic heavy metal. According to the Environmental Protection Agency, it "exists in multiple states, but two forms are most important from a biological and health perspective – hexavalent chromium (also known as chromium 6) and trivalent chromium (also known as chromium 3)."

Chromium 6 is a known human carcinogen when inhaled and has been shown to cause tumors in mice and rats when ingested in drinking water. Erin Brockovich's battle against Pacific Gas & Electric for polluting the water supply of a small California town with chromium 6 was made well-known by Julia Roberts in the 2000 film "Erin Brockovich."

More:What does wildfire smoke do to your lungs? Here's what to know about health effects

What do wildfires have to do with chromium 6?

In the study, researchers analyzed soils and ash produced from the 2019 and 2020 wildfires across northern California, such as Sonoma, Napa, and Lake Counties. They found dangerous levels of chromium 6 in wildfire ash, which is easily blown long distances by wind.

"We demonstrate that high temperatures during California wildfires catalyzed widespread transformation of chromium to its carcinogenic form in soil and ash," the study authors wrote.

Fendorf warned that "while chromium is one of the metals of highest concern, we’re sure it’s not the only one.”

According to the study, wildfires are expected to increase in frequency and severity in many areas due to climate change, which represents "a rising public health risk from smoke and dust inhalation." The authors also suggest that metals in post-fire dust emissions may also be an increasing threat.