Wildfires unleash cancer-causing chemicals from the soil, new study reveals
Wildfires can release cancer-causing airborne particles by converting naturally occurring soil metals, as revealed by recent research
New research suggests that the intense heat from wildfires has the potential to convert natural soil metals into cancer-causing particles that can be dispersed into the air. Although there is a considerable amount of research on the effects of wildfire emissions, the impact on the natural metals in soil and plants has not received as much scrutiny.
The intense heat of wildfires can cause chromium, a typically harmless metal, to become toxic airborne particles, posing a health risk to firefighters and nearby residents, as revealed in a recent study published in Nature Communications. "In the array of gases and particles released by wildfires as smoke and settling as dust, heavy metals like chromium have been widely ignored," explained Scott Fendorf, co-author of the study and professor at the Stanford Doerr School of Sustainability, in a press release.
Chromium is abundant in the soils of the western United States, Australia, Brazil, Europe, Indonesia, and South Africa.
Some natural chemical processes can convert the metal from its harmless form, known as chromium 3, into a carcinogenic substance called hexavalent chromium, or chromium 6. This toxin, made famous by the 2000 film "Erin Brockovich," can lead to cancer, organ damage, and various other health problems.
After discovering in 2019 that intense wildfire heat may trigger this process, Stanford scientists decided to investigate further. They collected samples from the chromium-rich soils of four ecological preserves in Californias North Coast Range, which had been affected by wildfires in 2019 and 2020.
The McBride Fire burns in the heart of the village in Ruidoso, New Mexico, United States, April 12, 2022. Picture taken April 12, 2022.
Ivan Pierre Aguirre/USA Today/Reuters
According to a congressional report, wildfires in the US are severely impacting real estate and homeownership. Soil testing revealed that in areas with intense and prolonged fires, toxic chromium levels were about seven times higher compared to unburned areas.
Even once a fire is fully contained, the study discovered that nearby communities to the downwind could still face exposure, as strong winds carry chromium-laced soil particles. Fendorf noted that the health risks often decrease after the initial heavy rainfall washes away the metals. However, with the ongoing impact of climate change leading to more frequent and prolonged droughts, it could be weeks or even months before rain arrives to mitigate the risk.
During the time the samples were collected, California was facing a severe, prolonged drought. The lack of rain prevented the contaminants from being washed away, resulting in the toxic chromium remaining in the soil. This persistent presence continues to threaten the health of communities nearby. Tarik Benmarhnia, a climate change epidemiologist at Scripps Institution of Oceanography, emphasized the importance of these new findings as evidence of the ongoing health risks.
Benmarhnia, who was not part of the study, stated that this explanation of metal composition adds to our current knowledge and will help us better understand the health effects on human populations. The research contributes to increasing evidence of the harmful impact of wildfire smoke, which contains fine particulate matter known as PM 2.5. When inhaled, PM 2.5 can penetrate deep into lung tissue and even enter the bloodstream, leading to various health issues such as asthma, heart disease, chronic bronchitis, and other respiratory illnesses.
Fendorf explained to CNN that their work aims to increase awareness of the toxins present in wildfire smoke. Furthermore, the researchers believe that metals such as manganese, nickel, and iron nanoparticulates may also pose similar dangers, but further study is necessary.
Wildfires play a crucial role in the ecosystem by replenishing soil nutrients and clearing away decaying vegetation. However, with the escalating climate crisis, prolonged droughts and extreme heat are causing wildfires to spread further and last longer. According to a recent UN report, the frequency of extreme wildfires is projected to rise by 30% by 2050, despite significant efforts to reduce greenhouse gas emissions.
"We anticipate more extreme weather events in the future, leading to more frequent and severe fires," Fendorf explained. "This concerning trend exposes us to higher levels of smoke and dust, which is far from ideal."
