Cancer-Causing Chromium Discovered in California Soil After Destructive Wildfires

Scientists recently tested soil after very hot wildfires in Northern California. They found high levels of hexavalent chromium, a metal that causes cancer. They think the extreme heat from the fires changed chromium already in the soil into this dangerous form.

The discovery was made public in a new scientific paper. It makes scientists worry more about health risks from breathing wildfire smoke. Scott Fendorf, a Stanford professor involved in the study, said this changes how they view the hazards of smoke exposure.

Fires worsened by climate change burn hotter and longer. This can turn more normal metal in soil into cancer-causing chromium pollution. Fierce fires spread this chemical far and wide in smoke or dust.

The impacted areas in California had just experienced major blazes. These included the destructive Kincade Fire in 2019 and the Hennessey Fire in 2020. Right after these fires, researchers gathered soil from 4 nature reserves. They went back for more samples months afterwards.

In total, they took about 38 soil samples from places burned severely or lightly, as well as unburned land. The results showed burning chaparral plants led to high chromium levels in nutrient-rich soil. But they found only minimal amounts where fires burned gently or not at all.