Could bushfires be spreading carcinogenic dust?

Embargoed until: Publicly released:

Wildfires might cause more health problems than smoke and dust inhalation, according to international researchers who say the fires also increase the abundance of toxic metals in the environment. The team analysed soils and ash produced from the 2019 and 2020 Northern California wildfires, and found dangerous levels of reactive chromium, a known carcinogen, in wildfire ash that is easily dispersed long distances by wind. Burning led to elevated levels of this reactive chromium in surface soil for up to a year post-fire, and in dry environments, this might be a long-term public health hazard for local communities and first responders, the team says.

Journal/conference: Nature Communications

Link to research (DOI): 10.1038/s41467-023-43101-9

Organisation/s: Stanford University, USA

Funder: This project was supported by Stanford University’s Vice Provost for
Graduate Education (EDGE Fellowship) (A.M.L.), Doerr School of
Sustainability (McGee Levorsen Grant) (A.M.L.), and UPS Foundation
Endowment Funds (A.M.L., S.F.). We thank the staff at Pepperwood Foundation (PP), Audubon Canyon Ranch (ACR), and the Sonoma Land
Trust (SLT) for collaboration and logistical support in performing
fieldwork at Pepperwood, Modini, and White Rock Preserves,
respectively. This work was performed in part at the University of
California Natural Reserve System, McLaughlin Natural Reserve
(MLNR) DOI: 10.21973/N3W08D. We thank our colleagues W. Flower,
A. Duncan, E. Paulus (Stanford), J. Bradbury (ACR), R. Ferrell (PP), and
C. Koehler (MLNR) for their fieldwork support, B. Melosh (USGS) for
geologic expertise at MLNR, as well as A. Gomes, M. Capetz, D. Burns,
D. Turner, and G. Li (Stanford), S. Bone (SSRL), and A. Foster and K.
Perkins (USGS) for their laboratory and analytical support. We are
grateful for feedback from R. Ferrell, M. Halbur, T. Commendant (PP),
M. Cooper (ACR), C. Koehler (MLNR), and M. Hammar (SLT) on our
manuscript pre-submission. We also appreciate discussions with Prof.
Ed Burton on the generation and threat of metals within fire impacted
soils. Use of the Stanford Synchrotron Radiation Lightsource, SLAC
National Accelerator Laboratory, is supported by the U.S. Department
of Energy, Office of Science, Office of Basic Energy Sciences under
Contract No. DE-AC02-76SF00515. The SSRL Structural Molecular
Biology Program is supported by the DOE Office of Biological and
Environmental Research, and by the National Institutes of Health,
National Institute of General Medical Sciences (P30GM133894). The
contents of this publication are solely the responsibility of the authors
and do not necessarily represent the official views of NIGMS or NIH.
Publicly available data associated with the Sonoma Vegetation
and Habitat Map was supported by NASA Grant NNX13AP69G, the
University of Maryland, and the Sonoma Vegetation Mapping and
LiDAR Program.

Media release

From: Springer Nature

Environment: Assessing the toxic metal threat of wildfires *IMAGES* 

Carcinogenic heavy metals — such as chromium — may be an underappreciated public health hazard from wildfire, according to a Nature Communications paper. The findings provide new insights into why wildfire smoke exposure may be more hazardous to humans than pollution from other sources.

Wildfires are expected to increase in frequency and severity in many geographic regions due to climate change, representing a rising public health risk from smoke and dust inhalation. Respiratory exposure to fine particulate matter (PM2.5) is particularly problematic owing to its ability to penetrate deep into the lungs. However, while well studied for urban fires, the chemical composition of wildfire particulate matter, and its compound-specific health effects, remain poorly characterized and the health threats arising from fire-altered toxic metals natural to soils and plants are unclear.

Alandra Marie Lopez and colleagues analysed soils and ash produced from the 2019 and 2020 wildfires across Northern California, such as Sonoma, Napa, and Lake Counties. They observed dangerous levels of bioavailable reactive chromium, a known carcinogen, in wildfire ash that is easily dispersed long distances by wind. This was found to be most prevalent in areas with an underlying metal-rich geology and was also increased by fire severity. The authors found that burning led to elevated levels of reactive chromium in the surface soil for up to a year post-fire. They suggest that in dry environments, this chromium may provide a long-term inhalation hazard from continual dust production and wind dispersal.

While threats from metal exposure in smoke and dust are recognised for urban fires, the findings highlight the public health hazard of wildfires to local communities and first responders. With increasing global wildfires owing to climate change, the authors suggest that metals in post-fire dust emissions may also be an increasing threat.

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