UCCE Sonoma County
University of California
UCCE Sonoma County

Produce Safety after Urban Wildfire


urban produce safety


Urban Wildfire and Potential Contamination

The fires that spread through Northern California in October 2017 burned over 160,000 acres of wildland, suburban, urban and industrial areas, creating dangerous air quality conditions for the region that lasted long beyond the fires themselves. The wildfire smoke likely included high concentrations of toxic air contaminants.[1] Following the fires, the Food and Drug Administration wrote a letter to the California Department of Food and Agriculture and the California Department of Public Health, stating that “toxic elements, firefighting chemicals, and combustion products such as polycyclic aromatic hydrocarbons (PAHs) and dioxins are of greatest concern.” There are well-known human health impacts from the inhalation of these contaminants. Additionally, plants have the potential to absorb air pollutants directly through their leaves,[2],[3],[4] but little research has been done on the risk to human health from ingesting contaminants from smoke and ash on produce grown near a burn site.

Impact on Local Farms and Gardens

Local farms and gardens played a significant role in food relief efforts immediately following the fires, contributing produce to shelters and kitchens. Many farmers, gardeners, and community members have been concerned about how the fire-related air pollution might impact locally-grown produce. Farmers have been unsure of the potential health impacts of the fire on themselves, their workers, and their consumers. School gardens, community gardens, and home gardeners have been concerned about the potential health impact on children and other vulnerable groups.

Citizen Science Initiative

In the weeks following the Sonoma County fires, concerned community members came together to launch the Produce Safety after Urban Wildfire Citizen Science Initiative. Sonoma County residents and members of the UC Master Gardener Program of Sonoma County collaborated to take samples from over 25 sites across the region using a sampling protocol created under advisement by Environmental Health and Food Safety Specialists. Samples included washed and unwashed produce, each in triplicate, to determine if contaminants are present and whether contaminants can be easily washed off produce. Volunteers focused on leafy greens with large surface area directly exposed to air pollution: kale, collards, chard, and lettuce. In total, over 200 samples were taken and frozen for subsequent laboratory analysis.

Soil contamination is also a concern for the community. Community-led soil sampling will be initiated in June 2018 to test for persistent chemicals at 7 months following the fires.



June 2018 Preliminary Report

We will post updates and reports in this section as they become available. 



Thank you to all the volunteers who are contributing time and resources to this community research initiative at this sensitive time, and to all the farms and community gardens who have had produce from their sites tested. As a citizen science project, this study depends on you, and in return, we are committed to staying in touch with you about the results from this study and next steps we can take as a community.

There are a number of ways to get involved, share resources, and to stay connected:




Our Citizen Science project is still seeking research advisors and collaborators to study the impact of the North Bay fire on the food safety of local produce, from a cumulative health perspective. We are seeking collaborators with substantial experience in their fields who can weigh in as advisors, as well as graduate students and researchers who can lend substantial capacity- such as long-term collaboration for publications and thesis or dissertation work.


Above all: we are seeking researchers with a desire to research these questions in a holistic way that understands the value of local growers for a resilient economy, takes into account the health benefits of accessing fresh produce and the larger context of chemical contamination of the mainstream food system, and prioritizes collaboration with local community.

 If you have these or other skills and have capacity to lend, please contact us at menright@ucdavis.edu


[1] Lemieux, Paul M. "Emissions of Organic Air Toxics from Open Burning." Washington, DC, United States Environmental Protection Agency 62 (2002).

[2] Uzu, Gaëlle, et al. "Foliar lead uptake by lettuce exposed to atmospheric fallouts." Environmental Science & Technology44.3 (2010): 1036-1042.

[3] Kipopoulou, A. M., E. Manoli, and C. Samara. "Bioconcentration of polycyclic aromatic hydrocarbons in vegetables grown in an industrial area." Environmental pollution 106.3 (1999): 369-380.

[4] Schreck, Eva, et al. "Metal and metalloid foliar uptake by various plant species exposed to atmospheric industrial fallout: mechanisms involved for lead." Science of the Total Environment 427 (2012): 253-262.

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