- Author: Jeannette E. Warnert
A summer of smoke and ash in many parts of California has raised questions about the safety of produce growing on farms and in the garden, eggs laid by chickens who peck around in ash-laden areas, and remediation needed to safely and effectively grow food in the future.
UC Agriculture and Natural Resources brought together experts who have researched the effects of previous fires' fallout and studied soil contaminants to share their insight in a two-hour webinar now available at Post-fire Soil Safety video.
“The No. 1 health concern during a fire is smoke inhalation, and it's been well documented that wildfire smoke can negatively impact both the heart and the lungs,” said Claire O'Brien, a pharmacology and toxicology doctoral student at UC Davis. “However, the chemicals found in the smoke don't just stay in the air. They can deposit onto plants and into soil and water.”
Although every fire is unique, some generalizations can be drawn from research conducted following previous fires. UC Cooperative Extension food systems advisor Julia Van Soelen Kim detailed a study conducted following the October 2017 wildfires in Sonoma County and across the North Bay.
With the help of UC Master Gardener and community volunteers, the researchers collected over 200 samples of homegrown collard greens, lettuces, kale and chard that were exposed to wildfire smoke and ash. A subset of the samples were analyzed by a private laboratory.
“There was very low concern about chemicals on produce,” Van Soelen Kim said. “No samples had detectable levels of lead, arsenic, mercury or chromium. And that's a huge sigh of relief.” However, analytical results vary by site, site history and by fire event, and few have pre-fire baseline data to compare with.
Van Soelen Kim said basic food-safety practices should be followed when preparing to eat food grown in a home garden, regardless of ash or smoke contamination.
“You should always wash your hands before and after harvesting, and wash your produce in running water to mitigate any kind of potential risk,” she said.
Are backyard chicken eggs safe to eat?
Another study outlined at the webinar used a similar process to determine whether there might be contaminants in the eggs laid by backyard poultry that live and feed in areas exposed to wildfire ash and smoke.
Scientists know from previous research that chickens exposed to lead in their environment can produce eggs with high lead content and that heavy metal content of ash from urban wildfires is higher than from rural wildfire.
“We combined those two pieces of research with what we know that chickens do all day: they peck at the ground for hours on end,” said Todd Kelman, a veterinarian in the School of Veterinary Medicine at UC Davis. “That makes for a pretty good hypothesis that urban wildfire could pose a risk for the production of eggs and poultry that contain heavy metals.”
Kelman and his team put out a call for eggs from backyard poultry and received samples from 344 premises in fire-affected and non-fire-affected areas of California.
Surprisingly, egg samples that contained higher lead levels came from parts of the state that were not directly impacted by ash and smoke.
“Did our data support our hypothesis that proximity to urban wildfire is a driving source for lead in eggs of backyard poultry? The answer is not so much,” Kelman said. “So, is it safe to eat eggs from your backyard poultry? We can't give you a definitive answer to that question. But we do suggest you assess your risk and reduce the risk of contamination.”
Practices that reduce the risk include keeping chickens off the ground, using a chicken feeder that prevents spillage onto the ground and making calcium readily available, for example in the form of oyster shells, because calcium can prevent the absorption of lead. Making sure that chickens are provided uncontaminated water is also an important part of risk reduction.
For confirmation on the safety backyard chickens and their eggs, lab tests for eggs are available for $60 from the California Animal Health and Food Safety Laboratory at UC Davis, or chickens may be submitted to CAHFS for necropsy.
Are soils safe for growing food after a fire?
Fire effects on soil is another consideration in burned areas, said UC Cooperative Extension urban agriculture advisor Rob Bennaton.
“Fires heat topsoil layers. They reduce the amount of living micro-organisms at the site of the burn, and also affect organic matter and nutrients. Ash deposits over time may make soils more alkaline,” he said. “As a result of these combined factors, there are temporary changes in nutrient levels and the capacity for soils to exchange nutrients for optimal plant growth and nutrition.”
With proper land care and management, soils can be remediated over time.
“It won't happen overnight. Soils were developed over millions of years,” he said.
Some ways to improve safety when gardening in fire-affected areas including keeping the soil covered with wood chips or other landscape mulch to reduce airborne soil dust. Use drip irrigation to prevent up splash onto the undersides of growing vegetables. Promote good drainage, especially at the bottom of slopes to prevent the concentration of contaminants.
Lab tests are often needed to determine the soils' post-fire characteristics. “Don't guess, but test,” Bennaton said.
The UC Master Gardener Program can provide technical assistance to help home gardeners find resources for home soil testing, he said.
Resources and information shared during the webinar
Post-fire soil resources and soil testing information
- UCCE publication on Soils in Urban Agriculture with soil testing & sampling information
- The UC ANR Healthy Soils Website, which has many resources worth reviewing.
- Tips for Interpreting Soil Analysis
- UC Master Gardener of Sonoma County 2018 workshop video “Effects of fire on soil”
Post-fire food safety
- Research on produce safety and backyard chicken egg safety after the 2017 wildfires in California is available at Produce Safety after Urban Wildfire. To view a past webinar recording with these research findings, visit Post-fire Food Safety.
- Poultry wildfire resources from the UC Davis School of Veterinary Medicine
- UC Davis School of Veterinary Medicine: "Safety of Backyard Chicken Eggs Post Wildfire" video
- Best Practices for Produce Safety After Fire
- Understanding Risk: A community guide for assessing the potential health impacts of locally grown produce exposed to urban wildfire smoke
Firewise and sustainable home landscaping design in the defensible space zone
- Visit the UC Master Gardener Program of Sonoma County firewise landscaping web page.
- For a recent firewise & sustainable design and maintenance video by the Resilient Landscapes Coalition.
Impact of smoke & ash on plants
- Author: Lisa A Blecker, coordinator for the UC Pesticide Safety Education Program and Office of Pesticide Information and Coordination
- Author: Whitney Brim-DeForest, UC Cooperative Extension rice advisor in Sutter and Yuba counties
- Author: Katrina Hunter, UC Integrated Pest Management Program pesticide safety writer
- Author: Pamela Kan-Rice, UC ANR Assistant Director, News and Information Outreach
While most Californians are staying home to slow the spread of the novel coronavirus, California farmers, farmworkers and other agricultural professionals are out in the fields and packing houses working to produce food.
With increased demand for personal protective equipment, or PPE, to protect against COVID-19, these essential workers are facing shortages. Agricultural commissioners in 28 counties are hearing from farmers who are having trouble getting PPE for their employees and farmers in another 11 counties who are worried about running out of PPE in the next month or twoaccording to a California Department of Pesticide Regulation survey.
To reduce the spread of COVID-19, workers may wear homemade face coverings, but for applying pesticides, they must wear respirators specified on the pesticide product label, said Whitney Brim-DeForest, UC Cooperative Extension rice advisor.
Pesticide applicators may use gear that is more protective than required by the product label and regulations.
“Although this could change in the days ahead, half-mask and full-mask respirators are more available than disposable N95 respirators for now,” said Lisa Blecker, coordinator for the UC Pesticide Safety Education Program.
Before the pandemic, 10% of N95 respirators from 3M went to health care, but that number is now 90%, the company said in a letter to distributors. This has led to significant backorders of PPE supplies for distributors.
Carl Atwell, president of Gempler's, an online distributor of worker supplies, said that before the crisis, normal lead times for PPE was up to 10 days. He estimated disposable respirators will become available in the fall and other PPE supplies in August.
In the meantime, there is alternative PPE that agricultural professionals can use during the shortage.
Atwell suggests looking for lesser known brands of PPE as opposed to the first tier of choice: “It's sort of like searching for Purell hand sanitizer. Purell brand might be out of stock, but can you find a different disinfectant?
On Gempler's website, the more recognizable Tyvek coverall from Dupont is sold out, however disposable protective clothing is available from other brands. Reusable chemical-resistant clothing is also available as opposed to their disposable counterparts. Supplies in high demand are reusable and disposable nitrile gloves, protective clothing, disposable respirators and certain protective eyewear, such as goggles and face shields.
For workers who will be applying pesticides, Blecker and Brim-DeForest offered some guidelines on how to meet PPE requirements as the shortage continues.
General PPE requirements: “Remember, the label is the law,” said Brim-DeForest. “PPE requirements for agriculture are not being loosened.” The UCCE advisor recommends purchasing only what you need for the season and choosing reusable PPE whenever possible. Growers who have excess supplies of PPE can coordinate with their county agricultural commissioner or UCCE advisor to help other producers in their area.
Respirators: If you can't find the respirator required on the label, Blecker said, “Use an alternative, more-protective respirator. For example, if an N95 is required, you can use a half-mask with N95 particulate filters; these can be stand-alone filters or ones that attach to an organic vapor cartridge. You could also use a different pesticide that doesn't require a respirator. Consult with your PCA (pest control adviser) for options.”
Gloves: Chemical-resistant gloves, usually 14 mil or more in thickness are required for most California pesticide applications and should be worn by mixers, handlers and applicators. If nitrile gloves are not available, viton and laminate gloves are universal chemical-resistant materials for most pesticide labels. If the glove material is specified on the label, that instruction must be followed.
“Disposable gloves less than 14 mil can be worn, but not for more than 15 minutes at a time,” Blecker said. “Farmers should also note that thinner gloves cannot be layered on top of one another.”
Coveralls: Coveralls should be worn when required by the pesticide label or when the signal word is “WARNING” or “DANGER,” or when applying by backpack or airblast. “Coveralls can be made out of high-density polyethylene fibers (Tyvek and other brands), which are disposable, or cotton, which are reusable,” Brim-DeForest said. “If reusable coveralls are worn, the employer must ensure employees are provided clean coveralls.”
Goggles/face shields: Face shields are required for mixing and loading pesticides only if it's stated on the label. “If a face shield is unavailable, a full-face respirator can be used,” Blecker said. “Goggles or protective eyewear should always be worn in California when handling pesticides, regardless of what the label says. The face shield, goggles or safety glasses must provide front, side and brow protection and meet the American National Standards Institute Z87.1 standard for impact resistance.
For more information about PPE, contact your county agricultural commissioner or see the California Department of Pesticide Regulation's posters:
- Author: Julia Van Soelen Kim
Two years ago today, Sonoma County residents awoke to fire spreading through urban and wild lands across our county, a dark cloud of smoke covering the sky, and ash blanketing the ground. There continues to be much work for our community to collectively recover from the fires--most of it is hard and heavy work, whether it be emotional work, community work, economic work, environmental work. UCCE Sonoma's Produce Safety after Urban Wildfire: Citizen Science Initiative is just one small piece of that body of work.
The project sought to find out if garden and farm-grown produce exposed to ash was safe to eat, mobilized community in the days and weeks after the fire to collect leafy greens from sites across the county for later analysis, formed a unique partnership between UCCE Sonoma, Petaluma Bounty, and a passionate public health researcher, Vanessa Raditz, and ultimately led to a workshop series, a newly published scientific report, a forthcoming toolkit for other communities affected by wildfire to assess the safety of their own unique context, and a collaboration with researchers from UC Davis School of Veterinary Medicine to investigate the safety of backyard chicken eggs in fire affected counties.
Today we honor the terrible toll of the fire on this community, and we welcome your participation in our upcoming Post-Fire Food Safety Workshop as a small piece of recovery and learning for the future. The workshop will be held on Thursday, Oct. 17, 2019 from 6:00pm-8:00pm at the Environmental Center of Sonoma County, 55 Ridgway Ave., Santa Rosa, CA 95401. Refreshments will be provided. RSVP at ucanr.edu/postfirefoodsafety10.17.19
“Produce Safety After Urban Wildfire” citizen science project
The Northern California fires of October 2017 created poor air quality and distributed toxic air contaminants over the region. Following the fires and the incredible response from local farmers, UCCE Sonoma County embarked on a “Produce Safety After Urban Wildfire” citizen science project to help answer community concerns about whether the safety of local produce might have been impacted by contaminants carried in the smoke and ash from the fire.
With the support of UCCE Sonoma, community members concerned about the impact of toxic smoke on local produce and UCCE Master Gardeners took over 200 samples of leafy greens from 25 gardens and farms across Sonoma County in the immediate aftermath of the fires; in the summer of 2018 the team took soil samples from five of the original sites sampled. Using funding from University of California Agriculture & Natural Resources Division and the Bay Area Air Quality Management District, we had produce and soil samples from five sites most likely to have received deposits of toxic air contaminants from the urban wildfire tested for heavy metals, dioxins and polycyclic aromatic hydrocarbons.
Based on preliminary findings, we hypothesize that produce safety was not significantly affected by the fires and may be mitigated by washing produce. Preliminary analysis was inconclusive but did not indicate a high degree of contamination. Polycyclic aromatic hydrocarbons were inconclusive due to high method reporting limits from our laboratories. Heavy metals were of low concern, with no detection of lead, arsenic, or mercury. Nickel was found in 2 of 8 samples at levels exceeding Proposition 65's No Significant Risk Level but which may be mitigated by washing produce. Dioxins were of some concern with concentrations found above background levels from FDA's Dioxin Monitoring Program, but below NSRL.
- It is important to note that over long periods of time, exposure to these chemical groups at very low levels can still contribute to health impacts, including at levels below what our tests are able to detect.
- Numerous health benefits including cancer risk reduction have been attributed to green leafy vegetables. These benefits may outweigh the additional risk from trace contaminants detected in some produce in this study. Quantitative comparisons will be provided in our final report.
- Some individuals have higher risks and may want to be in communication with their healthcare provider to better understand if they should take extra precautions. Individuals at higher risk may also benefit greatly from the high nutrition in green leafy vegetables and fresh produce.
- Best practices for reducing risk include: wearing a respirator mask during poor air quality; washing produce thoroughly in running water; peeling root vegetables, testing soil regularly; containing and amending contaminated soil through sheet mulching, raised beds, and compost.
- Best practices that enhance protective factors and should also be pursued, such as increasing produce consumption to promote healthy nutrition, improve immunity, and support resilience to chemical exposures.
Over the next few months, we will be completing our final report and creating additional tools for communicating these results to concerned community members. In the Spring of 2019, we will be conducting community workshops. Reports, handouts, workshop materials, and the protocols from the study will be made publicly available for use by communities experiencing wildfire in the future./h3>/h3>/h3>
Local food producers: The recent wildfires are creating dangerous air pollution in our region. The biggest threat to your health is from inhaling the smoke. Protect your lungs by staying indoors whenever possible, and wearing a respirator mask when outdoors. An N95 respiratory is the minimum protection recommended, while a P100 will provide additional protection from petroleum-based chemicals and smaller particles. Employers of outdoor workers should consider adequate protection for their workers, such as limiting the time that employees work outside and providing adequate respiratory protective equipment (see California Code of Regulations Title 8 section 3203, Injury and Illness Prevention Program, and section 5141, Control of Harmful Exposure to Employees).
During the fires in Sonoma County last fall 2017, many local food growers expressed concern about the impact of the wildfire smoke on the food safety of our local produce. Since then, a group of researchers and concerned community members have been investigating this question. The Produce Safety after Urban Wildfire project will be releasing a final report in early 2019. However, due to this current air pollution emergency, we would like to share that the lab results from our
plant samples DO NOT show extensive contamination of produce exposed to wildfire smoke, and our findings suggest a low health risk from ingesting produce exposed to wildfire smoke.
Fresh produce, especially green leafy vegetables, are critical for nutrition and promoting the body's resilience to the health impacts of smoke. To further reduce risk of contamination, wash produce with running water and remove outer leaves or peels and wash hands after harvesting produce or coming in contact with soil and ash.
Some groups are more vulnerable to health impacts from the smoke and should take extra precaution during this time, including children, elders, and people with respiratory and heart conditions. If you are a garden educator working with kids, please consider activities that can be done inside until air quality improves.
We encourage our community to continue supporting our local food system and sharing our online resources with all those concerned, including our publication:
See our Produce Safety after Urban Wildfire for more resources and information.
Sign-up for our google group of community members discussing these issues and sharing strategies./span>