Posts Tagged: food
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 on YouTube.
“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.
Additional resources and information shared during the webinar include:
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 on this web page. To view a past webinar recording with these research findings, click this link.
- Poultry wildfire resources from the UC Davis School of Veterinary Medicine:
- 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
[This article was first published Nov. 3, 2020]
Using vegetation barriers to reduce transmission of foodborne pathogens from livestock operations to fresh produce fields
Approximately 48 million people are sickened by foodborne illnesses leading to 128,000 hospitalizations and 3,000 deaths every year, according to the CDC estimates. A foodborne disease outbreak occurs when two or more people get the same illness from the same contaminated food or drink. Since most foodborne disease outbreaks can be traced back to contaminated fruits and vegetables, especially leafy greens, the disease burden has been a topic of concern for the agricultural industry and the public. Bacterial pathogens like Escherichia coli (E. coli), salmonella and campylobacter are among the common causes of the reported foodborne disease outbreaks.
How can we prevent foodborne pathogens from contaminating fruits and vegetables?
Before we can explore answers to the question of preventative measures, we must step back and ask a similarly important question: How do these foodborne pathogens contaminate the fresh produce to begin with? Understanding the different ways in which contamination occurs is imperative in exploring effective prevention measures and solutions.
So, how do foodborne pathogens like salmonella and E. coli get into our fruits and vegetables and why is there an increase in the observed foodborne disease outbreaks? Well, we can loosely attribute the general public's rejuvenated interest in consumption of fresh produce grown with sustainable or organic methods as a plausible explanation for the observed increase in foodborne disease outbreaks.
Integration of livestock and crop production as a sustainable farming practice has been speculated to be a significant contributor to the increasing numbers of outbreaks, with some research studies affirming the speculation. One such research study, conducted by North Carolina State University, showed that there was indeed significant transmission from animal operations to the fresh produce on sustainable farms. In general, contamination of fresh produce by foodborne pathogens can occur through multiple pathways including the following:
- Environmental sources such as contaminated runoff surface water
- Insect transmission and air transmission due to proximity of farm animals to fresh produce
- Contaminated manure and water irrigation systems
- Improper food handling
Some of these foodborne pathogens are resistant to antibiotics, which means that even a small case of food poisoning could become fatal, hence the need to find mitigation strategies against foodborne disease outbreaks. One solution that has been proposed is using vegetation barriers to reduce transmission of foodborne pathogens like E. coli and Salmonella on sustainable farms.
Use of vegetation barriers to mitigate transmission of foodborne pathogens on sustainable farms
Vegetative barriers are narrow and parallel strips of stiff and dense vegetation planted on or close to the contour of slopes or across concentrated flow areas. Vegetative barriers slow down runoff water and even filter it out to some extent. They also loosen and improve the soil, which allows for more water retention in the ground. Since foodborne pathogens like E. coli and salmonella can contaminate fresh produce through wind transmission and through runoff surface water from animal farms, planting vegetation barriers can effectively reduce flow of runoff water and act as a wind barrier that traps spray droplets from animal operations, intercepting foodborne pathogens and preventing them from reaching fresh produce farms.
A recent study from North Carolina State University showed evidence of decreased rates of contamination of fresh produce by foodborne pathogens, specifically E. coli and salmonella, from animal operations when vegetation barriers were employed. For this study, a five-layer vegetative barrier (31x49 m) was constructed between a dairy farm, a poultry farm, and a nearby fresh produce farm. Fresh produce, animal fecal excrement and environment samples were collected during the next 15 months and tested for the level of salmonella and E. coli contamination.
The NC State results showed that only 18% of the total E. coli and salmonella samples isolated were present in the fresh produce after installation of the vegetative barriers. Their results confirmed the effectiveness of using vegetative barriers to reduce foodborne pathogen transmission.
It is important to note, however, that while vegetative barriers might be a good measure for lowering transmission by wind and runoff surface water, other transmission pathways like using contaminated manure and improper food handling can still lead to contamination regardless of whether vegetative barriers are present or not. In such scenarios, other mitigation measures are vital.
UC Agriculture and Natural Resources is seeking outstanding UC students to apply for the 2021-22 Global Food Initiative Fellowship in communications and outreach. The student chosen to be UC ANR's GFI fellow will have an opportunity to apply their academic interests and skills to improve the lives of Californians and to get practical science-communications experience working with a Strategic Communications team.
The application deadline is Friday, July 2.
The UC Global Food Initiative addresses one of the critical issues of our time: how to sustainably and nutritiously feed a world population expected to reach 8 billion by 2025. For more information, see https://www.ucop.edu/global-food-initiative/index.html.
About the UC GFI Fellowship
The UC Global Food Initiative Student Fellowship Program funds student-generated research, related projects or internships that focus on food issues. All 10 UC campuses plus UC Agriculture and Natural Resources (UC ANR) and Lawrence Berkeley National Laboratory participate in the program. The fellow will receive a $3,000 stipend, paid half at the beginning and half at the end of the fellowship. (Applicants should be aware that receipt of a fellowship may affect your financial aid package; please contact your financial aid officer with any questions.)
The UC ANR GFI Fellowship in Communications/Outreach focuses on community outreach and education, specifically:
- Educating underserved communities in California through written, visual and digital communications about nutrition, food security, food waste prevention, childhood obesity prevention, and other food-related issues.
- Enlightening the public about UC ANR's impact on the above topics through multimedia communications.
The UC ANR GFI fellow will write one-pagers, blog posts, social media posts, news articles and other communications tools about nutrition and food issues. The fellow will also assist in the development of communication plans and outreach implementation plans. Working with the UC ANR Strategic Communications team, the fellow will create a project plan with milestones and a timeline and attend monthly meetings with Strategic Communications.
Excellent communication skills and enthusiasm for helping others are required. An ability to speak and write in Spanish is preferred but not required.
The fellow is expected to work on the project for an average of five to 10 hours per week throughout the 2021-22 academic year and is also expected to attend all UC systemwide activities for the GFI Fellowship program. Systemwide activities include an orientation in the fall, virtual leadership training, bi-monthly conference calls (starting in November), a spring field trip or conference, and a closing symposium and poster presentation to be held in conjunction with the California Higher Education Sustainability Conference (CHESC) in July 2022. Systemwide activity expenses arefunded by the UC Global Food Initiative above and beyond the fellowship award.
How to apply
To apply for the UC ANR GFI Fellowship in Communications/Outreach, please submit the
following items by email to firstname.lastname@example.org by July 2, 2021:
1. Cover letter stating your interest in this fellowship and a summary of your most relevant
experience, skills and/or education.
3. One to three examples of your previous communications work.
Select applicants will be asked to participate in a half-hour in-person interview between July 7 and 12, 2021. Applicants will be notified of the decision by July 14, 2021. Please direct any questions to Pam Kan-Rice at email@example.com.
Californians growing food in cities now have help understanding the food safety laws that apply to them. A free publication containing California-specific information on rules and regulations for urban farmers was recently published by the University of California Agriculture and Natural Resources.
Growing fresh fruits and vegetables in community gardens, backyards and rooftops helps provide more food for urban communities, creates jobs and teaches people about the value of healthy foods, according to Jennifer Sowerwine, lead author and UC Cooperative Extension specialist at UC Berkeley.
"There are a growing number of backyard and community producers who are scaling up to sell some of what they grow,” said Rachel Surls, UC Cooperative Extension sustainable food systems advisor based in Los Angeles County and co-author. “We hope this guide will help them navigate the regulations and learn best practices for keeping food safe for consumers."
“California Urban Agriculture Food Safety Guide” provides urban food producers with an overview of food safety laws and regulations that may impact their operations. To help minimize the risk of contamination of foods during their production and exchange, it also provides best practices, or Good Agricultural Practices (GAPs).
"People donating produce grown or gleaned from urban environments will learn what laws may apply to them, and practical steps they can follow to minimize the risk of foodborne illness from urban-produced foods,” Sowerwine said.
The 72-page guide covers fresh produce safety, urban soils safety, as well as food safety considerations for eggs, poultry and small livestock in the urban environment. The authors also point out which aspects of the Food Safety Modernization Act apply to urban farms, California laws that apply, record keeping requirements, information on working with gleaners, how to register as a community supported agriculture (CSA) organization, permitting requirements, and how to develop a food safety plan.
Urban farmers can do a food safety assessment of their own farms using a check list included in the publication.
The guide was produced by Sowerwine; Christina Oatfield, Sustainable Economies Law Center policy director; Rob Bennaton, UC Cooperative Extension urban agriculture advisor; Alda Pires, UC Cooperative Extension in the UC Davis School of Veterinary Medicine; Surls; Valerie Borel, UC Cooperative Extension program representative; and Andre Biscaro, UC Cooperative Extension agriculture and environmental issues advisor.
The publication “California Urban Agriculture Food Safety Guide: Laws and Standard Operating Procedures for Farming Safely in the City” is available for free download at https://anrcatalog.ucanr.edu/pdf/8660.pdf.
A new study by UC Davis researchers finds a low risk of contamination of foodborne pathogens on produce and meat at Northern California certified farmers markets, but still finds cause for some concern.
The study, published in the Journal of Food Protection, examined the prevalence of Salmonella on meat and produce, as well as the prevalence of generic E. coli on produce. Samples were taken from 44 certified Northern California farmers markets, including in the Sacramento region and Bay Area. Less than 2% (1.8%) of animal products sampled, including beef, pork and poultry, tested positive for Salmonella, while all produce samples tested negative. Slightly more than 30 percent (31.3%) of produce tested positive for generic E. coli. Generic E. coli is an indication of fecal contamination, but not all E. coli is harmful. This study didn't test for pathogenic E. coli.
“Based on this data, I think it's safe to consume meat and produce from farmers markets,” said lead author Alda Pires, a UC Cooperative Extension specialist and research scientist in the UC Davis School of Veterinary Medicine. “That's a low risk of contamination of foodborne pathogens, especially Salmonella.”
While the prevalence of generic E. coli may seem relatively high, the concentrations were low. Pires said that's especially so compared to previous studies of contamination at farmers markets elsewhere in the United States. The prevalence of Salmonella in meat sampled from Northern California farmers markets is also much lower than what previous studies have found in grocery stores.
Among the produce sampled, leafy greens had the highest prevalence of E. coli, followed by root vegetables.
Consumers should still be cautious
Consumers and farmers should still be aware that produce and meat were not free from contamination. Consumers need to make sure the foods they prepare from farmers markets follow the good hygiene practices recommended by Centers for Disease Control and Prevention. Consumers should also keep produce separate from meat to avoid cross-contamination.
“The study raises awareness that it's not just very large farms that can have contamination,” said co-author Michele Jay-Russell, with the Western Center for Food Safety at UC Davis. “Farmers need to pay attention to everything they're doing, from planting to storage, to avoid contamination.”
While certified farmers markets are inspected for food hygiene, microbiological quality is not explored. Smaller farms, those making less than $25,000 a year, are also exempt from certain food-safety provisions of the U.S. Food and Drug Administration's Food Safety and Modernization Act. Foodborne illness costs the U.S. economy more than $15 billion annually.
Other co-authors include James Stover, Esther Kukielka, Viktoria Haghani, Peiman Aminabadi and Thais De Melo Ramos of UC Davis. Research support came from the U.S. Department of Agriculture.