When produce contaminated by E. coli, Salmonella or other human pathogens is distributed by large shippers, food scares show up on the front pages and the evening news. While food safety problems in local food systems are less likely to make the national news, people can still be made ill or in rare cases killed, and the impact on a farm can be financially and emotionally devastating.
In 2006 the Center for Disease Control Disease Outbreak Surveillance System reported 1,247 disease outbreaks of foodborne illness with a total of 25,659 individual cases. Of these, 820 were of biological origin and 64 were of chemical origin, with the rest undetermined. Seven deaths were reported that year. While this is a small number compared to the 13,491 automobile deaths in 2006, there were many hospitalizations, and the impacts on individual families and businesses were severe. In 2004 produce related outbreaks surpassed those linked to beef, poultry or fish. This highlights the importance of following safe handling practices to protect the health of our families, friends and customers.
E. coli happens – What can be done?
Most strains of Escherichia coli are non-pathogenic. However, there are some strains (i.e. E. coli 0157:H7) that can cause cramps, diarrhea or severe illness such as haemolytic uremic syndrome which can lead to kidney failure. E. coli is used as an indicator of fecal contamination because it is easy to find in lab tests. OSU Extension Publication EM 8838 describes Good Agricultural Practices (GAPs) for promoting food safety on berries. The pre-harvest, harvest and postharvest practices described are relevant to all fresh produce. Mark Daeschel leads OSU Extension’s work addressing microbial food safety issues; he investigates natural products that combat pathogens. Mark and his colleagues also provide periodic food safety and food processing workshops.
Currently no food safety licenses are required to sell fresh fruit and vegetables from your own farm in Oregon. Processed products, eggs, dairy products, meat, honey and other commodities do require licenses. The Oregon Department of Agriculture (ODA) website explains what licenses are required. The ODA offers voluntary Good Agricultural and Good Handling Practices Certification for fresh fruit and vegetable growers and handlers. These audits are based on the Food and Drug Administration's Guidelines to Minimize Microbial Contamination for Fresh Fruits and Vegetables. This service aims to give the producers and consumers the confidence that Oregon grown produce is grown and handled in a manner that reduces the potential of microbial contamination.
When assessing the risk of contamination on your farm it is important to protect food safety from seed to fork. Concern arises when there is potential for the edible portion of a crop to come into contact with human or animal feces, pesticides or fertilizers. Fecal contamination can occur when raw or inadequately processed manure is improperly used as fertilizer, when contaminated irrigation water is used without proper precautions, or when workers practice poor hygiene during harvest.
National Organic Standards (NOS) require 90-120 day pre-harvest intervals for the application of raw manure and set rules for composting and manure processing that reduces pathogens. Non-certified growers are not required to follow these practices, but could consider them guidelines. Pesticides should be used only in strict compliance with label requirements. Poor manure management in a watershed or proximity to a large Confined Animal Feeding Operation can increase the risk of fecal contamination of irrigation water. When contamination is suspected water can be tested for E. coli, an indicator of fecal contamination. If results are positive, alternative irrigation water could be used, drip irrigation and micro-sprinklers may also reduce the number of pathogens on the harvested crop. Special care should be taken when irrigation is used close to harvest During harvest it is important to make sure workers have access to clean water and toilet facilities, and that they practice good hygiene.
After harvest, removal of soil from the crop dramatically reduces the pathogen load. Rapid cooling of the produce by harvesting early in the morning, hydro-cooling with clean water, forced cold air and/ or quickly transferring produce into a cold store can prevent small pathogen populations from increasing. Sanitation of the produce (i.e. with clean, chlorinated water) and sanitation of all food contact surfaces while crops are being prepared for market will reduce risk. Excellent worker hygiene during post-harvest handling is critical to prevent re-contamination and proper storage will slow reproduction of any small pathogen populations. Growth in the sale of ready-to-eat products such as bagged salad mixes and fresh berries may increase the risk of infection.
In response to the 2006 Escherichia coli O157:H7 outbreak on spinach that sickened at least 204 people, caused three deaths and disrupted the entire spinach industry in California, a voluntary Leafy Greens Marketing Agreement was developed by The Western Growers Association. Many produce distributors adopted these guidelines, effectively making them rules in the market place that are now been implemented by nearly 100% of California producers. The Agreement includes many pre-harvest and post-harvest hygiene standards. However, some required field practices restrict the use of organic amendments and have been criticized as undermining soil conservation practices.
The June 13, 2008 version of the Agreement discourages the use of raw manure, and requires a one year interval between application and planting of leafy greens. Under the Agreement, manure-derived compost and processed manure must meet standards similar to those in the NOS. Additionally, pathogen testing is required, and processed manures “should not be applied after crop emergence”, a 45 day preharvest interval is also stipulated. Other natural amendments containing animal products such as compost tea, fish emulsion, fish meal, blood meal and other bio-fertilizers must undergo heat treatment (minimum temperature: 300°F for 60 minutes resulting in a moisture content <30% dry weight) and pathogen testing.
Practices that eliminate or reduce intrusion by wildlife and livestock viewed as vectors of human pathogens are also required under the Agreement. Priority animals are deer, wild or domestic pigs, cattle, goats and sheep. Livestock cattle are the largest reservoir of E. coli 0157:H7 with up to 50% of a herd shedding the strain. By comparison, less than 1% of wildlife associated with natural environments have been found to carry it (Stuart personal communication). Monitoring for evidence of feeding, footprints, signs of feces, etc. is required and remedial actions and/or crop destruction as dictated by a food safety professional must occur when these signs are found. Commonly applied remediation tactics include removal of ponds, duck habitat, irrigation reuse systems, non-crop vegetation such as grassed waterways, filter strips, trees and shrubs. Growers report being required to use bare ground buffers, increased fencing, trapping and poisoned bait stations to kill and repel wildlife and livestock. Crops have been rejected because deer tracks were found near a field, when fields contained potential frog habitat, and portions of fields were rejected due to signs of snails, frogs, tadpoles, mice and other small animals (Beretti and Stuart, 2008). Stuart et al. (2006) point out the conflict between preharvest food safety guidelines in standards such as the Agreement and decades old efforts to improve conservation of natural resources. They reviewed the science behind pre-harvest food safety practices and argue that environmental conservation practices could actually improve food safety.
The US food supply is widely touted as the safest in the world. However as food scares on other crops arise and pressure to implement laws based on this Agreement mounts, there is a growing concern that these rules will be more widely implemented. On October 10th, 2007, the USDA announced they were considering implementing National Leafy Greens Handling Regulations. The public comment period is over, but no decision has been announced. From the text of the California Agreement it seems apparent that the authors are aware that some of the standards may conflict with soil, water and wildlife conservation practices, for example, the standards advise growers to check that food safety remediation efforts do not violate conservation laws. Nevertheless, implementation of the Agreement may increase pesticide and nutrient runoff and leaching, erosion, and degradation of aquatic and marine ecosystems (Beretti and Stuart 2008, Stuart et al. 2006). In 2003 Oregon Tilth hosted a National Summit on Human Pathogens from Livestock Manure (Scheuerell et al. 2004) to review the science of pathogen reduction in the field and discuss grower’s concerns that the NOS standards contradicted their soil building efforts. As additional research is conducted, continued dialog that can impact future rule making that balances and finds common ground between pathogen management and the soil building efforts and environmental goals of growers would be valuable. Such research and dialog would improve our chances of reaching Stuart et al’s goal of safe food and a healthy environment.
- Beretti, M. and D. Stuart (2008). Food safety and environmental quality impose conflicting demands on Central Coast growers. California Agriculture 62(2): 68-73.
- Bower, C.K., S. Stan, M. Daeschel, and Y. Zhao (2003). Promoting the Safety of Northwest Fresh and Processed Berries. OSU Extension Publication EM 8838.
- Commodity Specific Food Safety Guidelines For The Production And Harvest Of Lettuce And Leafy Greens (2008).
- Food and Drug Administration (1998). Guide to Minimize Microbial Contamination for Fresh Fruits and Vegetables.
- Scheuerell, SJ, Cuyler, A and N Andrews (2004). Pathogens, Manure and Composting. Biocycle 45(2): 38-42.
- Stuart, Shennan and Brown (2006). Food Safety versus Environmental Protection on the Central California Coast: Exploring the Science Behind an Apparent Conflict. Research Brief #10. The Center for Agroecology and Sustainable Food Systems.