For most of history Escherichia coli (E. coli) wasn’t considered a problem. Then, in the 1980s undercooked hamburgers, unpasteurized apple cider, and raw ground meat started making people sick, some deathly sick. There have since been thousands, maybe millions, of outbreaks around the world, all involving undercooked, unpasteurized, or raw foods contaminated with E. coli.
E. coli occurs naturally in the intestines of animals. Tim Sly, an epidemiologist and professor of public health at Ryerson University in Toronto says that “when intestinal contents are used as nitrogen sources, we need to make doubly certain that the fruits and vegetables, grown in and on that soil are very carefully washed OR properly cooked.” He claims that the use of organic growing methods is more dangerous to consumers.
Unfortunately, Sly is not alone in making this argument which is impacting the confidence of consumers in organic fruits and vegetables, though the evidence suggests that the use of organic practices are actually much safer than conventional.
The manure used as fertilizer in fruits and vegetables is not the issue in E. coli outbreaks. Manure applications happen when plants are young and when they are in the height of productivity and can use the nitrogen input, not directly before harvest. The farmers are not spraying manure on plants before they bring them to the market. Organic regulations will not even allow this, they require a long period between application and sale (e.g. the NOP regulation requires that 120 days between application and harvest). Studies have found that the NOP regulation of 120 days between application and harvest is safe and could even be significantly reduced.
Furthermore, farmers in organic and in conventional agriculture both use manure. Therefore, focusing criticisms of E. coli risk on organic producers is unfair. Most organic famers increase the safety of their foods by using aged and composted manure as a fertilizer. This manure is known to be safer than the slurry form which is used by many conventional farmers. The composting step may remove as much as 95% of the risks involved in manure application.
Finally, the soil science on this point is old and well documented. Manure has been used for fertilizer for centuries without an issue. This suggests that E. coli is not able to metabolize the low organic carbon availability in soil and that antagonistic interactions with indigenous soil microorganisms kill it off rather quickly.
The real dangers of E. coli are in animal products and not in vegetables. The most common cause of E. coli infection, according to the US Centers for Disease Control (CDC), are undercooked meat and contaminated milk. Furthermore weather, site, and storage conditions are the main factors for E.coli contamination and these are the same for both organic and conventional products.
The truth in all of this is that the safest food you can get is food that comes directly from the farmer. Large scale slaughterhouses and food that travels long distances and is handled by many people is the most likely to cause illness. Locally grown food promotes your health and the health of your food community.