Food safety standards. There have been many claims that eating organic foods increases exposure to micro-biological contaminants. Studies investigating these claims have found no evidence to support them. It is important to realize that all organic foods must meet the same quality and safety standards applied to conventional foods. These include the CODEX General Principles of Food Hygiene and food safety programmes based on the Hazard Analysis and Critical Control Point (HACCP) system, where required by national regulations. Often, however, the standards of the individual organic certification body are even stricter.
Manure. One of the suggested sources of micro-biological contamination is manure. The use of manure is common in both conventional and organic systems, the potential for contamination is therefore applicable to both. It is well known that manure is a carrier of human pathogens, but properly treated (e.g. composted), it is both a safe form of organic fertilizer and more efficient nutrient source to crops. Furthermore, certified organic farmers are restricted from using untreated manure less than 60 days before the harvest of a crop and are inspected to make sure these standards and restrictions are met.
E. coli. Another stated source of worry is that of E.coli, especially virulent strains such as 0157:H7. The main source of human infection has been identified by the US Centre for Disease Control (CDC) through meat contaminated at slaughter. Evidence suggests that such virulent strains develop in the digestive tract of cattle mainly fed with starchy grains. Cattle fed with hay produce less than 1% the E.coli found in the faeces of those fed with grain. As organic cattle are fed with diets containing a higher proportion of hay, grass and silage, reducing the dependency on fodder sources off-farm, organic agriculture invariably reduces the potential risk of exposure.
Mycotoxins. As fungicides are not permitted anywhere in the production and processing of organic foods, concerns have been raised about contamination with mycotoxins due to moulds. If ingested in low doses over long periods of time, aflatoxins, the most toxic of these substances, can cause liver cancer. It is therefore important to have good agricultural, handling and processing practices, as required by both organic and conventional agriculture, in order to minimize the potential for mould growth. Studies have not shown that consuming organic products leads to a greater risk of mycotoxin contamination.
Post-harvest handling. Packaging, processing, transportation and storage is another point along the path that food travels where contamination could occur, but likewise, this is an argument equally relevant to both organic and conventional foods. The main aim of packaging is to ensure food is microbiologically stable for a defined period, and this is achieved by organic foods. Ingredients of non-agricultural origin are limited during processing and the use of irradiation for the control of pests and deteriorative changes is not permitted, but this does not mean they are necessarily less safe. It is important to note that irradiation itself is a technology that is not accepted by some consumer groups and organic foods therefore provide the consumer with an alternative. Although the organic label is not a health or safety claim, the way food is produced does affect its quality.
For more information, the FAO paper "Food Safety and Quality as Affected by Organic Farming" contains a more detailed discussion on this subject.
A critical review of organic food health including exposure to biological contaminants is provided by IFOAM and is presented under the shape of a list of criticisms and frequent misconceptions about organic agriculture with corresponding counter-arguments.