Chemical residues in poultry and eggs produced in free- range or organic systems

Residues in poultry arise from accidental or intended exposure to chemicals. The exposure routes are by oral ingestion (feed, water, soil and preening), by inhalation, by dermal absorption or by injection. Chemical contaminants are not a major issue in the principles of organic or free-range systems. Risk management of chemicals has not been addressed widely and if so the attention was focused on intentionally used chemicals. This paper aimed to review and identify possible contamination sources in organic or free-range production and substantiate some possibilities with available data. High levels of dioxins in eggs from organic systems have been reported from several European countries. Eggs from other outdoor systems seemed to contain lower levels. No explanation for this difference is at hand. The higher contamination in organic systems seems to be related to soil contamination and soil ingestion. Other materials like Pentachlorophenol (PCP) treated wood also constitute a risk for dioxin contamination of farm animals. Drugs residues are generally not higher in systems using litter, but due to recirculation via the litter, persistence of residues is often considerably longer.