Dioxins and food: an overview by ANSES
On 4 January, evidence of dioxins in poultry and pigs was discovered on farms in Germany, which led the German authorities to issue a warning via the European Rapid Alert System for Food and Feed (RASFF). This contamination is likely due to the use of dioxin-contaminated animal feed. Deliveries of eggs and meat from farms that may have received the contaminated feed have been suspended. The French Ministry of Agriculture stated that France had not been sent any products from the contaminated farms and that the animal feed incriminated has not been sold outside of Germany.
What are dioxins?
''Dioxins' is a generic term referring to more than 200 different compounds that are formed during thermal processes, accidental (fires) or otherwise (incineration of industrial or domestic waste), and during chemical processes (plant-based pulp and paper treatment and impurities in certain herbicides). Thus, these compounds have never been intentionally produced by humans.
What are the effects of dioxins?
Knowledge of the effects of dioxins is based on results from animal studies and on epidemiological monitoring data of human populations with past exposure to much higher levels than those to which the general population is exposed today.
Effects that are carcinogenic, toxic to reproduction, or neurotoxic may occur with long-term exposure to moderate doses. All dioxins are thus potentially carcinogenic, with the Seveso (tetrachlorodibenzodioxin or TCDD) dioxin being classified as a definite carcinogen (carcinogenic, mutagenic or toxic to reproduction [CMR] group 1) by the International Agency for Research on Cancer (IARC -1997).
The critical effect of dioxins (i.e. that occurs at the lowest doses) is not carcinogenicity but disruption of the reproductive system. On the basis of this effect and by applying significant safety margins, the World Health Organisation (WHO) has defined a toxicity reference value.
The toxicity of dioxins is mainly related to their accumulation in the body over time (body burden) and not directly to the daily dose consumed. Except in the event of massive contamination of a given food, occasional exposure to a contaminated food will thus have little impact on health.
Occasional exposure to dioxins at high doses (due to accidental discharges, occupational activities, etc.) may cause dermal effects (chloracne, pigmentation of the nails and skin) and liver disorders (transient alteration of hepatic enzyme activity).
How are humans exposed to dioxins?
Dioxins remain highly stable when heated. They are poorly biodegradable and have a strong affinity for fats. These compounds therefore tend to build up in fatty tissues, especially those of animals, throughout the food chain. They are especially found in foods that are high in animal fats such as fish, shellfish, milk and dairy products and eggs. Food is the primary route of exposure for the general population (accounting for over 90% of total exposure).
In France, human exposure to these substances has declined sharply over the past decade following the introduction of European emission standards for incinerators. The dose to which the French population is now exposed is lower than the toxicity reference value (1) defined by the WHO(2) and has been reduced by a factor of 2.5 over the last four years and by a factor of 6 over ten years.
How is the risk of dioxin in foods taken into account?
Dioxin risk is assessed by comparing population exposure to the toxicity reference value.
Risks associated with these substances are managed by setting maximum levels for foodstuffs (statutory standards). If these are exceeded, as is occurring in Germany currently, the foods are considered to be unfit for consumption and their sale is prohibited, even if consuming them does not necessarily involve a health risk.
How is ANSES dealing with these compounds?
Given the importance of keeping the sources of chronic exposure to these substances under constant surveillance, ANSES has been studying them for over 10 years, assessing risks and monitoring exposures.
In 2008 the Agency reassessed the toxicity of these compounds in view of recent scientific data. It regularly updates the data on exposure of the French population drawing on studies such as the second Total Diet Study (EAT 2), which is currently being prepared for publication.
(1) A toxicity reference value is the dose of toxic substance to which an individual may be exposed over a given period of time without risk of adverse effects on his or her health.
(2) Provisional tolerable monthly intake established at 70 pg / kg body weight