Chemical Hazard: Dioxins and PCB’s (Polychlorinated biphenyls)

Chemical Hazard: Dioxins and PCB’s (Polychlorinated biphenyls)

 

Dioxins and PCB’s (Polychlorinated biphenyls)

Dioxins are colorless, odorless organic compounds containing carbon, hydrogen, oxygen and chlorine. Dioxins are ubiquitous environmental contaminants that have been found in soil, surface water, sediment, plants and animal tissue worldwide. They are highly persistent in the environment.

PCB’s or Polychlorinated biphenyls, are chlorinated aromatic hydrocarbons and are produced by the direct chlorination of biphenyls. Like dioxins PCB’s are widespread environmental contaminants and are very persistent in soil and sediments.

Dioxins and PCB’s have a broad range of toxic and biochemical effects and some are classified as human carcinogens.

Occurrence in Foods: Dioxins and PCB’s enter the food chain through a variety of routes. Grazing animals and growing vegetables may be exposed directly or indirectly to these contaminants in the soil.

Leafy vegetables, pasture and roughage can also become contaminated through airborne transport of dioxins and PCB’s.

A significant percentage of paper food packaging materials also contain PCB’s which have the potential to migrate to the packaged food.

Extensive stores of PCB-based waste industrial oils, many with high levels of PCDFs, exist throughout the world. Long-term storage and improper disposal of this material may result in dioxin release into the environment and the contamination of human and animal food supplies.

Dioxins are mainly by-products of industrial processes but can also result from natural processes, such as volcanic eruptions and forest fires. Dioxins are unwanted by-products of a wide range of manufacturing processes including smelting, chlorine bleaching of paper pulp and the manufacturing of some herbicides and pesticides. 

 Effects on Health:

 Humans accumulate dioxins in fatty tissue mostly by eating dioxin contaminated foods. The toxicity of dioxins is related to the amount accumulated in the body during the lifetime.

Once dioxins enter the body, they last a long time because of their chemical stability and their ability to be absorbed by fat tissue, where they are then stored in the body. Their half-life in the body is estimated to be 7 to 11 years. In the environment, dioxins tend to accumulate in the food chain. The higher an animal is in the food chain, the higher the concentration of dioxins.

Short-term exposure of humans to high levels may result in skin lesions, such as chloracne and patchy darkening of the skin and altered liver function.

Dioxins and PCBs are found at low levels in many foods. Longer-term exposure to these substances has been shown to cause a range of adverse effects on the nervous, immune and endocrine systems, and impair reproductive function. They may also cause cancer. Their persistence and the fact that they accumulate in the food chain, notably in animal fat, therefore continues to cause some safety concerns

The developing foetus is the most sensitive to dioxin exposure. New-born with rapidly developing organ systems may also be more vulnerable to certain effects

Prevention and control of dioxin exposure

 Proper incineration of contaminated material is the best available method of preventing and controlling exposure to dioxins. It can also destroy PCB-based waste oils. The incineration process requires high temperatures, over 850°C. For the destruction of large amounts of contaminated material, even higher temperatures - 1000°C or more - are required.

 Prevention or reduction of human exposure is best done via source-directed measures, i.e. strict control of industrial processes to reduce formation of dioxins as much as possible. This is the responsibility of national governments. The Codex Alimentarius Commission adopted a Code of Practice for Source Directed Measures to Reduce Contamination of Foods with Chemicals (CAC/RCP 49-2001) in 2001. Later in 2006 a Code of Practice for the Prevention and Reduction of Dioxin and Dioxin-like PCB Contamination in Food and Feeds (CAC/RCP 62-2006) was adopted.

 Most of human exposure to dioxins is through the food supply, mainly meat, dairy products, fish and shellfish. Protecting the supply chain is one of the most important factors.

Food and feed contamination monitoring systems must be in place to ensure that tolerance levels are not exceeded.

Avoid those areas with increased dioxin contamination due to local emission, accidents or illegal disposal of contaminated materials that are used for grazing or for the production of feed crops. If possible, contaminated soil should be treated and detoxified or removed and stored under environmentally sound conditions.

Limits for dioxins and PCBs set out in EC regulation No. 1881/2006
Foodstuff	Maximum levels (sum of dioxins)	Maximum levels (sum of dioxins and dioxin like PCBs)
Meat from Bovine animals and Sheep	3.0 pg per g of fat	4.5 pg per g of fat
Meat from Poultry	2.0 pg per g of fat	4.0 pg per g of fat
Meat from Pigs	1.0 pg per g of fat	1.5 pg per g of fat
Muscle meat of fish and fishery products	4.0 pg per g of fat	8.0 pg per g of fat
Hen Eggs and Egg products	3.0 pg per g of fat	6.0 pg per g of fat
Vegetable oils and fats	0.75 pg per g of fat	1.5 pg per g of fat