In a paper presented at the 2010 Alltech Symposium, Dr. Simon M. Shane reviewed incidents of dioxin and PCB contamination of the food chain together with appropriate measures to prevent untoward events which have profound economic and marketing consequences.


These compounds represent a related group of dibenzo-dioxins and furans have a long biological half-life extending for up to 20 years in humans and bioaccumulation in adipose (fat) tissue. Dioxins originate from volcanic activity and natural clays are frequently contaminated.

In addition, various manufacturing processes including smelting of metal ores, bleaching paper with chlorine, incineration of industrial and domestic waste and synthesis of herbicides may all contribute to the production of dioxins which can enter the food chain. Illegal or negligent disposal of hazardous wastes can contaminate soil and waterways.

Documented dioxin contamination incidents are shown in Table 1. A typical event leading to wide-scale recall of meat, eggs and milk occurred in Belgium and adjoining countries in 1999.

A small quantity of industrial oil was negligently introduced into recycled vegetable oil. Incorporating the contaminated ingredient into dairy, poultry and livestock feeds resulted in disruption of food distribution and extreme losses to producers. Regulators were tardy in their response and the impacts included the fall of the government of Belgium and widespread rejection of food products.

Dioxin incidents can be prevented by following basic precautions:

  • Never incorporate natural clays or zeolites in feeds as anti-caking agents, mycotoxin binders or fillers.
  • Evaluate the ingredient supply chain to ensure that vendors can offer traceability and certify purity using appropriate analytical technology.
  • Purchase ingredients and additives from reputable suppliers and manufacturers applying GMPs, HACCP, ISO or equivalent.  


Polychlorinated biphenyls are a diverse group of compounds which are extremely stable and persist in the environment. PCBs are responsible for severe metabolic dysfunction when consumed in large quantities over a short period. The long-term effects of chronic ingestion of PCBs include reproductive dysfunction, cognitive impairment, immunosuppression and carcinogenicity.

Virtually all PCBs are derived from chemical manufacture with over 1.5 million tons of PCBs produced worldwide since 1930. PCB compounds were used extensively in transformers, hydraulic fluids, plasticizers in paints and fire retardants before production was banned in 1979.


PCBs can be destroyed by commercial incineration in special plants achieving temperatures of 1,200ºF in the presence of oxygen. Attempts at incineration at low temperature unfortunately results in degradation compounds which are even more toxic than the commercially synthesized PCB compounds.

A list of PCB and PBB contamination incidents is shown in Table 2. Contamination of the feed chain with PCBs and PBBs involve careful evaluation of the source of ingredients especially animal proteins and ensuring traceability and purity of products. A recent source of PCB was discovered when copper sulfate obtained from Asia was subjected to analysis. PCB contamination was derived from the plastic insulation during recycling of copper wire in primitive plants producing copper sulfate feed supplement. Applying inductively coupled plasma mass spectrometry, scientists at Alltech Inc. have demonstrated heavy metal contamination including lead, arsenic, mercury and cadmium in inorganic minerals intended for incorporation in feeds (Table 3).

Cost of contamination

The financial impact of a dioxin or PCB incident can be extensive involving the value of flocks or herds which must be disposed of, decontamination, testing, recall of the product from the market, loss of export opportunities, public relations, legal costs and claims and erosion of brand image and consumer loyalty.

It is estimated that a dioxin incident involving an egg production enterprise with 5 million hens would cost in excess of $30 million. A broiler enterprise producing 3 million broilers per week or 2% of U.S. production would exceed $85 million.

Dioxin and PCB incidents are expensive. Prevention demands careful selection of suppliers offering quality control and traceability. The quality and safety of animal proteins should always be questioned.

A new range of protein supplements derived from yeast fermentation and hydroponic cultivation of algae may serve as substitutes especially for neonatal diets. Bioplex minerals will be free of organic contaminants and in addition contribute to enhanced growth which offsets the additional cost over inorganic compounds of questionable origin. Natural clays should be avoided as dietary additives.