Dioxin, PCBs and Furans

Dioxin exposure in food arises from consumption of meat and dairy products. Dioxins comprise a family of 210 compounds, of which 17 are considered toxic and virtually non-biodegradable. The most notorious, well-studied, and toxic chemical in this family is 2,3,7,8-tetrachlorodibenzo-p-dioxin, or 2,3,7,8-TCDD, commonly referred to as TCDD. TCDD is colorless and odorless. It occurs as a contaminant in the manufacturing process of certain chlorinated organic intermediates and products, such as chlorinated phenols. A combination of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-T, called Agent Orange, was used in the Vietnam War by the US military for defoliation and crop destruction. Dioxin is fat-soluble and bioaccumulates in the food chain. In areas where fish is a major source of the diet, dioxin levels can be 100,000 times that of the surrounding environment. Dioxin enters our environment from several different sources; however, the largest source of man-made contamination comes from trash incineration processes (mainly of certain plastics) and enters the food cycle when the air emissions deposit the contaminants on farmlands with livestock and crops. 

Other sources of dioxin contamination are heavy-duty diesel trucks and equipment, industrial wood combustion, EDC/VCM production, sintering plants, automobiles using leaded gasoline, land applied 2,4-D, oil-fired utilities, lightweight aggregate kilns that combust hazardous waste, petroleum refining, catalyst regeneration, cigarette smoke, boilers/industrial furnaces, crematoria, and drum reclamation.

Polychlorinated Biphenyls (PCBs) are a class of chlorinated compounds, which include 209 congeners with different physical and chemical characteristics. Food is a major source of human exposure, mainly through fish and animal fat.
PCB compounds enter the environment from sources such as oils and fluids from transformers and capacitors, poorly maintained toxic waste sites, improper disposal of PCB containing materials. They are usually found at the bottom of water sources, in the sediment. Bottom-feeders and other aquatic life forms feed within this region and accumulate the PCBs in their tissues as a result.
During 1968 in Japan, cooking oil contaminated with PCBs from a heat transfer unit poisoned over 1600 people. The contaminating oil likely contained furans and dioxins, compounds generally more toxic than PCBs themselves. The ensuing illnesses became known as "Yusho" (rice oil disease).

The US federal government has taken the following steps:

• US EPA has set a maximum contaminant level of 0.0005 milligrams PCBs per liter of drinking water (0.0005 mg/L). The EPA requires that spills or accidental releases into the environment of 1 pound or more of PCBs be reported to the EPA.
• The Food and Drug Administration (FDA) requires that milk, eggs, other dairy products, poultry fat, fish, shellfish, and infant foods contain not more that 0.2–3 parts of PCBs per million parts (0.2–3 ppm).

Furan is a heterocyclic compound and potential carcinogen that has been identified in a number of foodstuffs that undergo thermal treatment such as bottled, canned and jarred food products. Some amino acids and sugars break down into furans when thermally treated. Other food components such as Vitamin C and polyunsaturated fatty acids may also produce furans as an unwanted byproduct of food processing. Ionizing radiation is also known to induce the formation of furan in solutions of simple sugars and ascorbic acid with where sugar content is high and pH is low, for example canned fruits and vegetables.