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Dioxins and furans are highly toxic chemicals that accumulate in animal fatty tissue and can be found in the food supply. They are produced through industrial processes such as waste incineration and paper bleaching. PCBs, which contain these compounds, were banned in 1977 but still remain in the environment. Exposure to these chemicals has been linked to adverse health effects in humans and animals. The primary method of exposure is through the food supply, particularly meat, dairy, and egg products. The combustion of chlorinated products is the largest source of air pollution for dioxins and furans.
Dioxins and furans belong to a chemical family with similar structures. These chemicals include polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). Although both dioxins and furans are unintended by-products of pesticide production and paper bleaching, they are a family of highly toxic chemicals. Dioxins are considered the most toxic chemicals ever produced by man and furans are about one tenth as dangerous. Environmentally, they are persistent chemicals that accumulate in the fatty tissue of animals, and vectors of human exposure include the food supply and air and water contamination.
These contaminants are typically produced through the processes used by solid waste incinerators, such as copper smelters and coal-fired power plants. Other common sources of chemicals include medical waste incineration, cement kilns, and wood burning, among others. Two industrial processes responsible for much of the production of dioxins and furans include the use of chlorine-based chemicals to bleach paper and pulp and the burning of materials that contain polyvinyl chloride (PVC) plastics.
About 95% of the air pollution level for dioxins and furans comes from the combustion of chlorinated products. The largest source of these is municipal waste incineration. Past large-scale use of PCBs and the burning of materials containing them in waste can increase the levels of dioxins and furans present at temperatures between 492° and 842° Fahrenheit (250-450° Celsius).
Although the use of PCB chemicals that contained these compounds was stopped in 1977, they still remain in the environment. Concentrations worldwide are high enough as of 2011 that 10% of the normal background level of exposure to chemicals has been shown to cause adverse health effects in humans and animals. Of particular concern is their occurrence in the food supply, which is the primary method of exposure. They are found in most meat, dairy and egg products. Tests have shown that consuming one beef burger from a US fast food chain contains 250 times what is considered an acceptable daily exposure to chemicals.
Areas where dioxins and furans have had widespread detrimental health effects include Vietnam due to their presence in the Agent Orange defoliant used in the Vietnam War and environmental cleanup sites such as Times Beach, Missouri and Love Canal, New York, in WE. Rice oil used in Taiwan and Japan as a high-temperature cooking method of fish also raises the levels of furan where PCBs are present. Fish are a major route of exposure for the chemicals, and a 2001 study that ranked the levels of dioxins and furans found in breast milk listed Vietnam with the highest concentrations and Japan as second.
Exposure to dioxins and furans in the environment is a worldwide concern. A study of their environmental presence was conducted by drilling the bottoms of lakes in the United States and Switzerland. The deeper the core, the further back in time the sediment can be traced, and dioxins were found to be almost undetectable in the environment as of the 1940s. The conclusion was that the combustion of chlorinated aromatic materials as a result of industrial processes has since been the major source of these contaminants.
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