Dioxins

There are hundreds of chemical compounds that are included in the catch-all term dioxin. These compounds have had widespread uses in industry and agriculture. They are some of the most toxic chemicals known, do not break down readily in the environment, and thus can easily have unintended effects.

Some dioxins are polychlorinated biphenyls (PCBs), which are a broad family of chlorinated hydrocarbons. PCBs were used in a wide range of manufacturing from 1929 until they were banned in 1979. The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic. The toxicity of other dioxins and chemicals similar to PCBs that act like dioxin are measured in relation to TCDD.

[Page 131]Often dioxin is formed unintentionally when chlorine-based chemical compounds react with hydrocarbons. Many industrial processes that use chlorine use processes that create dioxins as a by-product. Waste incineration, chemical manufacturing, pesticide and herbicide production, pulp wood processing, and paper bleaching also produce dioxin.

Several localities and groups of people have been tragically affected by dioxin. It was the primary ingredient in Agent Orange used during the Vietnam War by the United States’ military. It had previously been used as an herbicide on crop land, but in Vietnam, it was used to defoliate vast areas of jungle. Two specific chemicals used were 2,4-D dichlorophenoxy (C8H6Cl2O3) and 2,45-T Trichlorophenoxy (C8H5Cl3O3) These chemicals are directly harmful to humans, and together they form dioxin (2,3,7,8-tetrachlorodibenzodioxin).

Dioxin is an infamous carcinogenic agent in humans that once caused numerous health problems at Love Canal, New York. The old chemical waste dump at Love Canal was used by people, with serious health consequences for many.

People were forced to evacuate from Times Beach, Missouri, because of the spraying of dirt roads that were later paved with waste oil containing high levels of dioxins. The city was disincorporated and demolished, forcing the removal of over 2,300 people.

Seveso, Italy, not far from Milan in northern Italy, suffered an industrial accident that exposed its people to dioxin. The town of 17,000 was forced to evacuate, and thousands more in surrounding towns were affected.

A common source for environmental pollution by dioxin is the unintentional production of dioxin in waste-burning incinerators. These can range from backyard barrel-burns to city or industrial waste incinerator burning. Other sources of dioxin pollution include paper mills that use chlorine bleaching. The chlorine reacts with organic compounds, which includes a huge number of carbon compounds. Other sources include the manufacture of polyvinyl chloride plastics and other chemicals including numerous chlorinated pesticides and herbicides.

Cancer and other diseases have been linked with dioxin. The World Health Organization's International Agency for Research on Cancer issued a report (February 14, 1997) stating that TCDD is now considered to be a class 1 carcinogen, which means that it has been scientifically identified as a known cancer-causing agent (carcinogen) in humans. In January 2001, the U.S. National Toxicology Program reclassified dioxin in the form 2,3,7,8-TCDD as a class 1 carcinogen. In 2002, dioxin was shown to be increasingly related to breast cancer.

Other health problems associated with dioxin include disruption of the reproductive system, interference with the immune system, and interference with the hormone system (endocrine system disrupters). Even low levels of dioxin can act to bind the compound to the hormone receptor of a cell. This in effect modifies how the cell functions and in some cases seems to adversely affect the genetic mechanism of cells. When dioxin is present in developing fetuses, it can promote miscarriages or birth defects; in infants, it can cause nervous disorders. Other implicated diseases are spina bifida (split spine), autism, liver disease, endometriosis, chronic fatigue syndrome, and blood disorders.

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