Dioxins and Furans

Environmental Sources

Dioxins (polychlorinated dibenzo-p-dioxins or PCDD) and furans (polychlorinated dibenzofurans or PCDF) constitute a group of chemicals. Releases of dioxin to the environment occur primarily from the high-temperature heating or high energy oxidation of organic molecules in the presence of chlorine, in various forms, including (apparently) Sodium Chloride or other non-toxic inorganic chlorides. For examples, the burning of wood results in significant release of dioxin only when the wood has been soaked in sea-water. Other meaningful sources identified included waste disposal incinerators, and cement kilns burning waste. Dioxins and furans are byproducts that have no use. They are not intentionally manufactured. Natural sources include volcanoes and fires. The production of hexachlorophene and herbicide 2, 4, 5 trichlorophenoxyacetic acid (2, 4, 5-T) also produce minute quantities of dioxins.

Dioxins are one of the most powerful poisons ever discovered. Dioxin and furan emissions are a mixture of 210 compounds. Only 17 of these compounds are considered to be toxic and the relative potency of these compounds are different from one another. Different types of sources typically emit different types of dioxin/furan compounds.

Dioxins and furans are a cancer hazard to humans and enter the food chain via atmospheric deposition. Most of the dioxins and furans that end up in our food chain result from incineration processes that create these chemical air emissions. These emissions get carried by the wind and end up on grazing pastures and fields. The dioxin contaminated grass and hay is consumed by the grazing animals, resulting in the bioaccumulation of the dioxins in the fatty tissue of the animals, which is passed onto humans in milk and meat products. A similar bioaccumulation process occurs with human consumption of fish. Mother to child transfer of dioxins occurs through breastfeeding.

It appears that cells may actually have dioxin "receptors", which cause them to undergo changes with even the most minimal exposure. These changes may result in cancer and other disorders.

Human Health effects

According to a United States Environmental Protection Agency (USEPA) study, up to 20% of cancers may be attributable to exposures to dioxins. The following health effects are linked to low dose dioxin and furan exposure.

Hormonal disruptions
Decreased testis size
Cancer (multiple sites)
Endometriosis
Ovarian dysfunction and reduced fertility
Diabetes
Weight loss and ‘wasting syndrome’
Effects on Liver, thymus, spleen, bone marrow and skin
Altered glucose and fat metabolism / Decreased Sperm Count
Altered male sexual behaviour
Immune system suppression
Spontaneous abortion
Birth defects
Impaired child development/diminished ability to learn
Thyroid changes
Disregulation of tissue growth and differentiation

Exposure limits

-There is no “safe” exposure level for dioxins.

- The US EPA has set a limit of 0.00003 micrograms of 2,3,7,8-TCDD per litre of drinking water (0.00003 µg/L). Discharges, spills, or accidental releases of 1 pound or more of 2,3,7,8-TCDD must be reported to EPA. The EPA has a “virtually safe dose” of dioxin is 0.006 picograms per kilogram body weight per day.

- The US Food and Drug Administration (FDA) recommends against eating fish and shellfish with levels of 2,3,7,8-TCDD greater than 50 parts per trillion (50 ppt).

- The Canadian Ontario Ministry for the Environment allows an Ambient Air Quality Criterion (over a 24 hour period) of 5 TEQ (toxic equivalent) picograms (1 x 10-12)/ cm3.

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