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.
Sources & Links:
www.eurochlor.org/PDF/29%20Chlorine%20Online%20-%20Chlorine%20-%20Issues%20-%20Dioxins.pdf
www.epa.gov/epaoswer/hazwaste/combust/faqs.htm#esp
www.rec.org/Poland/WPA/pyro2.htm
http://web.bham.ac.uk/CM/Tarpey/phil.htm
http://www.ijc.org/boards/iaqab/incin.htm#opt
www.greenpeace.org/~usa/reports/toxics/PVC/cradle/dcgtoc.html
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