Dioxins Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Dioxins are a class of 75 chlorinated aromatic hydrocarbons that vary widely in their toxicity to humans. Dioxin toxicity is measured by Toxic Equivalent Factor (TEF) for which the standard of 1.0 is TCDD, or tetrachlorodibenzo-p-dioxin, one of the most toxic substances known. Dioxins are chemically and toxicologically related to chemicals known as furans, and some of the polychlorinated biphenols, or PCBs. Dioxins have no commercial application and can be produced as byproducts of manufacturing processes involving chlorine or fire in the presence of chlorine and complex carbon molecules.

Dioxins are more soluble in fat than water, meaning they bind to organic matter and bioaccumulate. Human exposure to dioxin is generally through consuming animal-based foods like meat, dairy, and eggs, making exposures widespread. Dioxins are very persistent in the environment and do not migrate easily through groundwater or vaporize into the air. Much is unknown about the causes and effects of dioxin toxicity, but it appears it influences endocrine function affecting fetal development, the reproductive system and the liver, and is associated with some cancers. Dioxin is believed to act through binding to a receptor protein that enters the cell nucleus and affects gene expression. In acute doses, dioxin can cause a skin condition known as chloracne, and its hormonal effects can be evident in extremely tiny doses of parts per trillion.

The sources of dioxin are almost entirely anthropogenic. The EPA estimate conducted in 2003 found that the vast majority of releases in the United States were into the air, and about half of those from medical and municipal waste incinerators. Most of the remainder came from backyard burning of trash, cement kilns, and fuel combustion.

Science and Politics Of Dioxin

The science and politics of dioxin have been marked by a series of controversies related to where dioxin comes from, what it does to people, and what constitutes an acceptable level of risk, punctuated by periodic environmental justice flashpoints centering on dioxin exposure. Industrial accidents involving dioxin provided contested evidence of dioxin’s dangers. The involved corporations found no link between dioxin exposure and illness in the studies they paid for and conducted, while independent studies found significant increases in cancer in exposed people.

A series of broad-scale dioxin exposures that occurred in the 1960s and 1970s made dioxin a major environmental justice issue. From 1962-71, the U.S. Air Force sprayed large areas of South Vietnam with Agent Orange, a mix of herbicides including 2,4,5-T and 2,4-D, organochlorine chemicals that contained substantial amounts of dioxin byproducts. American veterans’ health problems from Agent Orange led to a series of studies that found many veterans’ health conditions were due to their exposure to dioxin.

Love Canal was a site where tens of thousands of tons of chemical waste containing dioxin was dumped and subsequently leached into groundwater, mobilizing the dioxin that readily diffuses through oily solvents. The health problems faced by Love Canal residents made public in the late 1970s accelerated attention from the environmental justice movement, government, and corporations on dioxin. Other dioxin hotspots were the Alsea river valley in Oregon where 2,4,5-T was sprayed, causing widespread birth defects; and Times Beach, Missouri, where dioxin-polluted oil was sprayed to keep down dust on roads and subsequently contaminated the town.

Around this time Dow Chemical Company, a manufacturer of many products linked to dioxin, came out with a paper entitled “Trace Chemistries of Fire” that contended dioxin came not from human activity, but was produced naturally from forest fires. This theory was quickly refuted, but the role of natural combustion in global dioxin production continues to be promoted by spokespeople for industries tied to dioxin pollution.

The EPA made its first assessment of dioxin’s public health implications in 1985, and has issued three reassessments since: in 1988, 1994, and 2003. The magnitude of exposure and its consequences remains much disputed. Although EPA reported in 2003 that dioxin emissions fell about 75 percent since 1987 (mostly due to reductions in incinerator emissions) and dioxin concentrations in food have declined considerably since 1970, the EPA admits that the cancer risk from dioxin to the general U.S. public may exceed 1 in 1,000. This level is three magnitudes greater than the generally accepted one in a million acceptable risk. The average body burden of dioxin in the U.S. public approaches the minimum level at which harm may result.

Bibliography:

T. Colborn et , Our Stolen Future (Plume, 1997);
Gibbs and Citizens Clearinghouse for Hazardous Waste, Dying From Dioxin: A Citizen’s Guide to Reclaiming our Health and Rebuilding Democracy. (South End Press, 1995);
Steingraber, Living Downstream (Vintage, 1998).