History

What are dioxins?

Dioxins are the most toxic chemicals known to science. The US Environmental Protection Agency and the World Health Organization(1) clearly describe dioxin as a serious public health threat.

Dioxins have been in the news recently with the poisoning of President Viktor Yushchenko of Ukraine in 2004(2) (who was ironically the leader of the Orange Revolution), the Naples Mozzarella Crisis of 2008(3), and the Irish pork crisis of 2008(4).

Personally, I was surprised to see how many areas of the United States(5) have been contaminated by dioxin—in states across the country: New Jersey, Texas, Oregon, Michigan, Maine, and even Alaska to name a few.

Dioxins are environmental pollutants(6). They have the dubious distinction of belonging to the "dirty dozen" - a group of dangerous chemicals known as persistent organic pollutants. Dioxins are of concern because of their highly toxic potential. Experiments have shown they affect a number of organs and systems.

According to a 1994 EPA report(7), not only does there appear to be no "safe" level of exposure to dioxin, but levels of dioxin and dioxin-like chemicals have been found in the general US population that are "at or near levels associated with adverse health effects."

This report led to controversy, as Big Industry(8) denounced the report and claimed the EPA was overstating risk. They argued there should be a "threshold" of exposure to dioxin, below which there was no risk. Scientists found no evidence for a threshold, as dioxins act like hormones do, disrupting many systems in the body.

In June 2000(9), the EPA released a revision of the 1994 report. Much to the chemical industry’s dismay, the EPA found even stronger links between exposure to dioxin and negative health effects.

The EPA found that the risk of getting cancer from dioxin exposure was ten times higher than reported in 1994. Let that sink in—over the course of 6 years, the danger to the average American became 10 times greater.

Once dioxins have entered the body, they endure for long periods because of their chemical stability and their ability to be absorbed by fat tissue, where they are then stored in the body.

The half-life of dioxins in the body is estimated to be seven to eleven years. In other words, it takes about 7 years for half of the dioxin in your body to be removed, and then another seven years for half of the amount remaining in your body to be removed and so on. This means your body will never be free of dioxin contamination.

In the environment, dioxins tend to accumulate in the food chain. The higher in the animal food chain one goes, the higher is the concentration of dioxins. A North American eating a typical North American diet will receive 90% of their dioxin exposure(10) from meat and dairy products. The name ‘dioxins’ is often used for the family of structurally and chemically related polychlorinated dibenzo para dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Certain dioxin-like polychlorinated biphenyls (PCBs) with similar toxic properties are also included under the term "dioxins". Some 419 types of dioxin-related compounds have been identified. About 30 of these are considered to have significant toxicity, with TCDD being the most toxic.

TCDD was a contaminant in the Agent Orange and Agent Purple used at Base Gagetown. TCDD is a by-product formed during the manufacture of 2,4,5-T when temperature controls are not maintained(11). Dioxins are formed unintentionally by industrial processes and incomplete combustion, such as: waste incineration, burning fuels (wood, coal or oil), chlorine bleaching of pulp and paper, and chlorinated pesticides manufacturing. Cigarette smoke and exhaust from cars also contain small amounts of dioxins.

Health effects of dioxins in humans

The US EPA reported that dioxins are a probable carcinogen, but noted that non-cancer effects may pose an even greater threat to human health. Dioxins build up primarily in fatty tissues over time, so even small exposures may eventually reach dangerous levels.

Exposure to high levels of dioxins may lead to the following effects in humans:

Recent studies have shown that exposure to dioxins changes the ratio of male to female births among a population. More females are born than males.

The developing fetus is most sensitive to dioxin exposure. The newborn, with rapidly developing organ systems, may also be more vulnerable to certain effects. Some individuals or groups of individuals may be exposed to higher levels of dioxins because of their diets (e.g., high consumers of fish in certain parts of the world) or their occupations (e.g., workers in the pulp and paper industry, in incineration plants and at hazardous waste sites, to name just a few).

Due to the omnipresence of dioxins, all people have background exposure and a certain level of dioxins in the body, leading to the so-called body burden. Current normal background exposure is not expected to affect human health on average. However, due to the high toxic potential of this class of compounds, efforts need to be undertaken to reduce current background exposure.

Health effects in animals

While it has been difficult to establish specific health effects in humans due to the lack of controlled dose experiments, studies in animals have shown that dioxin causes a wide variety of toxic effects.

Among the animals for which TCDD toxicity has been studied, there is strong evidence for the following effects: Birth defects (teratogenicity) in rats, mice, hamsters and guinea pigs, birds, and fish. Hepatotoxicity (liver toxicity) in rodents, chickens, and fish.

Endocrine disruption in rodents and fish

Immunosuppression in rodents and fish.

Cancer (including neoplasms in the mammalian lung, oral/nasal cavities, thyroid and adrenal glands, and liver, squamous cell carcinoma, and various animal hepatocarcinomas) in rodents and fish.

Footnotes

(1) http://www.who.int/mediacentre/factsheets/fs225/en/index.html

(2) http://news.bbc.co.uk/2/hi/health/4041321.stm

(3) http://www.nytimes.com/2008/03/26/world/europe/26italy.html

(4) http://news.bbc.co.uk/2/hi/uk_news/7770476.stm

(5) http://www.chej.org/BESAFE/pvc/documents/2009/letters/Quotes From Dioxin Impacted Communitiesx.pdf

(6) http://www.clu-in.org/contaminantfocus/default.focus/sec/Dioxins/cat/Toxicology/

(7) http://www.cqs.com/epa/exposure/

(8) http://www.dow.com/commitments/debates/dioxin/health/index.htm

(9) http://www.epa.gov/ncea/pdfs/dioxin/factsheets/dioxin_long2.pdf

(10) http://www.greenfacts.org/en/dioxins/index.htm#1

(11) http://encyclopedia.stateuniversity.com/pages/5935/dioxin.html