PCBs, Dioxins, Furans and Mercury

They Travel Together


dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Industry representatives argue that some PCB health studies in humans are inconclusive because the victims were exposed to mixtures of PCBs which included traces of dioxins and furans. Sometimes, they point to toxic mercury contamination in our Fox River and Green Bay fish as more important than the PCBs.

But the reality is that local fish eaters are exposed to ALL these chemicals at the same time (plus hundreds of other chemicals), because they’re all present in the fish, sediment, and water of the River and Bay.  We face a much larger total health risk as a result.

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Dioxins and Furans are Highly Toxic

Dioxin is considered one of the most toxic man-made chemicals ever made, and furans are about a tenth as toxic. In addition, twelve of the 209 kinds of PCBs are very similar to dioxin in structure and toxicity (about one hundredth as toxic). All three compounds (dioxins, furans and PCBs) are often referred to collectively as “dioxin.” They are scored for their dioxin-like potency, and described in terms of their “Toxic Equivalency Factor” (TEF) relative to dioxin. (The other non-dioxin-like PCBs have different toxic properties.)

Dioxin is the well-known toxic chemical which contaminanted Agent Orange — a defoliant used to clear forests in the Vietnam war — and caused the evacuation of the town of Times Beach, Missouri, in 1983 and of the Love Canal site in Niagara
Falls, New York, in 1978.

Over the last 30 years, since the end of the
Vietnam War, serious birth defects have been
common in Vietnam.  Scientists believe the dioxin
in Agent Orange is causing the birth defects.

Dioxin has been the subject of an intensive health reassessment by EPA for more than 10 years. Industries originally pushed for the reassessment, but didn’t get the results they expected. Now they’ve spent years lobbying against the release of the study. Currently, the Bush Administration is delaying the release of the final results, but it is widely known that the scientists have determined that dioxins and dioxin-like compounds (such as PCBs) are “known carcinogens.” They conclude that the average American may face a 1 in 1,000 risk of cancer due to these compounds, perhaps a risk as high as 1 in 100, because contamination has become so widespread in our general food supply (particularly in meat, dairy, poultry, fish, eggs and other fatty animal products.)

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

PCBs Were Made With Dioxin and Furan Contaminants

By 1956, or earlier, Monsanto knew that their PCB products could be contaminated with dioxins (TCDD) and dibenzofurans (furans) from the time they were shipped from the factory—a piece of information the company sat on until the late 1960s, when independent researchers discovered this hazard. When PCBs were made, the dioxins and furans were created as byproducts in the mixtures. According to the record of one lawsuit, new PCB oil could be contaminated with dibenzofurans at concentrations of up to 10 parts per million. As the oil ages, according to documents from Monsanto’s files, the concentration becomes considerably higher. Additional references listed below confirm this contamination.

This means that the 7 corporations who dumped PCBs in the Fox River were also likely to dump furans and dioxins at the same time. Both furans and dioxins have been found at significant levels in Fox River sediment and fish.

Unfortunately, many PCB health studies underestimate total health risks in the real world because researchers have used “pure” PCBs without the usual dioxin or furan contaminants. (Monsanto did this deliberately in the 1970s — see the History section.)

The structures and components of dioxins, furans and PCBs are very similar.

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Heated or Burned PCBs are More Dangerous

The boiling point of PCBs is about 325-366 degrees Centigrade, so PCBs can tolerate fairly high temperatures without exploding or burning. Unfortunately, furans are created from PCBs at 250-450 degrees C, which means that simply heating PCBs can convert them to create additional furans in the mixture. This heat-effect explains how PCBs came to be contaminated in the manufacturing process.

It’s possible that high-temperature pan frying or grilling of fish or other PCB contaminated foods could convert some of the PCBs to more-toxic dioxins and furans. (The PCBs would also volatilize into the kitchen air at high rates.) The EPA reports that some of the toxic effects of rice-oil PCB poisoning incidents in Taiwan and Japan involved heat conversion of PCBs to furans. (EPA, 1997)

PCBs will burn at higher temperatures, but some of the PCBs will be converted to furans and dioxins, especially in poorly controlled, inconsistent fires. When PCBs are burned at very high temperatures, as in hazardous waste incinerators designed for this purpose, the PCBs may be completely broken down, but as the gases leave the smoke stack they cool and recombine to form new PCBs, furans and dioxins. Municipal waste incineration is the major global source of dioxins.

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Oxidation and Additives May Increase Toxicity

Over time, aging PCB mixtures oxidized, especially if exposed to heat or other catalyzing chemicals. PCB oils used in transformers often included chemicals designed to inhibit oxidation of the oils (see Velcon website). Nevertheless, PCBs still degraded. According to the Fluidex/SD Meyers webpage, “As oil ages in a transformer, it oxidizes and begins to break down. Some of the by-products of this degradation are acids, aldehydes and peroxides.” This forced the replacement of old PCB oil with fresh oil. It’s likely that Appleton Paper and NCR Corporation also had to account for the aging of their PCB mixtures and they may have included additives to inhibit oxidation. (Some of the research studies on this site indicate that oxidized PCBs also have distinct toxic properties.)

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Dioxin-like PCBs Are More Likely to Accumulate in Fish

The higher-chlorinated and dioxin-like PCBs (plus dioxins and furans) are much more likely to be picked up and retained in fish and in the human body, compared to the lower-chlorinated, light-weight PCBs. These dioxin-like compounds are also slower to breakdown. (The lightweight PCBs are more likely to degrade, blow off in the air or stay dissolved in the water and flow north to Upper Green Bay and Lake Michigan.) This means that even in cases where “total PCB” measurements in fish are declining, the more toxic dioxin-like forms could be increasing locally in intensity and health effects in the Fox River and Lower Green Bay. Dioxin-like compounds are strongly linked to cancer.

Many animal studies of PCB toxicity used virgin commercial mixtures of PCBs called by their tradename: “Aroclor.” These mixtures were not consistent as to relative amounts of the 209 kinds of individual PCB types. Also, they were usually purified of dioxin or furan contaminants (Monsanto did this deliberately in the 1970s — see the History section.) This means the researchers were testing a PCB mix very different from the highly toxic mixture that actually accumulates in fish. This could lead to serious underestimates of the true human health effects of PCBs, plus dioxins and furans.

political cartoonshttp://www.foxriverwatch.com/cartoons/foxlogoinfo1.jpgpolitical cartoons

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Mercury Levels are High in Fox River Sediments and Fish

If it weren’t for the overwhelming amounts of PCBs in the Fox River, the serious mercury contamination might get more attention. In past years, the pulp and paper industry used mercury compounds as “slimacides” to prevent bacterial or fungal growth on wood stocks and paper pulp. Chlor-alkali production plants were also used in the Fox River Valley to break salt into chlorine and NaOH (caustic soda), which are both used in huge quantities by the paper industry. Mercury was the catalyst in this chemical splitting of salt. As a result, the Fox River became contaminated as the mercury found its way into wastewater discharges to the river. Other important ongoing sources of PCBs include coal-fired power plants and waste incinerators (mercury escapes the pollution controls as a gas).

Mercury is a nerve poison and especially dangerous for unborn and developing babies. As mentioned in the Baby Studies, evidence is building that mercury and PCBs together are much more toxic than either one individually or simply added together. Some of the learning disabilities seen in Great Lakes children studies may be due to the multiplied health effect (synergism) of these chemicals together.

Wisconsin and Michigan anglers who use inland lakes for fishing are being exposed to mercury, and if they also eat fish from the Fox River, Green Bay and Lake Michigan, they’re getting dosed with both toxic chemicals. Fish sold in stores and restaurants are often contaminated with mercury, especially tuna, swordfish and salmon. Mercury is found in the muscle tissue and will not be reduced in a fish fillet by trimming off the fat.

Unfortunately, the U.S. Food and Drug Administration is balking at tightening the human health standards based on more up-to-date science, due to the harm this would cause to the commercial fishing industry and the food industry in general. Numerous agencies are pushing consumers to eat MORE fish with the claim of health benefits, which seems contradictory given widespread fish contamination problems.

The Wisconsin DNR and Wisconsin Division of Health issue a fish-eating advisory which gives information on fish contamination in various lakes and rivers of the state. Visit their online site for details.

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF

Links to More Information

Wisconsin Fish Consumption Advisories
The Dioxin Homepage
The Draft EPA Dioxin Reassessment
EPA’s Mercury Page
Wisconsin Mercury Sourcebook
Mercury Action Alert — Wisconsin’s Environmental Decade
Mercury in Wisconsin Fish
Mercury Free – What’s In It For Me? (Wisconsin DNR)
Mercury Page for the U.S. Geological Survey

dioxins, furans, Agent Orange, mercury, TCDD, TCDF, TEF


EPA, “Integrated Risk Information System” – Polychlorinated biphenyls (PCBs) CASRN 1336-36-3, (06/01/1997) Quote: “Serious adverse health effects, including liver cancer and skin disorders, have been observed in humans who consumed rice oil contaminated with PCBs in the “Yusho” incident in Japan or the “Yu-Cheng” incident in Taiwan. These effects have been attributed, at least in part, to heating of the PCBs and rice oil, causing formation of chlorinated dibenzofurans, which have the same mode of action as some PCB congeners (ATSDR, 1993; Safe, 1994) Quote: “It is crucial to recognize that commercial PCBs tested in laboratory animals were not subject to prior selective retention of persistent congeners through the food chain (that is, the rats were fed Aroclor mixtures, not environmental mixtures that had been bioaccumulated). Bioaccumulated PCBs appear to be more toxic than commercial PCBs (Aulerich et al., 1986; Hornshaw et al., 1983) and appear to be more persistent in the body (Hovinga et al., 1992). For exposure through the food chain, risks can be higher than those estimated in this assessment.” Webpage: http://www.epa.gov/IRIS/subst/0294.htm

EPA. “PCBs: Cancer dose-response assessment and application to environmental mixtures.”Quote: “Table 1-1. Typical composition (%) of some commercial PCB mixtures – [at the bottom of the table:] “Impurities include chlorinated dibenzofurans and naphthalenes; see WHO (1993) for sample concentrations.” Webpage:

Erickson, M.D., “Analytical Chemistry of PCBs.” Butterworth Publishers, Boston, 1991. Dibenzo-furans were found as contaminants in commercial PCB mixtures at part-per-million levels, which varied batch-to-batch. (Per public forum communication from Mark Harkness, GE Engineer)

European Science Foundation. “Workshop on Dioxin Food Contamination, Bayreuth.” September 29 – 1 October 2000 Quote: “In January 1999 a storage tank for animal fat in Belgium was badly contaminated with dioxins, furans and PCB. The contamination seems to have been caused by the discharge of about 25 liters of PCB transformer oil into a waste collection unit for animal fats recycled into animals feed.” Webpage:http://www.esf.org/update/news/00/dioxin.htm

Fluidex, SD Myers webpage: “As oil ages in a transformer, it oxidizes and begins to break down. Some of the by-products of this degradation are acids, aldehydes and peroxides.” Webpage:http://www.sdmyers.com/fluidex/

Francis, Eric. “Conspiracy of Silence: The story of how three corporate giants— Monsanto , GE and Westinghouse—covered their toxic trail.” From Sierra magazine, cover story, Sept./Oct. 1994. http://www.planetwaves.net/silence.html

Health Canada [the Canadian version of the EPA], “It’s Your Health – Dioxins & Furans.” Quote:“Polychlorinated biphenyls (PCBs) used to be an important source of furans, which are contaminants in commercial PCB mixtures.” Webpage: http://www.hc-sc.gc.ca/ehp/ehd/catalogue/general/iyh/dioxins.htm

IARC Anonymous. Polychlorinated biphenyls. International Agency for Research on Cancer (IARC) Monographs on the evaluation of the carcinogenic risk of chemicals to humans PG:43-103 YR:1978 IP: VI:18 Quote: “Almost without exception, polychlorinated biphenyls contain various levels of polychlorinated dibenzofurans as contaminants.”

Paddock, Todd. “Dioxins and Furans: Where They Come From,” Academy of Natural Sciences, Philadelphia, July, 1989. Quote: “Polychlorinated biphenyls (PCBs) have been widely used as cooling fluids in electrical equipment and some industrial cooling systems. Such fluids are often a mixture of PCBs and other chemicals. PCBs can contain low levels of furans, and the other chemicals can contain low levels of both dioxins and furans.” Webpage:http://www.acnatsci.org/erd/ea/diox2.html

United Nations. “Persistent Organic Pollutants – Working Group Reports, Working Group Industrial Chemicals and Contaminants” Quote: “Poland: Poland produced PCBs and organochlorine pesticides. PCDDs/Fs were found in transformer oil.” [PCDDs/Fs = dioxins & furans] Webpage: http://www.chem.unep.ch/pops/POPs_Inc/proceedings/slovenia/KWG.html

Velcon, describing their SuperDri Cartridges for removing water from transformer oils: “Will not remove oxidation inhibitors.” Webpage: http://www.velcon.com/superdri.htm





Renard Isle – Green Bay, WI

Renard Isle(also known as Kidney Island) was created in 1977 by the United States Army Corps of Engineers. The 55 acre toxic island was created as a disposal site for 2.7 million cubic yards of sediment dredged from the Fox River navigational channel. It hasn’t been used since the early 1990s however plans are underway to build a bridge to it to truck in 450,000 more cubic yards before it is capped off by 2013.

Today there are 24 paper mills along the Fox River that produce more than five million tons of paper a year and employ over fifty thousand people in the community. In the 1950s the paper industry began to produce carbonless copy paper that used the chemical Polychlorinated biphenyls (PCBs) in the ink on the back of the paper. These mills began dumping PCB waste into the Fox River and continued to do so until the EPA halted the use of PCBs in 1977. PCBs have been linked to human heart disease, liver damage, diabetes and auto-immune diseases in humans. The health concerns has caused commercial fishing to be outlawed in Green Bay in 1956. It is generally understood you don’t eat fish out of the Bay.

The City of Green Bay has shown interest in obtaining the land from the government after it is capped to keep the PCBs in. However, some experts say this may be a bad idea in the event it is not capped properly increasing toxic exposure from the PCBs in the future. There currently is a 2013 deadline to cap the island.

The cleanup costs are expected to reach as high as $1.5 billion dollars.



What is dioxin?

Dioxins and furans are some of the most toxic chemicals known to science. A draft report released for public comment in September 1994 by the US Environmental Protection Agency clearly describes dioxin as a serious public health threat. The public health impact of dioxin may rival the impact that DDT had on public health in the 1960’s. According to the EPA report, 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.”

Dioxin is a general term that describes a group of hundreds of chemicals that are highly persistent in the environment. The most toxic compound is 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD. The toxicity of other dioxins and chemicals like PCBs that act like dioxin are measured in relation to TCDD. Dioxin is formed as an unintentional by-product of many industrial processes involving chlorine such as waste incineration, chemical and pesticide manufacturing and pulp and paper bleaching. Dioxin was the primary toxic component of Agent Orange, was found at Love Canal in Niagara Falls, NY and was the basis for evacuations at Times Beach, MO and Seveso, Italy.

Dioxin is formed by burning chlorine-based chemical compounds with hydrocarbons. The major source of dioxin in the environment comes from waste-burning incinerators of various sorts and also from backyard burn-barrels. Dioxin pollution is also affiliated with paper mills which use chlorine bleaching in their process and with the production of Polyvinyl Chloride (PVC) plastics and with the production of certain chlorinated chemicals (like many pesticides).

Does dioxin cause cancer?

Yes. The EPA report confirmed that dioxin is a cancer hazard to people. In 1997, the International Agency for Research on Cancer (IARC) — part of the World Health Organization — published their research into dioxins and furans and announced on February 14, 1997, that the most potent dioxin, 2,3,7,8-TCDD, is a now considered a Group 1 carcinogen, meaning that it’s a known human carcinogen.

Also, in January 2001, the U.S. National Toxicology Program upgraded 2,3,7,8-TCDD from “Reasonably Anticipated to be a Human Carcinogen” to “Known to be a Human Carcinogen.” See their reports on dioxins and furans from their 11th Report on Carcinogens (find related documents under 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and Furan). Finally, a 2003 re-analysis of the cancer risk from dioxin reaffirmed that there is no known “safe dose” or “threshold” below which dioxin will not cause cancer.

A July 2002 study shows dioxin to be related to increased incidence of breast cancer.

What other health problems are linked to dioxin exposure?

In addition to cancer, exposure to dioxin can also cause severe reproductive and developmental problems (at levels 100 times lower than those associated with its cancer causing effects). Dioxin is well-known for its ability to damage the immune system and interfere with hormonal systems.

Dioxin exposure has been linked to birth defects, inability to maintain pregnancy, decreased fertility, reduced sperm counts, endometriosis, diabetes, learning disabilities, immune system suppression, lung problems, skin disorders, lowered testosterone levels and much more. For an detailed list of health problems related to dioxin, read the People’s Report on Dioxin.

How are we exposed to dioxin?

The major sources of dioxin are in our diet. Since dioxin is fat-soluble, it bioaccumulates, climbing up the food chain. A North American eating a typical North American diet will receive 93% of their dioxin exposure from meat and dairy products (23% is from milk and dairy alone; the other large sources of exposure are beef, fish, pork, poultry and eggs). In fish, these toxins bioaccumulate up the food chain so that dioxin levels in fish are 100,000 times that of the surrounding environment. The best way to avoid dioxin exposure is to reduce or eliminate your consumption of meat and dairy products by adopting a vegan diet.According to a May 2001 study of dioxin in foods, “The category with the lowest [dioxin] level was a simulated vegan diet, with 0.09 ppt…. Blood dioxin levels in pure vegans have also been found to be very low in comparison with the general population, indicating a lower contribution of these foods to human dioxin body burden.”

In EPA’s dioxin report, they refer to dioxin as hydrophobic (water-fearing) and lipophilic (fat-loving). This means that dioxin, when it settles on water bodies, will rapidly accumulate in fish rather than remain in the water. The same goes for other wildlife. Dioxin works its way to the top of the food chain.

Men have no ways to get rid of dioxin other than letting it break down according to its chemical half-lives. Women, on the other hand, have two ways which it can exit their bodies:

  • It crosses the placenta… into the growing infant;
  • It is present in the fatty breast milk, which is also a route of exposure which doses the infant, making breast-feeding for non-vegan/vegetarian mothers quite hazardous.

If you’re eating the typical North American diet, this is where you are getting your dioxin from:

Dioxin Exposure Chart
Chart from EPA Dioxin Reassessment Summary 4/94 – Vol. 1, p. 37
(Figure II-5. Background TEQ exposures for North America by pathway)

[A TEQ is a dioxin Toxic EQuivalent, calculated by looking at all toxic dioxins and furans and measuring them in terms of the most toxic form of dioxin, 2,3,7,8-TCDD. This means that some dioxins/furans might only count as half a TEQ if it’s half as toxic as 2,3,7,8-TCDD.]

Levels of Dioxin in U.S. Food Supply (1995):

Dioxin Levels in Food

[Chart from May 2001 study by Arnold Schecter et. al., Journal of Toxicology and Environmental Health, Part A, 63:1–18]

Note: freshwater fish were farm-raised on a diet of meat, which is why they show the highest dioxin levels in this study.

For more information on dioxin in the food supply…

EPA’s Dioxin Reassessment Report and Related Government Documents

Where Dioxin Comes From:

Health Effects Reports:

Read about the convoluted nearly 25+ year history of EPA’s dioxin reassessment to learn why it is still not out in final form. For more details on this, read the Behind Closed Doors report about the chemical industry’s efforts to block final release of EPA’s dioxin report.

U.S. General Accounting Office (GAO) Reports:

All You Ever Wanted To Know About Dioxin

Or Perhaps You Really Do Not Want To Know?

For many more links on Dioxin click http://www.ejnet.org/dioxin/ there are over 150 other links about Dioxin
The most deadly dioxin is 2,3,7,8-tetrachloro dibenzo-p- dioxin or TCDD.
TCDD is more commonly recognized as the toxic contaminant found in Agent Orange and atLove Canal, NY and Times Beach, Missouri and Canadian Forces Base Gagetown.
There are 75 chlorinated dioxins, 135 chlorinated furans and 209 polychlorinated biphenyls or PCBs. Of the 419 chemicals from all three families, 30 have dioxin-like toxicity. We’re usually exposed to a mixture of toxic and non-toxic members of the larger family at the same time.
When we say “dioxin” we are referring to the 30 dioxin-like chemicals of this family.
Q: Why is dioxin produced?
A: Dioxin is not manufactured intentionally. They form as an unintended contaminant or by- product during combustion or during the manufacture of certain chlorinated chemicals.
Q: How do they get into the environment?
A: Dioxins and furans can be produced when almost anything is burned under the right conditions. Two major sources are municipal waste and hospital incinerators, though emissions from these sources have been reduced in recent years because so many of these incinerators have shut down in recent years in many cases due to opposition from local grassroots community based organizations. Bleaching wood pulp with chlorine to make paper white has been another major source. Dioxin is found in the waste water released from these plants, although the amounts have declined because many plants have converted to processes that use less chlorine.
PCBs were used as insulators in electrical equipment, but their production was banned in 1977. Today, they remain in use mostly in electrical transformers and capacitors, especially in large office or apartment buildings.
PCBs are commonly found in river sediment nears plants where PCBs were generated or used.
Q: Does dioxin break down in the environment?
A: Dioxin is a highly persistent chemical that only slowly degrades in the environment. Dioxin present in surface soil may take from 9 to 15 years to degrade to half its concentration. In subsurface soil, dioxin will remain largely unchanged with time. Dioxin in water settles in sediment and can re-enter the water when the sediment are disturbed.
Q: How do dioxin emissions from incinerators reach people?
A: Dioxin goes into the air and people breathe in the particles. But a bigger problem is that the particles settle on grazing land where cows eat the grass and the dioxin gets concentrated in the fat in their meat and milk.
It also gets concentrated in cattle and hogs that are fed dioxin- tainted grain.
Dioxin particles can also fall directly into rivers, streams, and other bodies of water or reach these waterways in surface water runoff. Dioxin settles on the bottom where fish and shellfish ingest small particles of sediment. Dioxin then builds up in their fat or organs. In Maine, pregnant women are advised not to eat the green “guts” in lobsters because it’s high in dioxin. People call it the “tomalley,” but it’s actually a combined liver and pancreas – a hepatopancreas.
Q: Do dioxins concentrate as they move up the food chain?
A: Yes. More than 90 percent of our exposure comes from food, mostly fish, meat, poultry, and non-skim dairy products. Fattier fish have more dioxin than leaner fish. Shellfish like lobsters are low in fat, but the dioxin may be in their hepatopancreas or organs, not the meat.
Q: Does dioxin accumulate in our bodies?
A: Yes. Dioxin slowly accumulates in the body. The average levels of dioxin in the U.S. population is about 25 parts per trillion (ppt) according to the US Environmental Protection Agency (EPA). Approximately 10% of the population may have tissue levels has much as 3 times higher than this level.
Q: What does it mean to have dioxin in our bodies?
A: The USEPA has found that the body burden level of dioxin in animal studies can be relate to adverse health effects observed in both animals and people.
They have also found that the average level of dioxin found in the general US population is very close to these levels. EPA interprets this to mean that there is little or no “margin of exposure” left for most people. We see this as meaning that we are nearly “full” and that any additional exposure of dioxin can result in adverse health effects. Some people already have body burden levels that are above the average and they are likely already suffering adverse health effects.
Q: Are some people more at risk from exposure to dioxin?
A: Yes. Nursing infants, some workers, people who eat fish as a main staple of their diet, such as indigenous people and fishermen, and people who live near dioxin release sources are at greater risk of developing adverse health effects from dioxin because they are exposed to higher concentrations.
Q: Can you get rid of dioxin?
A: Yes, but not easily. There’s a general process within the body of accumulation and removal of toxic substances. Dioxin is accumulated in fat which is hard to get rid of. If you lose weight, you lose some dioxin with the fat. If you’re breastfeeding, you get rid of it through the breast milk. Infants get their greatest dose of dioxin during breastfeeding because it’s concentrated in breast milk and because the infant is so small that the dose per pound of body weight is quite high. The benefits of breastfeeding still outweigh the risks of dioxin, though we’d rather not have to make such a choice.
Q: How long does it take to get rid of dioxin?
A: Dioxin’s “half-life” in the human body is about seven years. In other words, it takes about seven years for half of the dioxin in your body to be removed and then another seven years for the half of that amount and so on. This means your body will never be free of dioxin contamination.
Q: What harm does dioxin cause?
A: Exposure to dioxin can lead to a wide arrays of adverse health effects including cancer, birth defects, diabetes, learning and developmental delays, endometriosis, and immune system abnormalities.
Q: How can dioxin affect so many parts of the body?
A: Dioxin binds very strongly to intracellular receptors in the nuclei of animal and human cells throughout the body. So dioxin can easily get into the nucleus, where the cell’s DNA is located, and wreak havoc. If it damages the DNA, that could cause cancer or birth defects. It could also alter the DNA’s instructions to make normal enzymes, hormones, and other proteins, which could lead to any of a number of diseases.
Q: Can dioxin cause cancer?
A: Yes. Dioxin is a known carcinogen. TCDD is the most potent animal carcinogen ever tested. It causes tumors in both genders of every species and every strain of animal that’s been tested. And the animals get different types of tumors, so it doesn’t just initiate tumors, it also promotes the growth of tumors caused by other chemical initiators.
Q: Does dioxin also cause cancer in people?
A: Yes. Everyone, except perhaps some industry groups, accepts that dioxin is a human carcinogen.
IARC, the International Agency for Research on Cancer, which is part of the World Health Organization (WHO), reclassified it as a human carcinogen in 1997. In January 2001, the Department of Human Health and Services’ National Toxicology Program classified dioxin as a known human carcinogen. The September 2000 draft of the USEPA’s Health Assessment document on dioxin also classifies dioxin as a known human carcinogen.
Q: How powerful a carcinogen is dioxin?
A: It is the most potent substance ever tested by the USEPA or by any private or government research center. Dioxin causes cancer in multiple species in multiple organs in both sexes. Cancer in animals has resulted from exposures as low as 200 ppt.
Q: What’s the chance that you will get cancer as a result of exposure
to dioxin?
A: The USEPA released a draft report last fall that projected an excess cancer risk of one in 100 for the most sensitive people who consume a diet high in animal fats. In other words, the risk of getting cancer from dioxin – over and above the risk of cancer from other sources – is one in 100 for some people. This is a worst-case scenario. It’s for the most sensitive people among the five percent of the population who consume the most dioxin. Scientists refer to this as the “upper bound estimate.” This is a shocking estimate.
EPA’s upper bound risk for the most sensitive people to average exposure is one in 1,000 which is also a serious risk level. A general “acceptable” risk level is one-in-one-million.
Some people may be exposed to little if any dioxin.
Q: Are the EPA’s risk estimates reliable?
A: They’re the most reliable ones we have. Several scientific peer review groups, including the agency’s Scientific Advisory Board, which includes consultants outside of the agency have approved the agency’s report including the methods EPA used to make their risk estimates.
Q: What kind of cancer does dioxin cause in people?
A: Most of the studies of exposed populations indicate that dioxin causes an increased risk of all cancers. Some studies suggest that it promotes lung cancer and soft-tissue sarcomas, which are cancers of the fat and muscle. Most studies don’t focus on any one type of cancer because there are so few individual cancers in small studies of exposed populations.
Q: What other health problems does dioxin cause?
A: Dioxin exposure is linked to skin rashes, liver disorders, reproductive problems, birth defects, learning and developmental delays, endometriosis, immune system abnormalities, and diabetes.
Q: Do dioxins impair learning behavior?
A: PCBs appear to lower IQ or cause developmental delays in the children of women who ate large quantities of PCB-tainted fish during pregnancy. The studies that monitor these children are still on-going, so we don’t know for how long the adverse effects last. Up until age seven, researchers are still finding measurable developmental delays. Over time, those delays may become imperceptible, but we don’t know about IQ.
Q: How does dioxin affect reproduction?
A: Dioxins seem to impair the development of the human reproductive system. There have been case reports of hypospadias- -a birth defect in which the urethra opens on the underside of the penis–in populations exposed to dioxin.
Dioxin has been shown to cause either endometriosis or a proliferation of endometrial tissue in monkeys, mice, and rats.
In humans, the evidence is less clear, but one small study found higher levels of PCBs in infertile women with endometriosis than in infertile women without the disease.
Researchers have also found a decrease in the number of male babies born in Seveso, Itally, since 1976 when there was an explosion at a chemical plant making chlorinated pesticides. The accidental explosion sent a plume of dioxin-laced smoke into the sky and the surrounding community of Seveso. Dust and particles of the dioxin-contaminated pesticide fell on people who lived downwind from the explosion. The dioxin killed pets and contaminated the soil.
A study of former Seveso residents compared the ratio of males to females born in Zone A, which was closest to the explosion, and Zone B, which was further away, to ratios elsewhere. Usually, 51 percent of newborns are male and 49 percent are female. But among children of men who lived in Seveso, only 44 percent were male in the years since 1976. And among children of men who were younger than 19 when the explosion occurred, only 38 percent were male. Zone A is still evacuated, 26 years after the explosion.
Q: Does dioxin also cause birth defects?
A: Yes. During the Vietnam War, The U.S. Military used an herbicide called Agent Orange to defoliate the jungles of Southeast Asia. The herbicide is 50 percent 2,4,5-T. Small amounts of dioxin are produced when 2,4,5-T is made, so it’s an unavoidable contaminant. Studies on Vietnam veterans exposed to Agent Orange suggest that their children have an increased risk of spina bifida.
That’s a birth defect that occurs when the neural tube – which develops into the spinal cord – fails to close during the first six weeks of gestation. Children born with spina bifida often lack bowel and bladder control, and many are paralyzed from the waist down or suffer from mental retardation. The evidence that dioxin causes the defect is strong enough that Vietnam veterans are compensated by the U.S. government if their children are born with spina bifida.
In animal studies, dioxin is a powerful teratogen, a substance that causes birth defects. Its teratogenic effects in animals are as dramatic as its carcinogenic effects. It causes different defects in different organs in different species and strains of animals. For example, it causes cleft palate in mice, malformed kidneys in rats, and extra ribs in rabbits.
Q: Does dioxin affect the reproductive system in men as well?
A: Yes. In animal studies, we see decreased testicular size and decreased sperm production. That’s in adult rats who were exposed to dioxins before they were born. Dioxin also lowers testosterone levels in men. We don’t know how dioxin damages the male reproductive system. One theory is that it’s toxic to the male fetus. Another is that it damages the Y chromosome, so sperm with Y chromosomes don’t fertilize eggs.
It’s the Y chromosome that makes a fertilized egg develop into a male.
Q: Does dioxin impair the immune system?
A: Yes. Linda Birnbaum, EPA leading dioxin expert, calls dioxin an “immune modulator,” because it makes the immune systems of animals both under-reactive and overreactive to stimuli. An over-reactive immune system may raise the risk of auto immune diseases like lupus. An under-reactive immune system is less able to respond to an antigenic challenge – that is, it makes vaccines less effective and leaves the animal less able to fight off infections and possibly diseases like cancer.
The evidence in humans is limited. But after the residents of Quail Run, Missouri, were exposed to dioxin-contaminated oil and debris from Agent Orange manufacturing plants, they had a large number of welts on a skin-prick test, which is designed to detect allergies. That meant that they were allergic to many things–it’s a sign of an over-reactive immune system – though the welts diminished over time.
Q: Does dioxin cause diabetes?
A: The risk of diabetes seems to be elevated in the Ranch Hands group of Air Force troops who had the job of spraying Agent Orange in Vietnam. Researchers compared these Ranch Hand soldiers to other Ranch Hands who weren’t exposed to Agent Orange who had dioxin levels that were similar to most Americans. They found that those with higher dioxin levels – within the normal range – had a higher risk of diabetes than those with lower dioxin levels.
Q: Which of dioxin’s adverse effects are conclusive?
A: Most scientific groups that have evaluated the cancer evidence for dioxin agree that dioxin is a human carcinogen. The studies on veterans are strong enough that they get compensated if their children are born with diabetes or spina bifida. We have animal evidence for developmental delays and reproductive hormonal effects. The human evidence is not as strong for endometriosis and immunotoxic effects.

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