s/r home | issues | authors | 7-8 contents
Why Is Dioxin So Dangerous?
byby Don Fitz, Gateway Green Alliance
# section What Are Dioxins? (below)
Diseases which have been linked to dioxin seem endless. Research has shown that it causes skin disfiguration, Hodgkin's disease, non-Hodgkin's lymphoma, soft-tissue sarcoma, leukemia, liver cancer, and porphyia cutanea tarda (PCT, a metabolic disorder).
Ingesting dioxin can also result in congenital malformations, spontaneous abortions, and a slow wasting syndrom followed by death similar to the AIDS syndrome. Dioxin is strongly suspected of contributing to pathology of the urinary and hematological systems, growths in the colon, gall bladder complications, multiple myeloma, and lung, larynx and prostate cancer.
According to researcher Joe Thornton, "Dioxin's health effects include endocrine disruption, reproductive impairment, infertility, birth defects, lowered sperm counts, impaired neurological development, damage to the kidneys, and metabolic dysfunction...There is no evidence that there is a safe level of dioxin exposure below which none of these effects will occur..."
Why does dioxin have so many different effects? And why do some diseases show up in some investigations but not others?
Dioxin is an organochlorine, or a man-made chemical which has chlorine bound to organic compounds. Organochlorines are foreign to the biology of life. They are not created naturally in the bodies of humans or other terrestrial animals. This is because living tissue must be able to easily break down or biodegrade. Organochlorines are extremely stable, sometimes taking hundreds of years to break down.
When dioxin is taken into the cell nucleus, it works like a "turn on" valve which begins the production of enzymes. Enzymes cause a vast amount of bodily activity. The huge number of enzymes do two things: start and stop biological activity. Much activity is stopped by the enzyme biodegrading. But the organochlorines degrade very slowly (estimated half-life of 7 to 12 years). Thus, dioxin functions like a permanent "on" switch which keeps a particular bodily process going.
Many toxic chemicals are linked with a specific illness, such as lead and brain damage or asbestos and mesotholioma. Others are linked with several illnesses. Dioxin is tied to such a very large number of diseases because it is a cancer-enhancer. Dioxins intensify cancers which other toxics begin.
As Barry Commoner explains, "...dioxin greatly enhances the activity of the enzyme system that converts most environmental carcinogens into active agents. Apparently, dioxin can so powerfully stimulate the enzyme as to sharply increase the activity of the small amounts of carcinogens present in...food, water, and air and thereby intensify their effect on tumor incidence. In effect, dioxin influences tumor production by enhancing the activity of carcinogens..."
This is why dioxin has totally different effects on different people. If a group of workers has already been exposed to chemicals which cause Hodgkins disease, dioxin will speed up the process and research will show that they have an increased rate of Hodgkin's disease. If a community has been exposed to chemicals which cause leukemia, dioxin will increase the rate of leukemia.
On the other hand, if dioxin is spread on a group of people who have come into contact with a variety of pollutants (because they have different kinds of jobs), then there would be very small increases in many diseases. The only way researchers could measure the effects would be to add a long list of diseases and compare their total frequency in a group which was exposed and another group which was not exposed. This is similar to what Marilyn Fingerhut and other researchers did when they found that combined cancers had a 46% higher likelihood of occurring amongst workers who had been exposed for a full year (and after a 20 year "latency" period had elapsed).
The problem with doing research like this is finding a group of "unexposed" people to use for comparison. There used to be virtually no dioxin in human tissue. This changed during the 1930s, when industry began producing large amounts of organochlorines such as insecticides, fungicides and chemical fertilizers. Their production mushroomed after World War II. Never intentionally created, dioxin is a by-product of the manufacture of agricultural chemicals, bleaching in paper and pulp mills, and incineration. Dioxin is formed after gases leave the incinerator's stack.
As a result, the organochlorine industry produces an estimated 1200 pounds of dioxin in the US each year. To get an idea of the magnitude of this threat, it was considered a major disaster when an explosion spewed 1 to 4 pounds of dioxin into the air over Seveso, Italy in 1976. Studies are now showing a broad range of cancers in the people. According to chemist Pat Costner, "The 12 pounds of dioxin produced each year by the pulp and paper industry is enough for a lifetime dose for 500 million people."
Medical researcher Arnold Schecter reported that tissue samples "taken from Eskimos who were frozen in an ice floe 100 to 400 years ago was recently found to have extremely low levels of dioxins." The typical adult male in the US now averages 26 molecules of dioxin in the cells of his body.
What Are Dioxins?Carbon exists both as an element (graphite and diamonds) and as a compound (bound with other elements). The study of compounds which include carbon (abbreviated "C") is known as organic chemistry. Carbon binds with hydrogen (abbreviated "H") in thousands of ways, sometimes in long strings which form plastics. The 2.5 million carbon compounds are more than all other compounds combined.
Compounds with carbon and hydrogen can also form rings. The most infamous carbon ring is benzene, which is a ring of six carbon atoms, each with a hydrogen atom on the outside. Benzene is so important to organic chemistry that it has its own symbol of a ring inside of a hexagon. In this drawing, single lines indicate a "bond" of atoms sharing an electron; double lines indicate the atoms share two electrons:
Benzene rings have two important properties:
1. Two or more benzene rings can themselves bind together; and,
2. Chlorine can replace hydrogen on the outside of the ring.These principles explain the formation of the very toxic families of PCBs, furans and dioxins. A pair of benzene rings joined together forms biphenyl:
If chlorine is present when benzene is burned (and there is plenty of chlorine in plastics), hydrogen atoms can be released and chlorine atoms can replace them. The result is poly-chlorinated biphenyls, knows as PCBs. Their production was banned in the 1970's.
If oxygen (abbreviated "O") forms another link between the two benzene rings the result is furans. If chlorine replaces hydrogen atoms, the furans are also very toxic:
Sometimes benzene molecules bind together with two oxygen atoms, with the resulting name of dioxin. Unlike furans, dioxins are symmetrical (the same at the top and bottom).
Since 2 oxygen atoms bind 2 benzene molecules, the chemical name is dibenzo dioxin. The abbreviation PCDD means polychlorinated dibenzo dioxin, which occurs when chlorine atoms replace hydrogen. Dioxins can have 1 to 8 chlorine atoms. The 75 different types of chlorinated dioxins result from the positions where chlorine atoms occur. This is so crucial in determining characteristics of the dioxin (such as how poisonous it is) that chemists use numbers to describe the positions of the chlorine atoms. The most deadly form of dioxin has chlorine in the 2, 3, 7 and 8 positions:
Using the word tetra (for "four"), chemists named this molecule "2,3,7,8 tetra-chloro dibenzo dioxin," or 2,3,7,8 TCDD. The molecule is perfectly symmetrical.
The presence of chlorine makes dioxins extremely stable compounds. They do not break down as easily as enzymes do. The human body tends to store dioxin in adipose (fatty) tissue. When people take in dioxin through food or air, it ends up inside of their cells. This is due to Ah receptors, which move some molecules to cells' interior. Ah receptors match the shape of 2,3,7,8 TCDD very closely. Other dioxins and furans have many of the same effects as 2,3,7,8 TCDD, but are less deadly because they are less symmetrical and do not fit the Ah receptor as well.
The toxic equivalency (TE or TEQ) of an organochlorine is a measure of how toxic it is relative to 2,3,7,8 TCDD. An organochlorine with a TEQ of .05 is 5% as poisonous as 2,3,7,8 TCDD.