Dioxin is the most toxic man-made organic chemical; its toxicity is second only to radioactive waste. Dioxin is the name generally given to a class of super-toxic chemicals, the chlorinated dioxins and furans, formed as a by-product of the manufacture, molding, or burning of organic chemicals and plastics that contain chlorine.
Dioxin normally occurs as a complex mixture of a family of compounds which vary greatly in toxicity. Sometimes the term dioxin is used to refer only to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most well-studied and the most toxic form of dioxin.
Dioxin exhibits serious health effects when it reaches as little as a few parts per trillion in your body fat. Dioxin is a powerful hormone disrupting chemical. By binding to a cell's hormone receptor, it literally modifies the functioning and genetic mechanism of the cell, causing a wide range of effects, from cancer to reduced immunity to nervous system disorders to miscarriages and birth deformity. Because it literally changes the functioning of your cells, the effects can be very obvious or very subtle. Because it changes gene functions, it can cause so-called genetic diseases to appear, and can interfere with child development. There is no "threshold" dose - the tiniest amount can cause damage, and our bodies have no defense against it.
Bizarre health effects, such as cancer, spina bifida (split spine) and other birth defects, autism, liver disease, endometriosis, reduced immunity, chronic fatigue syndrome, psychological disorders, and other nerve and blood disorders have been reported.
Like the pesticides such as DDT, dioxin accumulates in the fat cells of the animals, and re-appears in meat and milk. Dioxin is virtually indestructible in most environments, and is excreted by the body extremely slowly.
Dioxin is used as a blanket term for a family of chemical compounds that are formed through combustion, chlorine, bleaching and manufacturing processes. The combination of heat and chlorine creates dioxin. Since chlorine is often a part of the earth's environment natural ecological activity, volcanic activity and forest fires can lead to the formation of dioxin. Nevertheless, dioxin, a highly carcinogenic and toxic compound is mostly created by human activity.
The EPA Study ²
All results reported here were taken from peer-reviewed literature and were statistically significant. All of the following information is taken from the new EPA study.
EPA'S LATEST FINDINGS:
EPA says the average U.S. citizen has no particular exposure to dioxin besides what is routinely eaten in food --mainly in red meat, fish, and dairy products. This routine dietary exposure has produced an average body burden that is estimated to be 13 nanograms of dioxin per kilogram of body weight (ng/kg). (A nanogram is a billionth of a gram; a gram is 1/28th of an ounce. A kilogram is about 2.2 pounds.) Ng/kg is equivalent to parts per trillion. So 13 ng/kg seems tiny --and as an absolute quantity it is. But compared to the amount that causes havoc in dioxin-exposed animals and humans, 13 ng/kg qualifies as a major public health problem, in our opinion. (EPA estimates that 5% of Americans --some 12.5 million people --have body burdens twice the average.) Here are some effects of dioxin, as reported by EPA:
CHLORACNE: Chloracne was the first disease associated with exposure to dioxin, first described in 1897. Chloracne appeared as an occupational problem in the 1930s among pesticide workers, and among workers who manufactured industrial chemicals called PCBs [polychlorinated biphenyls]. However, dioxin was not identified as the cause of chloracne until about 1960. (Dioxin was an unwanted contaminant of the pesticides and PCBs.) Chloracne produces skin eruptions, cysts and 'pustules' --like a very bad case of teenage acne, except that the sores can occur all over the body and in serious cases can last for many years. To grasp the nature of a bad case of chloracne, we can recall Dr. Raymond Suskind's description of one of his patients, a white man who got chloracne from dioxin exposure in a Monsanto chemical plant in West Virginia in 1949: "... he has given up all social and athletic functions and remained in his house, according to his own description, for months on end. Several times he has been mistaken for a Negro and forced to conform with the racial segregation customs of the area. This has happened on buses or in the theatres [sic]," Suskind wrote. 
In laboratory animals, chloracne occurs at body burdens as low as 23 ng/kg and as high as 13,900 ng/kg; in humans, chloracne has occurred at body burdens as low as 96 ng/kg and as high as 3000 ng/kg. This means that some humans get chloracne when their dioxin body burden is only 7 times as high as the body burden of the average person in the U.S. today. In other words, there is not even a factor of 10 separating the average person from the possibility of chloracne. In fact, the EPA study cites examples of humans getting chloracne with body burdens only 3 times as high as the U.S. average.
CANCER: There have been 5 peer-reviewed studies showing cancer in humans exposed to dioxin. The exposures occurred through accidents or through routine activities at work. These studies of humans show that, for some human populations, the danger of cancer begins to rise noticeably when the dioxin body burden reaches 109 ng/kg. This means that a cancer effect in humans is evident when the dioxin body burden reaches a point 8 times as high as the average dioxin body burden in the U.S. public. Again, there is not a factor of even 10 separating the average American from the possibility of cancer from dioxin.
BEHAVIORAL EFFECTS & LEARNING DISORDERS:
Laboratory experiments on monkeys (marmosets) reveal learning disabilities in young monkeys with a dioxin body burden as low as 42 ng/kg.  Thus learning disorders are evident in monkeys who have a dioxin body burden only 3.2 times as high as that of the average American. Again, there is not a factor of even 10 separating the average U.S. resident from the possibility of a dioxin effect on the central nervous system.
DECREASED MALE SEX HORMONE:
Researchers at the National Institute of Occupational Safety and Health (NIOSH) found reduced levels of testosterone --male sex hormone --circulating in the blood of dioxin-exposed male workers.  Other sex hormone levels in these men were affected as well. If we can assume that dioxin exposure caused the diminished testosterone levels, then some humans are 280 times as sensitive as rats are, from the viewpoint of testosterone. What seems most important is that these dioxin-exposed workers had body burdens only 1.3 times the dioxin body burden of the U.S. population. Thus there is not even close to a factor of 10 separating the average U.S. male from the testosterone effects seen in dioxin-exposed workers. The reduction in testosterone levels was statistically significant, but the reduction was small and the measured levels still remained within the range that is considered normal.
DIABETES: In two studies, an increased incidence of diabetes has been reported in dioxin-exposed Vietnam veterans; a third study that reaches similar conclusions was reportedly released last week by the U.S. Air Force.  The body burdens that seem to produce an increase in diabetes range from 99 to 140 ng/kg. Thus the average American, with a body burden of 13 ng/kg, is a factor of 8 below the lowest level thought to create a diabetes hazard. Once again, there is not even a factor of 10 separating the general public from the levels though to cause health problems in dioxin-exposed people.
IMMUNE SYSTEM TOXICITY: In monkeys (marmosets), changes in white blood cells associated with the immune system can be measured at dioxin levels of 10 ng/kg --25% below the level already found in average Americans. Mice with body burdens of 10 ng/kg --25% below the amount already found in you and me --display an increased susceptibility to infections by viruses, presumably because their immune system has been damaged.
SPERM LOSS AND ENDOMETRIOSIS. Female rhesus monkeys with body burdens only 5 times as high as the U.S. average have a measurable increase in the painful, debilitating disease of the uterus, called endometriosis. Endometriosis is increasing in U.S. women. (RHWN #364, #377.) Male offspring of rats with a body burden only 5 times as high as the U.S. average have diminished sperm production. During the last 50 years, sperm production of men through the industrialized world has dropped 50%. (RHWN #343, #432.)
CONCLUSION: We have only scratched the surface of the bad news that has accumulated about dioxin. It is an astonishingly versatile and potent poison. EPA, and the corporations that release dioxin into the environment, have waffled and fudged for 20 years or more. The answer to this burgeoning public health problem is clear, if not easy: over the next 20 years, we must ban chlorine as an industrial feed stock and thus cut off the source of all dioxins.
Jonathan Campbell, Health Consultant
43 Boynton Street, S. 2R
Boston, MA 02130-3263 http://www.sqs.com
Michael J. DeVito and others, "Comparisons of Estimated Human Body Burdens of Dioxinlike Chemicals and TCDD Body Burdens in Experimentally Exposed Animals," ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 103, No. 9 (September, 1995), pgs. 820