Dioxin: more dangerous than we thought

November 7, 1995
Issue 

By Peter Montague The word "dioxin" stands for a group of chemicals that occurs rarely, if ever, in nature. A very large proportion of dioxin comes from human sources. Dioxin began accumulating in the environment around 1900 when the founder of Dow Chemical invented a way to split table salt into sodium atoms and chlorine atoms, thus making large quantities of "free (chemically unattached) chlorine" available for the first time. Initially, Dow considered free chlorine a useless and dangerous waste. But soon a way was found to turn this waste into a useful product by attaching chlorine atoms onto petroleum hydrocarbons, thus creating, during the 1930s and 1940s, a vast array of chlorinated hydrocarbons. These new chemicals gave rise to many of today's pesticides, solvents, plastics, and so forth. Unfortunately, when these chlorinated hydrocarbons are processed in a chemical plant or burned in an incinerator they release an unwanted by-product, dioxin, the most toxic family of chemicals ever studied. Dioxin is released by paper mills, metal smelters, many chemical plants and pesticide factories, and by all incinerators. According to Greenpeace chemist Pat Costner, the biggest source of dioxin discharges into the environment is factories that make the popular plastic, PVC (polyvinyl chloride). Industry and the US Environmental Protection Agency have known much of the bad news about dioxin since at least the late 1970s, but have done little or nothing about it. In 1991, the paper industry and the Chlorine Council, pressured EPA to relax the few dioxin standards that it had in place at the time. In response, EPA has spent the last four years re-examining the toxicity of dioxin, in preparation for deciding what to do about it. Last year they released a draft "dioxin reassessment" report. So-called "conservatives" in Congress have attacked Chapter 9 of the reassessment — the chapter containing most of the chillingly bad news about dioxin — complaining that it has not been adequately "peer reviewed." Last month the main authors of Chapter 9 published — in a peer-reviewed journal — their own conclusions about the toxicity of dioxin. Their basic message was that dioxin is toxic to humans in surprisingly many ways, and that the general public is not adequately protected from ill effects by a traditional "margin of safety". Public health policy usually aims to keep the public's exposure to poisons to at least 100 times below levels known to harm humans or animals. The new EPA report shows that US adults are already carrying an average dioxin burden in their bodies that is remarkably close to the levels known to cause illness in humans or animals. EPA says the average US 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 (a nanogram is a billionth of a gram) of dioxin per kilogram of body weight (ng/kg). Further, EPA estimates that 5% of Americans — some 12.5 million people —have body burdens twice that average. As the following list of effects of dioxin (as reported by EPA) reveals, an average body burden of 13 ng/kg qualifies as a major public health problem in the US today.

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. Chloracne produces skin eruptions, cysts and pustules — like a very bad case of acne except that the sores can occur all over the body and can last for many years. 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 seven times as high as the body burden of the average person in the US today. In fact, the EPA study cites examples of humans getting chloracne with body burdens only three times as high as the US average.

Cancer

There have been five peer-reviewed studies showing cancer in humans exposed to dioxin through accidents or routine activities at work. These studies 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 there is not even a factor of 10, let alone the 100 aimed for in public health policy, separating the average American from the possibility of cancer from dioxin.

Learning disorders

Laboratory experiments on monkeys (marmosets) reveal learning disabilities in young monkeys with a dioxin body burden as low as 42 ng/kg — only 3.2 times as high as that of the average American.

Decreased testosterone and sperm count

Researchers at the National Institute of Occupational Safety and Health found reduced levels of the male sex hormone testosterone circulating in the blood of dioxin-exposed male workers. The reduction in testosterone levels was statistically significant, but still remained within the range that is considered normal. Other sex hormone levels in these men were also affected. These dioxin-exposed workers had body burdens only 1.3 times the dioxin body burden of the US population. Further, if we can assume that dioxin exposure caused the diminished testosterone levels, then some humans are 280 times as sensitive to dioxin as rats, with regard to testosterone. Male offspring of rats with a body burden only five times as high as the US average also have diminished sperm production. During the last 50 years, sperm production of men throughout the industrialised world has dropped by 50%.

Diabetes

In two studies, an increased incidence of diabetes has been reported in dioxin-exposed Vietnam War veterans. As well, on October 6 Reuters reported on a new 20-year study of Air Force veterans exposed to Agent Orange which shows that dioxin-exposed veterans have an increased incidence of diabetes and heart disease. 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 eight below the lowest level thought to create a diabetes hazard.

Immune system

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 average Americans — display an increased susceptibility to infections by viruses.

Endometriosis

Female rhesus monkeys with body burdens only five times that of the human average in the US have a measurable increase in endometriosis, the painful, debilitating disease of the uterus. Endometriosis is increasing in US women. Dioxin, it is becoming clear, is an astonishingly versatile and potent poison. EPA, and the corporations that release dioxin into the environment, have waffled and fudged the issue for 20 years or more. But 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. What other choice do we have?
[Abridged from Rachel's Environment and Health Weekly, October 12, 1995.]

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