By Peter Montague In 1978, a small group of biologists studying the Elevenmile Creek in Escandia County, Florida, were "startled" to find a population of tiny mosquitofish that all appeared to be males, even though some were pregnant and were bearing normal offspring. Somehow the female mosquitofish had been changed to look like males; they had been "masculinised." Mosquitofish are a small, minnow-like species. In normal mosquitofish, the difference between males and females is obvious. For one thing, males are about half the size of females. For another, males have a long specialised rear fin (called a gonopodium) that females lack, which the males use to insert semen into females. A few days after a female becomes fertilised, a dark spot appears on each side of her abdomen and the spot grows as pregnancy proceeds. Thus under normal circumstances, it is easy to tell male and female mosquitofish apart. But in the Elevenmile River in 1978, the mosquitofish all had a male's gonopodium — even the pregnant females with the telltale spot. Furthermore, the female mosquitofish with a gonopodium behaved like males. They tried to copulate with other females. Further study revealed that a few members of the masculinised population were fully hermaphroditic — having sex organs of both male and female in a single individual. In 1981, a population of mosquitofish on the Fenholloway River in Florida was discovered with the same odd sexual characteristics. During the past 100 years, ichthyologists have collected and examined thousands of specimens of mosquitofish, and no report has appeared of masculinisation, hermaphroditism, or sex reversal. Yet here in two rivers in the Florida panhandle were entire populations with this extraordinary physical change. The cause was easy to find. Both rivers received enormous, dark-coloured discharges from paper mills, discharges about equal to the entire flow of the rivers (25 million gallons per day (MGD) (95 million litres) in the Elevenmile, and 50 MGD in the Fenholloway). Examining fish above and below these discharge points revealed that fish above were all normal and fish below were all masculinised. But what in the paper mill waste was causing the problems? Paper mill waste contains between 250 and 300 chemicals, including dissolved organics, methanol, turpenes, acetone, fatty acids, cellulose decomposition products, lignins and tannins, sulphides, mercaptans, resin-acids, soaps, chlorine and caustic soda. Looking into the problem, researchers found studies dating from 1940 and 1941 in which mosquitofish had been masculinised by exposure to testosterone, the most common male sex hormone. So they reasoned that something in the paper mill waste was probably acting like a male sex hormone. But what? This problem has been a scientific political football for 15 years. Two parallel tracks of research have been proceeding: dioxin and chlorinated chemicals have been investigated, and naturally occurring hormone-mimicking chemicals from plants (phyto-oestrogens) have been investigated.
Dioxin research
By 1970, there were many reports circulating which linked dioxin to various human reproductive problems, chiefly birth defects. In 1980, the US Environmental Protection Agency (EPA) discovered dioxins and furans in paper mill waste. In 1983, dioxin was found in fish living downstream from paper mills. This was not a welcome finding. The volume of paper mill wastes is huge: in the 1980s, each ton of pulp produced about 25,000 gallons of contaminated waste water from the chlorine-bleaching process. With 73 million tons of paper products produced in 1986, bleaching wastes totalled approximately 1.83 trillion gallons of chlorinated gunk per year — a total waste flow of 219 cubic metres per second. This flow is larger than some major rivers. In addition to being immensely wasteful, the paper industry is politically very powerful, with 674,000 people employed (a 1986 figure) and US mills producing products valued at US$3.9 billion each year. This powerful force has spent untold millions diverting attention from its dioxin-laden discharges. During the early Reagan years, top EPA officials did their part to prevent recognition of the dioxin problem; EPA chief Anne Burford and her assistant, Rita Lavelle, were eventually fired for dioxin-related shenanigans, and Burford's successor, John Hernandez, resigned in disgrace after Congress investigated his role in the altering of a report on dioxin in the Great Lakes. Congress then appropriated $4 million for a nationwide study of dioxin in the environment. Preliminary data from that study, available in 1985, clearly implicated pulp and paper mills in dioxin contamination of waterways in Minnesota and Maine, and of fish living downstream from paper mills. Paper industry officials muscled EPA chief William Reilly in early 1991, persuading him to initiate a multi-year "scientific reassessment" of dioxin, which EPA promptly got under way in April 1991, and which the agency has still not concluded. During the course of that "reassessment", information has come to light showing beyond any doubt that dioxin mimics hormones and disrupts the endocrine (reproductive) system of fish, birds, mammals and most likely humans as well.Natural phyto-oestrogens
Thee other line of research proceeded in a less politically charged atmosphere. Scientists had first reported naturally occurring hormone-mimicking chemicals in plants (phyto-oestrogens) in 1948, when female sheep became sterile after grazing on clover pastures for prolonged periods in Australia. In 1976, researchers in California had shown that certain desert plants in dry years produce chemicals that inhibit reproduction in the California quail. In 1979, it was shown that a common oestrogen-mimicking chemical in woody plants — beta-sitosterol — could affect the reproductive system of rabbits. By the mid-1980s, researchers demonstrated similar effects of beta-sitosterol on mice and rats. In 1991, studies of paper mill effluent began to multiply, many of them by Canadian researcher Glen Van Der Kraak. Van Der Kraak and his colleagues have shown that some wild fish living downstream from pulp and paper mills reach sexual maturity much later than normal. Other species such as the lake whitefish can be sterilised by living below a pulp mill. Others have exceptionally small reproductive organs and abnormally low levels of sex hormones in the blood. In 1995, Van Der Kraak pointed out that pulp mill waste contains 280 to 1200 parts per billion (ppb) of beta-sitosterol, from the bark of the trees being turned into pulp. It is the same beta-sitosterol that has been shown to affect the reproductive systems of rabbits, mice, rats, and sheep. Furthermore, in 1995 Van Der Kraak injected goldfish with beta-sitosterol and showed that the levels of sex hormones in their blood were significantly altered. Industry is already arguing that synthetic chemicals couldn't possibly be affecting sexual reproduction and development in wildlife and humans, as many scientists now believe they are. No doubt, Van Der Kraak's 1995 goldfish study, emphasising the role of naturally occurring compounds, will become ammunition for those who need a rationale for continuing to poison wildlife and people with synthetic chlorine compounds. However, even Van Der Kraak doesn't believe naturally occurring phyto-oestrogens explain all the problems seen in wildlife exposed to paper mill wastes. "I don't think beta-sitosterol is going to explain the entire picture", Van Der Kraak told Janet Raloff of Science News. Fish downstream from pulp mills frequently exhibit detoxifying liver enzymes, "and we're not seeing that with beta-sitosterol", he says. "So there must be other chemicals the fish are exposed to — such as some chlorinated organics — [activating] those enzymes." In other words, the trail once again leads back to dioxin and other chlorine-containing wastes.[From Rachel's Environment & Health Weekly.]