Studies highlight chemical threats to reproduction

BMJ 1995; 311 doi: (Published 05 August 1995) Cite this as: BMJ 1995;311:347

Two major studies released last week have once again focused attention on the potential effects of manmade chemicals on the reproductive systems of humans and wildlife. Research commissioned by the Department of the Environment and carried out by Brunel University has largely laid to rest fears that Britain's drinking water is contaminated with oestrogenic chemicals. But the research has shown that untreated river water, particularly near sewage outlets, can have feminising effects on male fish.

The department has also published a report compiled by the Medical Research Council's Institute for Environment and Health which provides a general overview of current knowledge on the subject. It shows gaps in our understanding of human reproductive systems and the effects of pollution on fertility and sexual development.

It is now generally accepted that the Western world at least has witnessed a considerable decline in the quality of human sperm this century, coupled with a rise in malformation of the genitals and an increase in rates of testicular and breast cancers. Experiments on animals have repeatedly shown that artificial oestrogens such as those found in the pesticide dicophane (DDT) can lead to these symptoms.

No causal link has been found, however, to prove that environmental oestrogens have damaged men's reproductive ability, and the authors of the Medical Research Council's report agree with the government that further study is needed before any chemicals are banned. With 3000 chemicals in food and the environment suspected of mimicking oestrogenic properties, progress is likely to be slow.

The Brunel report seems to confirm the theory that food, not water, is the main risk area for oestrogens. Male fish left in cages near sewage outlets produced the protein vitellogenin, normally found only in females, and showed smaller testicle growth than controls. Treated drinking water, however, had no measurable effect on masculinity. The likely culprits in rivers are alkyl phenol ethoxylates and nonylphenol ethoxylates widely used in industrial detergents, paints, and pesticides as surfactants.

The vast range of hormonally active chemicals present in the environment has produced a variety of “gender bending” effects among wildlife. Alligators in Lake Apopka, Florida, the scene of a major spill of a component of dicophane, have been dramatically demasculinised, with smaller penises and higher mortality among the young. Conversely, female molluscs in the North Sea and other places suffer from imposex, with small penises growing adjacent to their normal organs. This is believed to be associated with tributyltin contamination in marinas.

Environmentalists have criticised the government's cautious approach to the issue. Kerry Rankin of the environmental pressure group Greenpeace said: “We already know several groups of chemicals which have endocrine disrupting effects. It seems ludicrous not to act on these now—it's not as if they are going to be proved safe after all. It's true we need further research, but let's concentrate on the things we don't understand. With the sperm count dropping at 2% a year, we don't necessarily have all the time in the world.”—OWEN DYER, freelance journalist, London

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