A TOILETRIES ingredient has been found to produce "feminising" effects that might contribute to the drastic decline in sperm counts and the increase in male reproductive disorders.
A study on a group of chemicals used as preservatives in products such as skin creams and deodorants has found that the substances can cause adverse effects when injected under the skin of laboratory animals even though the additives have long been approved for use.
Scientists believe the preservatives, known as parabens, can be absorbed through the skin of pregnant women where they might act as an alien female hormone in the womb. This could impair the normal development of a male foetus and so result in fertility problems in later life.
More research is needed to measure doses in people to see if these are similar to those used in the animal experiments. If human exposure is significant, the findings may help to explain why sperm counts have fallen by half over the past 50 years with a significant increase in testicular cancer and other reproductive disorders, such as undescended testes and malformed penises in men, and breast cancer in women.
Professor John Sumpter, an expert on oestrogenic chemicals in the environment and a researcher at Brunel University, said the results could be significant because of the widespread use of the parabens chemicals over several decades by the cosmetics industry.
"We've discovered a new group of chemicals that are weak oestrogens, which have not been reported to be oestrogens before," Professor Sumpter said.
"There is a tremendous amount of concern about falling sperm counts and increases in breast cancer which might result from exposure to oestrogens," he added.
The research, to be published in the next issue of the journal Toxicology and Applied Pharmacology, measured the oestrogenic activity of parabens preservatives using two standard techniques - an in vitro test on genetically engineered yeast and an in vivo test on laboratory rats.
Professor Sumpter said that although the parabens chemicals were found to be several thousand times less potent than oestrogen produced by ovaries, their ability to mimic the female hormone suggests their safety should be reassessed.
More than 13,000 products registered with the American Food and Drug Administration contain parabens. A survey of 215 cosmetics found that 99 per cent of those designed to be left on the skin contained parabens.
In Britain, various items sold in chemists contain at least one type of paraben, including sunblocks for babies and skin cream for stretch marks in pregnant women.
A spokesman for Colipa, the European cosmetics industry association based in Brussels, which has seen the research, said: "There is not a serious risk or concern about the safety of parabens."
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