Common chemicals can reduce male fertility

Everyday substances in the environment directly affect the ability of sperm to fertilise an egg by triggering the premature release of a chemical cocktail that sperm cells use to penetrate the egg's outer layer, a study has found.

The findings could explain how environmental chemicals found in a range of substances from industrial and domestic products to ordinary food and drink can mimic the female hormones that affect male fertility.

Lynn Fraser, professor of reproductive biology at King's College London, said the results demonstrated a possible mechanism for how environmental oestrogens – known as endocrine disrupters – could directly affect the normal functions of a sperm cell.

"Our study is the first to provide both indirect and direct evidence that natural and environmental oestrogens significantly affect sperm fertilising ability," Professor Fraser told the European Society of Human Reproduction and Embryology in Vienna.

"These findings could be important in understanding how different compounds, known to be present in our environment, might affect sperm function in humans. Given that the environmental oestrogens are very potent and that we are probably being exposed to several at the same time, it is important to know whether they might have cumulative effects," Professor Fraser said.

The study compared three environmental oestrogens found in soya beans, peas, hops and some industrial products such as cleaners, with a natural oestrogen present in the vagina as well as semen.

The scientists investigated how each of the four substances affected the release of the packet of enzymes stored in the head of mouse sperm, which are used to penetrate the protective barriers surrounding the egg.

The environmental oestrogens stimulate the release of the sperm's egg-penetrating cocktailbefore they actually make contact with an egg.