A report in Europe's leading reproductive medicine journal Human Reproduction concludes that exposure to lead damages sperm function and may be a contributory cause of unexplained male infertility.
The findings have led principal investigator Dr Susan Benoff to urge doctors to measure lead in seminal plasma when evaluating men from couples with unexplained fertility. She also believes there is a case for health and safety authorities to continue re-evaluating environmental exposure limits.
Dr Benoff, director of the Fertility Research Laboratories at the North Shore-Long Island Jewish Research Institute in Manhasset, New York, and colleagues from several other US institutions, undertook a prospective, double-blind study of metal ion levels and sperm function in semen from the partners of 140 consecutive women undergoing their first IVF cycle.
They found that lead levels in seminal plasma varied over a wide range and there was a significant association between high lead levels and a low fertilisation rates, with changes in lead levels accounting for a fifth of the variance in fertilisation rates.
"From our tests on lead in the seminal plasma of the participants and control experiments on nine fertile donors, we have evidence that higher lead levels interfere both with the ability of the sperm to bind to the egg and with its ability to fertilise the egg," said Dr Benoff.
In order to fertilise an egg, a sperm has first to bind to it. A sugar called mannose on the outer coating of the egg is crucial to binding. Mannose receptors located on the head of human sperm recognise the mannose on the coating of the egg and regulate the binding process.
Then the sperm has to penetrate the egg. Successful binding induces an event called mannose-induced acrosome reaction the release of
Contact: Margaret Willson
European Society for Human Reproduction and Embryology