the first direct evidence of a link between exposure to environmental estrogens and low male fertility has been found by researchers from the London-based King's College. Environmental estrogens are chemicals found in the environment that mimic biological estrogen present in female sex hormones.

The researchers investigated how three environmental estrogens and one biological estrogen affected the sperm development in a mouse. This stage, known as capacitation, is when the sperm acquires the ability to fertilise an egg. It was found that though all the estrogens accelerated the development of immature sperm towards full fertility, the three environmental estrogens rendered fully mature sperm incapable of fertilising an egg. This is because they stimulated the sperm to undergo the acrosome reaction