"This mouse model would suggest that here's actually a reason why these sperm counts would be falling," said Dr Hunt. "We're actually doing something to this process that's going to cause the death of more cells as they're trying to make sperm. They're going to get culled out by this quality-control mechanism and the upshot of that will be that if you do enough of this, you'll drop sperm counts."
BPA is widely used in the lining of food and drink cans, while estradiol passes untreated through sewage plants.
Dr Hunt, whose research is reported in the online journal Public Library of Science Genetics, fears that sperm counts will continue to fall with each exposed generation.
"We've seen effects over the course of several decades," she said. "What about several generations? Infertility is becoming more common. Are we creating the perfect storm?"