Scientists warn of chemical threat to birth rates

FALLING sperm counts could be caused by chemicals used in plastic water bottles and cans as well as traces of the contraceptive pill in drinking water, a new study has warned.

The sex hormone oestradiol, a birth control hormone that passes untreated through sewage plants, has an even larger effect on sperm than Bisphenol A (BPA) found in bottles and food containers.

And scientists warn poor sperm counts are getting worse through the generations and threaten to create a perfect storm for human fertility rates.

Washington State University geneticists have found a direct link between BPA and disrupted sperm production.

The chemical disrupts the delicate DNA interactions needed to create sperm that could account for decreased sperm counts seen in several human studies.

However, the study also bolsters the “oestrogen hypothesis” that oestrogen disruptors in the environment are at play in damaging male fertility.

Dr Pat Hunt said: “This provides some real insight into what exactly might be going on. It’s kind of bizarre because we got into it through a back door, not really starting out to look at that question.”

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Since the early 1990s, when Danish researchers reported “a genuine decline in semen quality over the past 50 years”, with possible implications for male fertility, studies have tried to find out why this was happening.

Sperm count studies have often been criticised for being small, having biased populations or questionable statistical methods, but reproductive biologists continue to see data suggesting that endocrine disruptors like BPA and oestradiol are impairing reproduction.

In a 2013 study, French researchers looked at the partners of more than 26,000 infertile women and saw their semen concentration drop nearly 2 per cent a year for 17 years.

In the study, published in the journal PLOS Genetics scientists gave newborn male mice oral doses of BPA and also exposed mice to the synthetic oestrogen ethinyl estradiol. The researchers exposed the developing testis and saw that the sperm of exposed animals did a poorer job of meiosis, the process in which cells combine the genetic information of their parents. As a result, more sperm died.

Dr Hunt said: “[In] just a few days we permanently change the way that the testis makes sperm in the adult.”

He added: “This mouse model would suggest that here’s actually a reason why these sperm counts would be falling. 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.

“We’ve seen effects over several decades. Infertility is becoming more common. Are we creating the perfect storm?”