Has male sperm count fallen since 1950?

Kat Arney put this question to Dr Chris Smith... Kat - Chris Smith, you're a medical doctor. How much has the sperm count been declined by since the 1950s? And do we know why?

Chris - This story originates from a study by the Danes in the early 90's and they compared sperm counts collected around the time of the Second World War with contemporary sperm counts, and they reckoned there had been a 50% decline in the samples they were looking at. A subsequent French study, coming about a decade later, suggested that not quite 50% but there was a similar big reduction in sperm counts. Some studies in Italy bucked the trend and they didn't find any decrease in their population but then the Italians, they like to be a little bit different don't they, the Italians. So, on average, we think there might be something in this. Also, if we look in the animal world, we see that there are reports of fish in waterways being exposed to human hormones and also other chemicals changing sex and we can see male fish developing female sexual characteristics. We've also got studies of shellfish on beaches, which have been exposed to sewage outflows and you see some of these shellfish developing some other evidence of being sort of transgender.

Now this appears to be because of exposure to various hormones and things. The evidence for that is that, between about the 1950s and the 1970s, there was a trend to give women after they had babies or while they were pregnant a chemical called diethylbestrol (DES). This was a synthetic form of oestrogen and it was done to do various things, including reduce the amount of milk that the breasts made to avoid mammary engorgement which could be uncomfortable. But when those women had children grew up and they looked at those children, some of those children had genital abnormalities, if they were boys. And this suggested that if you were exposed as a boy during development to oestrogen or oestrogenic-like chemicals, it can have consequences for your fertility. So, what the scientists are speculating is that we don't know why, but there may well be sources of oestrogen-like chemicals coming at us from the environment. Tests on drinking water don't show the levels are very high in Britain - that's not necessarily true in other countries. But certainly food, because of the exposure to animals to the environment they live in, the packaging of food - plastic is in lots and lots of packaging and plastics do release chemicals that can have molecules in them that look like the oestrogen molecule, and they can bind onto the receptor that oestrogen would stimulate - that could well be having this effect.

So the jury is out. We think that the effect and the observed effect is real. We don't know the chemical reason exactly, but we suspect some kind of environmental exposure that everyone is succumbing to because we are living in this world where these plastics are ubiquitous.

Kat - Have we still got Tim on the line. Does that answer your question Tim?

Tim - Yes. Fascinating, yes. I shall go and make sure that my cheese is packed very carefully in the fridge.

Kat - I think the safest thing to do is just eat it all. That would be my scientific advice. Thank you very much for calling in.

Tim - Okay. It was very interesting. Thanks, bye.