March 25, 2021 - 4:05pm

Is the human race in danger of extinction? That’s the jaw-dropping claim made in Professor Shanna Swan’s new book ‘Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race’. According to the book, sperm counts have dropped almost 60% since 1973 and suggests that they could reach zero by 2045, which would mean no more reproduction and no more babies.

Our Science Editor Tom Chivers wasn’t overly convinced by the thesis, but we wanted to hear Dr Swan out. She argues that chemicals such as “Pthalates”, to be found in everything from ATM receipts to Tupperware plastic, are altering —and endangering — human sexual development, which is getting worse by the year.

Having devoted over 20 years of her career to the study of sperm, the epidemiologist is about as well-credentialed as they come and she is certainly worth listening to. We thank prof Swan for her time and hope you enjoy the discussion. Key quotes below:

On plummeting sperm count:

What we found was that sperm count climbed dramatically over the preceding 40 years, and was at a point where nearly half of men would be entering a range of sperm count that is associated with sub-fertility at least. We didn’t see any indication that the slope of that line had levelled off, so that when we looked at the data restricting it to the past 30 years, 20 years, 10 years, you might hope that it would be flattening out, but we didn’t see any indication of that. That is alarming, because if it were to continue on its present course — that’s a difficult thing to project — but just mathematically… it does hit zero in 2045. So that’s the median sperm count, that means half of men would have no sperm.
- Prof Shanna Swan, LockdownTV

On declining population figures:

It is true that the being below replacement, the value of 2.1 children per couple, is more common in Western countries. And in Asian countries, that’s where it’s most severe. The lowest point I believe, has been reached at 1.0 children in Korea, just recently. But, that’s the rate of decline. Since 1960, the most populous countries…are also declining, and declining faster. So it’s going on everywhere and it’s a problem.
- Prof Shanna Swan, LockdownTV

On phthalates (a group of chemicals):

Phthalates are interesting because they have the ability to lower testosterone. They’re called anti-androgens: they lower the androgens and testosterone is one of those. And so if the pregnant woman is exposed to phthalates in early pregnancy, these phthalates can reduce foetal testosterone at a critical time for male genital sexual development. This was first shown in rodents, and it was so striking that it was named the phthalate syndrome.
- Prof Shanna Swan, LockdownTV

On where these chemicals are found:

These chemicals affect the body’s hormones. Phthalates affect androgens, and bisphenols, which makes plastic hard and they also line tin cans — these are oestrogenic, which also affects reproductive function. There are other chemicals; for instance, we showed in our study that men with exposure higher levels of pesticides, in mid Missouri had much poor semen quality. Other chemicals are in flame retardants in your Teflon pan, in lots of things in your home, your wall coverings and floor coverings. And food is a really major source.
- Prof Shanna Swan, LockdownTV

On increases in gender fluidity:

It feels like there’s an increase, but we don’t have that data. So in the past it could have been there and completely unrecognised and un-talked about. What we do say is that disorders of sexual development, the actual alterations in the genitals — those are caused by environmental chemicals. And there’s many examples of that in rodents, fish, and frogs. So many species have, for example, ovaries and testicles in the same organism, right? So there’s no question that chemicals can change and make these developments atypical, but what the animals would prefer, what gender they would choose, if they could — how would we know that?
- Prof Shanna Swan, LockdownTV

On how to limit chemical exposure:

You could choose products that are stored in glass. And I would recommend that you not store them in your home in plastics. And certainly you do not heat them in plastics. Heat and plastic is a really bad no, no.
- Prof Shanna Swan, LockdownTV