Page URL:

Podcast Review: Why Have Sperm Counts More Than Halved in the Past 40 years?

7 June 2021
Appeared in BioNews 1098

We've all been told that smoking, drinking too much and being overweight are bad for our overall health and can have a negative impact on our fertility. Those trying for a baby will often quit drinking alcohol, take up jogging and try to live generally healthier lifestyles in the hopes of improving their chances of conception. 

How would you feel if you found out your everyday household products could be having a negative effect on your fertility?

Dr Shanna Swan is one of the world's leading environmental and reproductive epidemiologists and a professor of environmental medicine and public health at Mount Sinai school of medicine in New York City. She has dedicated her working life to identifying everyday chemicals that are threatening human fertility. 

Dr Swan discussed her research findings in a fascinating podcast interview with Rachel Humphreys for the Guardian. The questions were thoughtful and explorative, and Dr Swan gave answers that were simple enough that any listener could understand without losing any of the key messages. 

Over the past 40 years, average sperm counts have fallen by nearly half. This can be attributed to many factors, but Dr Swan believes that environmental toxins are playing a massive role.

A group of chemicals that Dr Swan thinks are of particular concern are phthalates. She describes phthalates as 'everyday everywhere' chemicals, as they are found in almost all aspects of our lives. They make plastics soft and flexible so are often used to make tubing for practices like food processing and milking. They also help products to retain pigment and scent so are frequently used in cosmetics and perfumes. Phthalates are in our floors, our walls, our furniture. They truly are everywhere.

Why are phthalates so bad?

Phthalates are endocrine-disrupting chemicals. These chemicals interfere with hormones and therefore normal functioning of the endocrine system, which among many other roles within the body, controls sexual function and reproduction.

Unfortunately, phthalates don't stay within the products they are put into. They 'off gas' into the environment, entering the air we breathe and consequently into our bodies too. 

Dr Swan's research has demonstrated that phthalates can interfere with testosterone production, reducing sperm count and increasing the risk of miscarriage and premature birth. How utterly terrifying that items we use everyday without thought could be interfering with our chances of successful conception. 

The most sensitive period for development is during early pregnancy when organs are being formed. The male genital tract requires a certain amount of testosterone to develop correctly. If the fetus comes into contact with high concentrations of phthalates, Dr Swan states that this process can be interrupted. The consequence of this is that the child may not be completely 'masculinised', meaning his genital tract has not formed properly. 

One of the ways that Dr Swan researches the impact of phthalates on males is to measure the 'analgenital distance'. This, as you may have guessed, is the distance between the anus and genitals. If boys are exposed to less testosterone in utero this distance is shorter. A reduced analgenital distance has been linked to reduced sperm counts in adulthood. Dr Swan has measured the phthalate levels in mothers' urine and found a negative correlation with the analgenital distance in boys. This suggests that phthalate exposure during pregnancy could have long-term negative implications for male fertility.

As a woman in my mid-20s who hopes to have children someday, this podcast gave a terrifying insight into the effects that the environment can have on the reproductive systems of ourselves and our children. 

If you're anything like me, you're probably looking around your house anxiously wondering about which items contain phthalates and how you can keep you and your family safe.

The regulation of phthalates differs around the world. Dr Swan points out that the European Union (EU) has stricter rules around phthalate usage than the USA, for example, 11 chemicals are banned in the US, while 1100 are banned in the EU. However, no matter where you live, it's likely that you will come into contact with phthalates on a regular basis.

Dr Swan suggested that to minimise contact as much as possible, we should only be eating unprocessed food. This means no food that comes in a can, a bottle, or a plastic container, as phthalates can be introduced through the container itself or through the food production process.

Unfortunately, I think this recommendation would be unrealistic for the average family to achieve. In a normal supermarket this is how most foodstuffs are packaged and it would be expensive and difficult to source ingredients that are completely packaging-free the whole way along the supply chain. 

In my opinion, a more realistic tip could be to look online to see which skincare and cosmetic items are free from phthalates. A quick Google search will bring up plenty of websites that have lists of companies that do not use phthalates in their products. By switching to phthalate-free beauty products we can decrease direct skin exposure to these chemicals.

Overall, I found this interview with Dr Swan extremely interesting, but also very scary. I had never heard of phthalates before listening to this podcast, but I will definitely be more conscious of them moving forward. I would recommend that anyone who is interested in the effects of environmental toxins on fertility give this podcast a listen. 

Why have sperm counts more than halved in the past 40 years?
The Guardian |  3 May 2021
27 October 2019 - by Dr Katie Howe 
Men who follow a Mediterranean-style diet have higher sperm counts than men who eat unhealthily, according to a small new research study...
30 September 2019 - by Sarah Gregory 
After he had a series of unsatisfactory fertility testing experiences, Mohamed Taha decided to launch his own company Mojo Diagnostics in Lyon, France in an attempt to improve the process of sperm count testing...
9 September 2019 - by Jakki Magowan 
The BBC's World Service weekly podcast series, CrowdScience, invites listeners to pose questions about life, Earth and the universe. To find answers, they interview experts at the frontiers of knowledge...
3 December 2018 - by Georgia Everett 
Men who smoked while their partners were pregnant have sons with lower sperm counts, according to a study in Sweden...
to add a Comment.

By posting a comment you agree to abide by the BioNews terms and conditions

Syndicate this story - click here to enquire about using this story.