Exposure to 'forever chemicals' during first trimester could lower sons' sperm count

Lower sperm count, quality and motility in young men may be associated with their mothers' exposure to 'forever chemicals' in the first trimester of pregnancy.

These chemicals, also known as per-and polyfluoroalkyl substances (PFAS), are a group of over 9000 compounds used in industry to coat certain products to make them water, stain, and heat resistant. Given that they do not naturally break down, PFAS have been found to accumulate over time in the human body and in the water and soil. They have also been linked with various serious diseases, such as cancer and are able to cross the placental barrier from mother to child, therefore putting fetal development at risk.

'A man's reproductive capacity is largely defined in the first trimester of pregnancy when the testicles are developed' Dr Sandra Søgaard Tøttenborg who led the study at the Copenhagen University Hospital said. 'It makes sense that exposure to substances that mimic and interfere with the hormones involved in this delicate process can disrupt normal development and have consequence for semen quality later in life.'

The study, published in Environmental Health Perspectives, recruited 864 men from the Danish Fetal Programming of Semen Quality cohort who were born between 1998 and 2003 and whose mothers provided blood to the Danish National Biobank in the first trimester of pregnancy. After taking semen and blood samples from all participants, the researchers analysed semen quality, testicular volume, and levels of reproductive hormones, such as testosterone. In the meantime, the biobank-stored blood samples from the participants' mothers were screened for 15 different PFAS, of which seven were further analysed together as their levels were above the limit of detection in 80 percent of all maternal samples.

Dr Søgaard Tøttenborg's team found a statistically significant association between mothers with higher levels of combined PFAS exposure and sons with lower total sperm count (ten percent reduction) and sperm concentration (eight percent reduction) as well as a higher proportion of immobile and nonprogressive sperm (five percent increase) in adulthood – which are all key factors contributing to infertility.

'The associations were statistically significant' highlighted Dr Søgaard Tøttenborg. 'The findings indicate that early PFAS exposure may contribute to explain the high prevalence of poor semen quality we are seeing today.'

Although they considered confounders such as maternal age and alcohol consumption during analysis, Dr Søgaard Tøttenborg and colleagues pointed out that comparing multiple associations and different PFAS combinations using the same data could increase the risk of generating significant results by coincidence. Furthermore, it is important to remember that plasma concentrations and semen quality vary significantly across the day in a single individual.

Dr Søgaard Tøttenborg concluded that 'results from epidemiological studies like this one cannot be used to say anything about individual risk, but from a public health perspective, even small changes in reproductive capacity can have a big effect – especially when so many people are exposed.'