Air pollution linked to reduced sperm quality

Infertility (the inability to conceive following a year of unprotected sex) affects 14% of couples in the UK. Men are often overlooked during the fertility/conception journey, yet male factor infertility accounts for around 50% of infertility cases. Evidence has shown that sperm quality has been decreasing over the 21st century. Explanations behind the decline are not fully understood but there is a growing belief that environmental factors are having a huge impact. 

Air pollution is a notable risk factor for increasing morbidity, particularly particulate matter (PM) over gaseous components. Incidents such as the London smog in 1952 (an extreme example as PM was estimated to be at very high concentrations) directly led to 4,000 deaths and 100,000 suffering adverse health effects. Even so, air pollution exposure is expected to double by 2050.   

A recent study emerging in JAMA Network has found an association between PM air pollution and reduced sperm motility. 

The research team retrospectively analysed semen parameters (sperm motility, count, concentration) using samples from 33876 men, an impressively large sample size. The men were pursuing assisted reproductive procedures with their wives. They found associated exposure to PM reduced sperm motility but had no significant effect on sperm count and concentration.  

Evaluation of PM size showed exposure to fine PM during sperm development had the greatest motility reduction effect compared to medium and large PM. A second condemning factor found was the timing of PM exposure during sperm development. Exposure, and thus disruption, during earlier stages of development had the largest impact on sperm motility. It was hypothesised that early exposure may affect gene expression mechanisms. 

Despite limitations of this study, such as unaccounted confounders to sperm quality (obesity and smoking), the evidence put forward is alarming. The study has provided emphasis on the importance of environmental health and the growing need to reduce the impact of air pollution. It is yet to be determined whether public health interventions or larger individual efforts are needed to reduce this impact. However, the imminent threat to the loss of our fertility might motivate people to pay more attention to their environmental health.