As many as one in five healthy men aged 18 to 25 produces abnormally low levels of sperm, and often the sperm he does produce is of poor quality, either structurally defective or functionally poor.
There are many possible explanations for this, ranging from chemicals in the environment to tight underwear, but none on its own has been strong enough to explain the trend.
The latest study suggests a direct effect on the sperm’s agility and its ability to penetrate the human egg cell.
About a third of the nearly 100 industrial chemicals tested affected the “catsper” protein that is vital for sperm function, the study found. Interestingly, the study did not find that bisphenol-A, used in plastics and mentioned in other studies, had any effect on the catsper protein.
But Timo Strünker, one of the lead authors of the study, cautioned: “The fact that BPS does not directly interfere with human sperm function does not mean that BPA does not interfere with other steps that are required for fertilisation.”