Semen quality, assessed in terms of sperm concentration and total sperm counts, continues to decline in Western countries (Levine et al., 2017). Fewer studies are available from non-Western countries, but recently, reports of alarming declines among healthy semen donors in China have appeared (Yuan et al. 2018).
The proportion of men with normal total motile sperm count, a measure highly relevant to fertilisation success, was found to have declined by approximately 10% between 2002 and 2017 in a population of men presenting to fertility centres in Spain and the USA (Tiegs et al. 2019). Similar observations were made among sperm donors (Chang et al. 2018).
The causes of these worrying developments are not fully elucidated but are likely to be complex. Lifestyle factors such as illicit drug use and maternal smoking during pregnancy play a role, as do poor nutrition, stress and genetic factors (Skakkebæk et al., 2022, Skakkebaek et al., 2016). It has been hypothesised that these problems are also linked to chemical exposures that originate from the use of fossil fuels in electricity generation, transport, petrochemistry, and most importantly plastic production (Skakkebaek et al., 2022).