In this issue of OEM, Iszatt and her colleagues present a study on water disinfection by-products (DBPs) and the associated risk of poor semen quality.1 They report no evidence of elevated risk in association with total trihalomethanes (THMs), chloroform or brominated THMs in public drinking water. They included a large sample of men who attended fertility clinics in areas with contrasted water quality in the UK, and used sophisticated modelling of THM levels in drinking water from routine measurements in distribution networks.

This study is an important addition in the field of investigations of reproductive risks of DBP exposure. The potential impact on male fertility has generated much less work than pregnancy outcomes although it has some relevance based on animal evidence;2 this is probably explained by the specific difficulties in measuring the outcome. Three previous studies …