Trihalomethanes and Semen Quality in England and Wales

Abstract

ISEE-0663 Background and Objective: Disinfection by-products (DBPs) have been associated with adverse semen outcomes in laboratory animals. Of the DBPs, there is stronger evidence for the bromo- and chloro-acetic acids, while that for trihalomethanes (THMs) is heterogenous. However, two small epidemiological studies have found no association between DBPs and adverse semen outcomes in humans. In a large case-control study, we investigated the association between individual and total trihalomethanes (TTHM) and low motile sperm concentration (MSC) in six water regions in England and Wales between 1999 and 2002. Methods: Men were recruited from 13 fertility clinics in 9 centres across England and Wales between 1999 and 2002. THM concentrations in water zones were linked to data on semen quality for 647 cases and 936 controls, based on the men’s residence at the time the semen sample was obtained. Low MSC was calculated relative to time since last ejaculation. TTHM levels were categorized as low (< 35.71 μg/l), medium (35.71–49.86 μg/l), or high (49.87–95 μg/l). Results: Preliminary analyses using a crude measure of THM exposure (annual average THM) found no increased risk associated with TTHM. There were some excess risks found with the individual THMs. Conclusion: Our preliminary findings are inconclusive. Further analyses will use quarterly THM exposure data weighted to the time of sampling for more precise exposure, and adjust for potential confounders.