Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Adverse Reproductive Outcomes and Disinfection Byproduct Exposure
In North West England, drinking water is supplied to 7 million people by the water company United Utilities. The company introduced enhanced coagulation for some of their treatment works during 2003 and 2004. Compared to conventional coagulation, enhanced coagulation improves removal of disinfection byproduct (DBP) precursors and should therefore reduce DBP formation potential. This intervention provided a unique opportunity to study potential effects of DBPs, in particular trihalomethanes (THMs), on birth outcomes, particularly since potential confounders (eg, socioeconomic factors) did not change over the short period. Areas where no treatment changes occurred acted as a control. Our aim was to compare rates of stillbirth and low birth weight 3 years prior (2000–2002) to treatment changes occurring with rates 3 years after (2005–2007) the changes took place.
We linked information on THMs and enhanced coagulation status of water supply zones to births and stillbirths from the national birth register, using the point-in-polygon method in geographical information systems, with the third trimester as the critical exposure period. Differences in small-area rates of stillbirth and low birth weight before and after treatment changes were modelled against change in mean annual total THM (TTHM) concentrations using Poisson regression. Additionally, areas were categorized into low, medium, and high change in TTHM concentrations and the changes in rates of stillbirth and low birth weight were estimated in each category using Poisson regression. Models were adjusted for potential confounders such as maternal age and social deprivation (Carstairs' deprivation score).
Enhanced coagulation reduced TTHM levels. Preliminary results suggest an association between reduction of stillbirth rates and change to enhanced coagulation, possibly mediated by reduction in TTHM. However, we found little association between reduction of low birth weight rates and change to enhanced coagulation.
Our preliminary findings are inconclusive. Further, analyses will investigate the individual THMs, bromodichloromethane, bromodichloromethane, bromoform, and chloroform.