Sources of Variability in Levels and Exposure to Trihalomethanes

Abstract

TAA2-O-06 Introduction: As a preliminary to a cohort study to evaluate the increased risk of reproductive effects associated with trihalomethane (THM) exposure during pregnancy, we 1) evaluated potential sources of variability in household THM levels; 2) examined the validity of regulatory THM measurements as a tool to monitor THM levels in households; 3) evaluated the influence of personal water-related habits in the estimation of exposure to THM through ingestion, inhalation, and dermal absorption, and 4) explored THM levels in swimming pools as a source of THM exposure. Methods: We sampled 109 women from an ongoing cohort of pregnant women in Brittany (France). They were visited at home for an interview and collection of tap water between October and December 2004. Forty-three of them were visited again in April to May 2005. We collected individual information on source and amount of drinking water, frequency of showering, bathing, swimming pool attendance, and household characteristics. We obtained 309 THM measurements: 152 specifically for the study and 157 from regulatory agencies. Personal information and environmental data were combined to calculate ingestion, showering, bathing, and swimming pool THM exposure indices. We combined those exposure situations to create a combined total THM exposure index. Results: Average THM levels from our measurements in October, November to December, and April to May were 61.3, 45.1, and 54.5 μg/L, respectively. Geographic variability was low and characteristics of the household did not influence THM levels. Average water consumption during pregnancy was 2 L/day. Water source in the household was bottled for 90%, municipal for 8%, and other sources for 2%. Forty-seven percent of the study population attended swimming pools during pregnancy. The geometric mean of total THM uptake including drinking water, showering, bathing, and swimming-pool attendance 1.19 μg/day. Showering contributed 68% to the total THM exposure, swimming in pools 17%, bathing 14%, and drinking water 1%. Average THM levels from the regional (59.9 μg/L) and local (42.7 μg/L) regulatory agencies were slightly different to our measurements (53.4 μg/L), adjusting for month, year, and distribution system. Discussion and Conclusions: In a setting with low geographic variability, individual data are more relevant than environmental levels to determine personal THM exposure. Individual exposure to THMs was dominated by inhalation and dermal absorption while showering, bathing, and swimming pool attendance, since our study population mainly drank bottled water.