VALIDATING URINARY TRICHLOROACETIC ACID AS A BIOMARKER OF EXPOSURE FOR DISINFECTION BY-PRODUCTS IN DRINKING WATER

Abstract

ISEE-114 Introduction: Epidemiologic evidence of disinfection by-products (DBPs) causing adverse human health effects needs improved assessment of individual drinking water exposure to DBPs. Development of a feasible biomarker offers an approach to this need. Trichloroacetic acid (TCAA) in urine was confirmed to have sufficiently long retention (urinary excretion half lives from 2 to s6 days) in two previous human exposure pilot trials (ten participants in Adelaide, Australia and five participants in Edmonton, Canada) to make urinary TCAA a promising candidate as a biomarker. Aim: The current study was to validate urinary TCAA as a biomarker of non-volatile DBP exposure via drinking water. Methods: Between May 2003 and April 2004, fifty-two healthy women of reproductive age were recruited to participate in this study. Following an initial telephone interview, eligible volunteers were selected to obtain demographic data, patterns of food, beverage and water consumption, and to set up schedules for water delivery and blood and urine sample collections. All participants were randomly stratified into five sub-groups. Each exposure level was assigned a different exposure status. Each participant ingested supplied municipal tap water, diluted to a known degree with TCAA-free water, every day for a 15-day period of time, and provided urine samples on the 1st, 2nd, 8th, 13th, 14th, 15th, and 16th day of the exposure period. Some provided blood samples on the 1st, 8th, 14th, and 15th day. Results: The means of background TCAA levels were 6.6 mg/l for urinary TCAA concentration, 5.2 mg/g cr for creatinine-adjusted TCAA, 6.1 mg/d for amount of urinary TCAA excretion, and 13 mg/l for blood TCAA concentration. There were good correlations between urinary TCAA excretion and TCAA ingestion (R values: 0.72 – 0.80) and between blood TCAA concentration and TCAA ingestion (R = 0.74). Variation in volume of tap water intake affected the amount of TCAA intake in the majority of individuals. The correction of urinary excretion to urinary creatinine improved the result of intra-individual variability to a limited extent. On average, 37% of amount of ingested TCAA was measured in urine samples. The intra-individual variability of urinary TCAA excretion was relatively small after Exposure Day 7 (intra-class correlation coefficient >0.90). Discussion: The value of TCAA as a biomarker of exposure for DBPs in drinking water will be characterized.