Trichloroacetic acid as a biomarker of exposure to disinfection by-products in drinking water: A human exposure trial in Adelaide, Australia

We addressed the need for a biomarker of ingestion exposure to drinking water disinfection by-products by performing a human exposure trial. We evaluated urinary excretion of trichloroacetic acid (TCAA) as an exposure biomarker using 10 volunteers who normally consume their domestic tap water. We recruited the volunteers at a water quality research laboratory in Adelaide, Australia. Participants maintained a detailed consumption and exposure diary over the 5-week study. We also analyzed tap water and first morning urine (FMU) samples for TCAA, and tap water for chloral hydrate (CH). We documented both interindividual and intra-individual variability in TCAA ingestion and urinary excretion, and both were substantial. With a TCAA-free bottled water intervention, we used creatinine-adjusted urinary TCAA levels to estimate urinary TCAA excretion half-lives for three of the participants. We observed correspondence over time between estimated TCAA excretion, calculated from TCAA + CH ingestion levels, and measured TCAA urinary excretion. This study demonstrates the merits and feasibility of using TCAA in FMU as an exposure biomarker, and reveals remaining concerns about possible alternate sources of TCAA exposure for individuals with low drinking water ingestion exposure.