Validating urinary trichloroacetic acid as a biomarker of exposure for disinfection by -products in drinking water

Disinfection by-products (DBPs) in drinking water represent a pervasive public health exposure issue and a difficult challenge for epidemiology. Validation of a biomarker of exposure is essential for progress in resolving causation aspects of this issue. Recent studies from our research group in Adelaide, South Australia and Edmonton, Alberta confirmed trichloroacetic acid (TCAA) to be the most promising candidate as a biomarker of exposure to DBPs. The objectives of this study were to validate urinary TCAA excretion as a biomarker of exposure to DBPs in a larger cohort, examine intraindividual and interindividual variability of TCAA excretion, and explore the feasibility of using TCAA as a biomarker in the field study. A total of 52 healthy women participated in the study. Participants consumed supplied tap water for 15 days and provided urine and blood samples for TCAA measurements. The findings revealed that (1) the utility of TCAA as a surrogate of other DBP compounds depended on the nature of water treatment systems and geographical locations; (2) background levels of TCAA in urine and blood were detected; (3) TCAA levels in blood and urine increased with increased amounts of TCAA ingested; (4) there was no correlation between dichloroacetic acid (DCAA) ingestion and excretion; (5) laboratory variation was not a major contributor to overall variation; (6) interindividual reliability was relatively high; (7) intraindividual variability contributed to background noise to a certain extent (ICC>0.70); (8) the correlations between measurements of TCAA concentration in water/amount of TCAA ingestion and urinary TCAA excretion were modestly high (r: 0.55--0.77, p<0.001); (9) the correlations between measurements of TCAA concentration in water/amount of TCAA ingestion and blood TCAA concentration were high (r: 0.77--0.82, p<0.001); (10) urinary TCAA measures or multiple days' urinary TCAA measures improved the prediction of TCAA ingestion through urinary TCAA excretion; (11) it is feasible to use TCAA as a biomarker of exposure in epidemiological studies and public health surveillance. In conclusion, TCAA can be a valid, reliable, and feasible biomarker of exposure for DBPs in drinking water.