Urinary excretion half life of trichloroacetic acid as a biomarker of exposure to chlorinated drinking water disinfection by-products: Figure 1

Abstract

Aims: To measure accurately urinary elimination half life of trichloroacetic acid (TCAA). Methods: A longitudinal pilot exposure/intervention study measured the elimination half life of TCAA in urine. Beverage consumption was limited to a public water supply and bottled water of known TCAA concentration, and ingestion volume was managed. The five participants limited fluid consumption to only the water provided. Consumption journals were kept by each participant and their daily first morning urine (FMU) samples were analysed for TCAA and creatinine. TCAA elimination half life curves were generated from a two week washout period using TCAA-free bottled water. Results: Individual elimination half lives ranged from 2.1 to 6.3 days, for single compartment exponential decay, the model which fit the data. Conclusion: Urinary TCAA is persistent enough to be viable as a biomarker of medium term (days) exposure to drinking water TCAA ingestion within a range of realistic concentrations.C hlorinated disinfection by-products (DBPs) in drinking water pose a challenge to the epidemiological study of both cancer and adverse reproductive outcomes. 1 Reviews of evidence on adverse reproductive outcomes have consistently cited a major need to improve individual exposure assessment. 1-3 Biomarkers have been suggested as the potential ''gold standard'' for achieving this improvement, 3 and their development and validation has been recommended. 1 Of the many DBPs that are present in chlorinated waters, the trihalomethanes (THMs) and haloacetic acids (HAAs) are the major DBPs. Consequently, these classes of DBPs have received the most attention as potential biomarkers of exposure for DBPs. Initial work by Weisel and co-workers 4 and limited pharmacokinetic literature 5 6 showed promise for trichloroacetic acid (TCAA) for integrating medium term exposure to drinking water DBPs. We previously performed a longitudinal pilot study to measure the urinary elimination half life of TCAA. 7 Limitations in that study design indicated the need for a better controlled study to provide greater confidence in the human TCAA elimination kinetics. METHODS Volunteer recruitmentVolunteers from Edmonton, herein referred to as City A, were sought for participation in the study. Five volunteers in total, three males (ages 27, 37, 52) and two females (ages 28, 29), were recruited. All of the volunteers were either students or staff from our research group. The Health Ethics Research Board of the University of Alberta approved the study protocol, and we obtained informed written consent from participants at enrolment in the trial. Study designDrinking water in City A had very low levels of TCAA (5-20 mg/l); therefore, water was imported from another city (referred to as City B) with higher TCAA (50-180 mg/l).This study was designed to measure the half life of urinary elimination for TCAA. Participants consumed normal tap water from City B for two weeks and then switched to TCAAfree bottled water for two weeks. Bottled water was obtained from the Sierra Spr...

Validation of urinary trichloroacetic acid as a biomarker of exposure to drinking water disinfection by-products

“…More recently, Froese et al (2002) and Bader et al (2004) studied exposure to TCAA via drinking tap water. Ten volunteers ingested TCAA-containing tap water for 12 d at concentrations ranging from 1.8 to 29 mg/L, and the estimated urinary elimination half-lives ranged from 2.3 to 2.9 d .…”

“…Ten volunteers ingested TCAA-containing tap water for 12 d at concentrations ranging from 1.8 to 29 mg/L, and the estimated urinary elimination half-lives ranged from 2.3 to 2.9 d . The estimated urinary elimination half-lives varied from 2.1 to 6.3 d in five volunteers who consumed TCAA-containing tap water (50 -180 mg/L) for 2 weeks (Bader et al 2004). …”

Overview of Disinfection By-products and Associated Health Effects

“…However, these biomarkers are of limited use for evaluating risks associated with cancer, reproductive outcomes, and other health effects that require longer exposure periods. Urine trichloroacetic acid has been proposed as a valid biomarker of ingested DBPs, as its halflife is longer than consecutive exposure events, reaching steady levels that correlate with levels ingested through drinking water [44]. However, the validity of this method is limited, given that trichloroacetic acid is a metabolite of other substances, and only the ingestion pathway is covered (haloacetic acids are not volatile or skin-permeable) [45].…”

Green Chemistry in Urinalysis for Trichloroethanol and Trichloroacetic Acid as Markers of Exposure to Chlorinated Hydrocarbon Solvents

“…The sensitivity is apparently insufficient, however, for monitoring TCA levels in urine of general populations who are exposed to dis-infection byproducts in chlorination-treated drinking water [41][42][43][44][45] . Monitoring the expected TCA levels of 0.5 to 25 µg/l urine needs much more sophisticated expensive methods such as isotope-dilution HPLC-tandem mass spectrometry 43,44) .…”