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

Abstract

The question of whether disinfection byproducts (DPBs) in drinking water pose any health risk to humans has been an ongoing issue since the discovery of DPBs in 1974. Although toxicology experiments with individual DPBs are necessary to establish plausible mechanisms of toxic action, epidemiologic studies of human populations are necessary to establish whether actual DPB exposures from drinking water pose a human health risk. Such studies have historically been focused on cancer outcomes, but more recently a number of studies have addressed the possibility of adverse reproductive outcomes (1-12).The ability of epidemiologic studies to address these health questions has been seriously limited by inadequate individual assessment of exposure to DPBs (13,14). A major prospect for improved exposure assessment for epidemiologic studies of adverse reproductive outcomes is to validate a biomarker of exposure to DPBs. Desirable characteristics of potential biomarkers of DPB exposure have been discussed by Froese et al. (15).To date, the only DPBs evaluated for use as biomarkers of exposure have been the trihalomethanes (THMs) and the haloacetic acids (HAAs). Weisel et al. (16) found that most background breath samples from a cohort of women who had participated in the Klotz and Pyrch (8) study were nondetectable for THMs in exhaled breath. Measurable levels of THMs were obtained in post-shower breath samples, and these breath values correlated with water levels of THMs. However, breath levels of THMs as a biomarker of exposure to DPBs do not persist for sufficient time to integrate exposure measurement over more than minutes to hours, at most. Likewise, measurable THM exposures are limited to inhalation and dermal exposure from showering or bathing. THM levels in breath will not reflect ingestion exposure because of rapid first-pass metabolism of ingested THMs in the liver. THMs in blood were demonstrated to be feasible for evaluating background THM exposure (17), but blood sampling is an invasive procedure.The potential of two HAAs, dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), as DPB biomarkers in urine was examined with a cross-sectional study of a cohort of 49 women, who provided 42 valid samples (16,18). That study found that DCAA was rapidly metabolized and that urine levels showed no difference between low-exposure and high-exposure groups. However, TCAA did show higher excretion levels for higher-TCAA-exposure versus lower-TCAAexposure groups. TCAA excretion in urine did not correlate significantly with measured water concentrations of TCAA. A more detailed TCAA exposure calculation was done by accounting for the volume of water consumed, the proportion of heated water used (estimating a 39% reduction in TCAA from boiling), and the use of home water filters (estimating a 70% reduction for any filter type). With these adjustments, a significant correlation (R of 0.73, n = 42) was found between estimated TCAA ingestion (estimated as micrograms of TCAA consumed in the previous 48 hr) and measured TCAA...

The relationship between water concentrations and individual uptake of chloroform: a simulation study.

“…For other nonvolatile DBPs, for which ingestion is the main route of uptake, the correlation between water concentration and overall uptake may be much better than for chloroform, which has multiple routes and pathways. However, two studies found no relation between nonvolatile trichloroacetic acid (TCAA) concentrations measured in urine and TCAA concentrations in home tap water, although personal consumption information combined with the TCAA concentration in tap water was found to be correlated with the TCAA urine concentrations (Weisel et al 1999;Froese et al 2002).…”

Peer Reviewed: Disinfection Byproducts: The Next Generation

“…The speciation differences found in tap water were mirrored in the women's blood samples. DBPs have also been measured in the exhaled breath of people exposed to DBPs through drinking, showering, and bathing (10,14,15), in the blood and exhaled breath of swimmers (33)(34)(35), and in the urine of individuals exposed to HAAs through drinking water (13). Researchers at NCI, CDC, and EPA are planning a collaborative human exposure study to identify previously undetected markers of exposure to nonvolatile DBPs and their metabolites in urine.…”

Urinary levels of trichloroacetic acid, a disinfection by-product in chlorinated drinking water, in a human reference population.

“…Urinary TCAA has been proposed as a biomarker of chronic ingestion exposure to HAAs from chlorinated drinking water (Bader et al 2001;Froese et al 2002;Kim et al 1999;Weisel et al 1999). In addition, the levels of TCAA in urine (Bloemen et al 2001;Fisher et al 1998;Raaschou-Nielsen et al 2001;Vartiainen et al 1993) and in plasma (Ziglio 1981) have been used as a biomarker for occupational or unintentional exposure to trichloroethylene, (TCE), a compound that is partially metabolized to TCAA in humans.…”