Urinary Levels of Trichloroacetic Acid, a Disinfection By-Product in Chlorinated Drinking Water, in a Human Reference Population. (Research)

Article excerpt

Trichloroacetic acid (TCAA), a known mouse liver carcinogen and a possible human carcinogen, is found in chlorinated drinking water. We measured TCAA in archived urine samples from a reference population of 402 adults using isotope-dilution high-performance liquid chromatography-tandem mass spectrometry. TCAA was detected in 76% of the samples examined at concentrations ranging from < 0.5 [micro]g TCAA/L to more than 25 [micro]g/L; the 90th percentile concentration was 23 [micro]g/L (22 [micro]g TCAA/g creatinine); and the geometric mean and median concentrations were 2.9 [micro]g/L (2.6 [micro]g/g creatinine) and 3.3 [micro]g/L (3.2 [micro]g/g creatinine), respectively. The frequency of detection of TCAA in urban areas was higher than in rural areas (p = 0.00007), and sex and place of residence (i.e., urban vs. rural) were found to have a significant interaction in modulating the levels of TCAA (p = 0.012). Urban residents had higher mean levels of TCAA (men, 5.3 [micro]g/L, 3.8 [micro]g/g creatinine; women, 2.9 [micro]g/L, 2.8 [micro]g/g creatinine) than did rural residents (men, 2.2 [micro]g/L, 1.7 [micro]g/g creatinine; women, 2.6 [micro]g/L, 2.7 [micro]g/g creatinine). The higher frequency of detection of TCAA in urban than in rural areas and higher levels of TCAA among urban than among rural residents may reflect the fact that urban residents use primarily chlorinated water from public water supplies, whereas those in rural areas are more likely to obtain water from private wells, which typically are not chlorinated. Key words: exposure, human, trichloroacetic acid, urine. Environ Health Perspect 111:151-154 (2003). [Online 28 October 2002]

doi:10.1289/ehp.5644 available via http://dx.doi.org/

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The chemical disinfection of drinking water to control microbial contaminants has been one of the most successful public health measures ever undertaken. However, in the 1970s, the chemical disinfection of drinking water was discovered to produce disinfection byproducts (DBPs) (Rook 1974). Toxicologic studies on laboratory animals have found that some DBPs are carcinogenic and may have adverse reproductive outcomes (Boorman et al. 1999; Bull et al. 1995). When chlorine is used as the disinfecting agent, the volatile trihalomethanes (THMs) and the nonvolatile haloacetic acids (HAAs) are the most abundant groups of DBPs formed (Richardson 1998). Trichloroacetic acid (TCAA), one of the two major HAAs in water, is a mouse liver carcinogen; the U.S. Environmental Protection Agency (U.S. EPA) has classified TCAA as a possible human carcinogen (U.S. EPA 2001) and introduced regulations for the maximum contaminant levels of TCAA, among other DBPs, in drinking water.

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.

No clear association has been established between human exposure to HAAs in drinking water and adverse health effects. However, further studies to investigate the human health relevance of exposure to HAAs are warranted because of their potential harmful effects on human health. We report here the levels of TCAA in urine from a reference sample of the noninstitutionalized U.S. adult population using a rapid and selective technique (Kuklenyik et al. 2002) as a tool for assessing the internal dose of HAAs.

Materials and Methods

The urine samples analyzed for this study were selected from a nonrepresentative callback cohort of those collected during the Third National Health and Nutrition Examination Survey (NHANES III), which was conducted from 1988 through 1994 (NCHS 1994). …