Tag Archives: trihalomethanes (THMs)

Assessing exposure, reducing risk to trihalomethanes in drinking water

Chowdhury S. Exposure assessment for trihalomethanes in municipal drinking water and risk reduction strategy. Science of the Total Environment. 2013 Jul 18;463-464C:922-930. doi: 10.1016/j.scitotenv.2013.06.104.

Lifetime exposure to disinfection byproducts (DBPs) in municipal water may pose risks to human health. Current approaches of exposure assessments use DBPs in cold water during showering, while warming of chlorinated water during showering may increase trihalomethane (THM) formation in the presence of free residual chlorine. Further, DBP exposure through dermal contact during showering is estimated using steady-state condition between the DBPs in shower water impacting on human skin and skin exposed to shower water. The lag times to achieve steady-state condition between DBPs in shower water and human skin can vary in the range of 9.8-391.2min, while shower duration is often less than the lag times. Assessment of exposure without incorporating these factors might have misinterpreted DBP exposure in some previous studies. In this study, exposure to THMs through ingestion was estimated using cold water THMs, while THM exposure through inhalation and dermal contact during showering was estimated using THMs in warm water. Inhalation of THMs was estimated using THM partition into the shower air, while dermal uptake was estimated by incorporating lag times (e.g., unsteady and steady-state phases of exposure) during showering. Probabilistic approach was followed to incorporate uncertainty in the assessment. Inhalation and dermal contact during showering contributed 25-60% of total exposure. Exposure to THMs during showering can be controlled by varying shower stall volume, shower duration and air exchange rate following power law equations. The findings might be useful in understanding exposure to THMs, which can be extended to other volatile compounds in municipal water.

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Risk of congenital anomalies from trihalomethane exposure during pregnancy

Grazuleviciene R, Kapustinskiene V, Vencloviene J, Buinauskiene J, Nieuwenhuijsen MJ. Risk of congenital anomalies in relation to the uptake of trihalomethane from drinking water during pregnancy. Occup Environ Med. 2013 Feb 12.

OBJECTIVES: Congenital anomalies have been inconsistently associated with maternal crude estimated exposure to drinking water trihalomethane (THM). We investigated the relationship between individual THM uptake during the first trimester of pregnancy and congenital anomalies.

METHODS: We estimated maternal THM uptake for 3074 live births using residential tap water concentrations, drinking water ingestion, showering and bathing, and uptake factors of THM in the blood. Multiple logistic regression was used to investigate the association of THM exposure with congenital anomalies.

RESULTS: We observed no statistically significant relationships between congenital anomalies and the total THM internal dose. We found little indication of a dose-response relationship for brominated THM and congenital heart anomalies. The relationship was statistically significant for bromodichloromethane (BDCM) (OR=2.16, 95% CI 1.05 to 4.46, highest vs lowest tertile) during the first month of pregnancy. During the first trimester of pregnancy, the probability of developing heart anomalies increased for every 0.1 μg/d increase in the BDCM and for every 0.01 μg/d increase in the internal dibromochloromethane (DBCM) dose (OR 1.70, 95% CI 1.09 to 2.66, and OR 1.25, 95% CI 1.01 to 1.54, respectively). A dose-response relationship was evident for musculoskeletal anomalies and DBCM exposure during the first and second months of pregnancy, while BDCM exposure tended to increase the risk of urogenital anomalies.

CONCLUSIONS: This study shows some evidence for an association between the internal dose of THM and the risk of congenital anomalies. In particular, increased prenatal exposure to brominated THM might increase the risk of congenital heart and musculoskeletal anomalies.

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Taiwan study found no association between THMs and kidney cancer

The Odds Ratio reported in this study is not significant, regardless of the interaction of hardness. If hardness did play a role, would it be calcium, or magnesium, or both? An interesting hypothesis, but just conjecture….

Liao, YH, Chen, CC, Chang, CC, Peng, CY, Chiu, HF, Wu, TN, and CY Yang. Trihalomethanes in drinking water and the risk of death from kidney cancer: does hardness in drinking water matter? J Toxicol Environ Health A. 2012 Mar 15;75(6):340-50.

Abstract: The objectives of this study were to (1) examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of development of kidney cancer and (2) determine whether hardness levels in drinking water modify the effects of TTHM on risk of kidney cancer induction. A matched case-control study was used to investigate the relationship between the risk of death attributed to kidney cancer and exposure to TTHM in drinking water in 53 municipalities in Taiwan. All kidney cancer deaths in the 53 municipalities from 1998 through 2007 were obtained. Controls were deaths from other causes and were pair-matched to the cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on TTHM levels and levels of hardness in drinking water were also collected. The municipality of residence for cancer cases and controls was presumed to be the source of the subject’s TTHM and hardness exposure via drinking water. Relative to individuals whose TTHM exposure level was <4.9 ppb, the adjusted OR (95% CI) for kidney cancer was 0.98 (0.77-1.25) for individuals who resided in municipalities served by drinking water with a TTHM exposure ≥4.9 ppb. However, evidence of an interaction was noted between the use of soft water and drinking water TTHM concentrations. Increased knowledge of the interaction between hardness and TTHM levels in reducing risk of kidney cancer development will aid in public policy decision and establishing standards to prevent disease occurrence.

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Summerhayes et al. 2012: Exposure to Trihalomethanes in Drinking Water and Small-for-gestational age Births

The abstract below appears to exagerate the findings of this study…..a Relative Risk (RR) of 1.06 does not even rise to the level of being called a “weak” association…..

Summerhayes, R.J., G.G. Morgan, H.P. Edwards, D. Lincoln, A. Earnest, B. Rahman, and J.R. Beard. 2012. Exposure to Trihalomethanes in Drinking Water and Small-for-gestational-age Births. Epidemiology. 2012 Jan;(1):15-22.

BACKGROUND: Trihalomethanes in drinking water have been associated with higher occurrence of small-for-gestational-age (SGA) births, although results have been inconsistent.

METHOD: We geocoded residential address for mother of live, singleton, term births to 33 water distribution systems in a large metropolitan area of New South Wales, Australia (314,982 births between 1998 and 2004) and classified births into <10th percentile and ≥10 percentile of weight for gestational age. Mean trihalomethane exposure was estimated by trimester and for the entire pregnancy based on monthly sampling in each of the 33 water distribution systems. We estimated the relative risk (RR) of SGA for exposure to trihalomethanes using log-binomial regression adjusting for confounding.

RESULTS: SGA births increased with mother’s third-trimester exposure to chloroform (RR=1.04 [95% confidence interval=1.02-1.06], across an interquartile range [IQR]=25 μg/L) and bromodichloromethane (1.02 [1.01-1.04], 5 μg/L). Larger associations were found for SGA less than third percentile. Smoking modified the effects of trihalomethane exposure, with generally larger associations in births to nonsmoking mother and weaker or protective associations in births to smoking mothers.

CONCLUSIONS: Mothers’ exposures during pregnancy to total trihalomethane as well as to chloroform and bromodichloromethane were associated with SGA. These associations were modified by maternal smoking during pregnancy.

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