[Drinking water chlorination and adverse health effects: review of epidemiological studies]

Toxicological aspects of trihalomethanes: a systematic review

Chlorine is considered the most used chemical agent for water disinfection worldwide. However, water chlorination can lead to by-product generation which can be toxic to humans. The present study aimed to perform a systematic review on the toxicity of trihalomethanes (THMs) through bioindicators of cytotoxicity, genotoxicity, and mutagenicity. The results showed that studies on the effects of THMs on DNA are a current research concern for evaluating the toxicity of the pure compounds and real samples involving several types including water for recreational use, reused water, and drinking water. THMs deleterious effects have been assessed using several biosystems, where the Ames test along with experimental animal models were the most cited. A wide range of THM concentrations have been tested. Nevertheless, DNA damage was demonstrated, highlighting the potential human health risk. Among the studied THMs, chloroform presented a different action mechanism when compared with brominated THMs, with the former being cytotoxic while brominated THMs (bromodichloromethane, bromoform, and dibromochloromethane) were cytotoxic, genotoxic, and mutagenic. The described evidence in this research highlights the relevance of this topic as a human health issue. Nevertheless, research aimed to represent THMs current exposure conditions in a more accurate way would be needed to understand the real impact on human health.

Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer

STUDY OBJECTIVE

To evaluate whether consumption of chlorinated drinking water is associated with bladder cancer.

DESIGN

A bibliographic search was conducted and the authors selected studies evaluating individual consumption of chlorinated drinking water and bladder cancer. The authors extracted from each study risk estimates for intermediate and long term (>40 years) consumption of chlorinated water, stratified by sex when possible, and performed meta-analysis for the two exposure levels. A meta-analysis was also performed of the dose-response regression slopes.

SETTING

Populations in Europe and North America.

PARTICIPANTS

Those included in six case-control studies (6084 incident bladder cancer cases, 10,816 controls) and two cohort studies (124 incident bladder cancer cases) fulfilling the inclusion criteria.

MAIN RESULTS

Ever consumption of chlorinated drinking water was associated with an increased risk of bladder cancer in men (combined OR=1.4, 95%CI 1.1 to 1.9) and women (combined OR=1.2, 95%CI 0.7 to 1.8). The combined OR for mid-term exposure in both genders was 1.1 (95% CI 1.0 to 1.2) and for long term exposure was 1.4 (95%CI 1.2 to 1.7). The combined estimate of the slope for a linear increase in risk was 1.13 (95% CI 1.08 to 1.20) for 20 years and 1.27 (95% CI 1.15 to 1.43) for 40 years of exposure in both sexes.

CONCLUSIONS

This meta-analysis of the best available epidemiological evidence indicates that long term consumption of chlorinated drinking water is associated with bladder cancer, particularly in men. The observed relative risk is only moderately high, but the population attributable risk could be important as the vast majority of the population of industrialised countries is potentially exposed to chlorination byproducts for long time periods.

[Halogenated by-products of chlorination in tap water]

OBJECTIVE

The presence of trihalomethanes in the water systems of several Spanish cities has been demonstrated. The aim of this study was to analyze trihalomethane concentrations in the water provided for human consumption in the city of Barcelona.

METHODS

We analyzed 151 water samples collected in 1998. The analyses were performed in the Public Health Laboratory of Barcelona using the purge-and-trap method and subsequent determination by gas chromatography and mass spectrometry. The results are presented according to the source of the water: the rivers of Llobregat or Ter, or a mixture of these.

RESULTS

Trihalomethane concentrations in the water from Ter were relatively low, with a predominance of chloroform and bromodichloromethane, while concentrations in the water from Llobregat were much higher, with a predominance of bromoform and dibromochloromethane. Mixed water showed intermediate concentrations. The total concentrations reached in the water from Llobregat were above 100 microg/l.

CONCLUSIONS

The results show the need to continue reducing organic pollution and halogenated compounds in the water used for human consumption in Barcelona.