Chloroform, drinking water

Purification of drinking water by adding CI2 to kill bacteria is a source of electrophilic chlorine and contributes a nonenzymatic pathway for a chlorina tion and subsequent chloroform formation Al though some of the odor associated with tap water may be due to chloroform more of it probably results from chlorination of algae produced organic com pounds... 

Although simple analytical tests often provide the needed information regarding a water sample, such as the formation and presence of chloroform and other organohaUdes in drinking water, require some very speciali2ed methods of analysis. The separation of trace metals into total and uncomplexed species also requires special sample handling and analysis (12). 

Trihalomethanes. Wherever chlorine is used as a disinfectant in drinking-water treatment, trihalomethanes (THMs) generaUy are present in the finished water. The THMs usuaUy formed are trichloromethane (chloroform), bromodichloromethane, dibromochloromethane, and tribromomethane (bromoform). There are four main techniques for the analysis of THMs headspace, Hquid— Hquid extraction (Ue), adsorption—elution (purge—trap), and direct aqueous injection. The final step in each technique involves separation by gas—Hquid chromatography with a 2 mm ID coUed glass column containing 10 wt % squalene on chromosorb-W-AW (149—177 p.m (80—100 mesh)) with detection generaUy by electron capture. 

THMs are a byproduct of the chlorination process that most public drinking water systems use for disinfection. Chloroform is the primary THM of concern. EPA does not allow public systems to have more than 100 parts per billion (ppb) of THMs in their treated water. Some municipal systems have had difficulty in meeting this standard. 

Drinking water containing chloroform at maximmn allowable EPA limit 42... 

Jorgenson TA, Meierhenry EF, Rushbrook CJ, et al. 1985. Carcinogenicity of chloroform in drinking water to male Osbome-Mendel rats and female B6C3Fj mice. Fundam Appl Toxicol 5 760-769. 

Steup DR, Wiersma D, McMillan DA, et al. 1991. Pretreatment with drinking water solutions containing trichloroethylene or chloroform enhances the hepatotoxicity of carbon tetrachloride in Fischer 344 rats. Fund Appl Toxicol 16 798-809. 

Chlorine dioxide has been used widely in Europe since the early 1940 s as a drinking water disinfectant. More recently the USA has suggested the use of chlorine dioxide to reduce the formation of chloro-organic compounds particularly chloroform and other trihalomethanes (THM s) which are known carcinogens(7). 

Drinking water and various submixtures National Institute of of the full seven-chemical mixture as a Environmental Health promoter in the carcinogenic process Sciences (arsenic, benzene, chloroform, chromium, lead, trichloroethylene, and phenol) (rats)... 

We mentioned in Chapter 2 (Section 2.6.1) that a purge-and-trap procedure sometimes precedes an analysis by gas chromatography. An example of this procedure is found in the City of Lincoln, Nebraska, Water Treatment Plant Laboratory. Water treatment includes chlorination. When water is chlorinated, chlorine reacts with organic matter to form trihalomethanes (THMs), such as chloroform, bromoform, bromodichloromethane, and chlorod-ibromomethane. THMs in water are regulated by the Safe Drinking Water Act, and so the laboratory must analyze the treated water to determine their concentration. 

Note that some of the risk information is actuarial (based on statistical data, typically collected and organized by insurance companies), and some of it has been derived from the type of risk assessment discussed in this book (chloroform in chlorinated drinking water, afla-toxin in peanut products). While the uncertainties associated with the figures in Table 11.2 are much greater for some risks than for others (not a trivial problem in presentation of risk data), such a presentation, it would seem, is helpful to people who are trying to acquire some understanding of extremely low probability events, of the order of one-in-one million. 

You are probably exposed to small amounts of chloroform in your drinking water and in beverages (such as soft drinks) made using water that contains chloroform. You can also get chloroform in your body by eating food, by breathing air, and by skin contact with water that contains it. You are most likely to be exposed to chloroform by drinking water and breathing... 

Chloroform can enter your body if you breathe air, eat food, or drink water that contains chloroform. Chloroform easily enters your body through the skin. Therefore, chloroform may also enter your body if you take a bath or shower in water containing chloroform. In addition, you can breathe in chloroform if the shower water is hot enough for chloroform to evaporate. Studies in people and in animals show that after you breathe air or eat food that has chloroform in it, the chloroform can quickly enter your bloodstream from your lungs or intestines. Inside your body, chloroform is carried by the blood to all parts of your body, such as the fat, liver, and kidneys. Chloroform usually collects in body fat however, its volatility ensures that it will eventually be removed once the exposure has been removed. Some of the chloroform that enters your body leaves unchanged in the air that you breathe out, and some chloroform in your body is broken down into other chemicals. These chemicals are known as breakdown products or metabolites, and some of them can attach to other chemicals inside the cells of your body and may cause harmful effects if they collect in high enough amounts in your body. Some of the metabolites also leave the body in the air you breathe out. Only a small amount of the breakdown products leaves the body in the urine and stool. 

The EPA sets rules for the amount of chloroform allowed in water. The EPA limit for total trihalomethanes, a class of chemicals that includes chloroform, in drinking water is 100 micrograms per liter (pg/L, 1 pg/L = 1 ppb in water). Furthermore, EPA requires that spills of 10 pounds or more of chloroform into the environment be reported to the National Response Center. 

The effects of chronic oral exposure to chloroform, as a by-product of the chlorination of drinking water, were evaluated in four epidemiology studies (Alavanja et al. 1978 Cantor et al. 1978 Saurez-Varela et al. 1994 Young et al. 1981). The association between the incidence of gastrointestinal cancer in humans and the chlorination of drinking water is discussed in Section 2.2.2.8. The data from these studies should be viewed with caution as many other known or suspected carcinogens are known to exist in chlorinated drinking water. 

Pereira (1994) provided further evidence of the effect of dosing method (gavage versus drinking water) and vehicle (com oil versus water) on hepatic cell proliferation in female B6C3Fi mice. Animals received either 263 mg/kg/day chloroform by gavage in com oil or 1,800 ppm chloroform in drinking water,... 

Larson et al. (1994b) exposed female mice to 3, 10, 34, 90, 238, and 477 mg/kg/day of chloroform in com oil via gavage for 5 days a week for 3 weeks. Mice were also dosed with 16, 43, 82, 184, or 329 mg/kg/day of chloroform in the drinking water for 7 day a week for 3 weeks. In both studies, no increases in cell proliferation were noted and no significant changes in renal histopathology were reported. 

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