Carcinogenic chlorinated compounds

Ozone can be used to replace chlorine for the sterilization of water. Replacement of chlorine is desirable because chlorination increases the salinity of water. The more salt in the water the less value it has for later use in, for example, irrigation of cropland. When used to sterilize water, chlorine reacts with trace organic compounds to form carcinogenic chlorine compounds such as chloroform. The use of ozone to replace chlorine in water treatment will eliminate chlorination-induced salinity and carcinogenic chlorinated organic compounds. Because of its instability, any residual ozone not consumed in purifying the water rapidly decomposes to ordinary oxygen. 

In more recent years, efforts have been stepped up to control environmental pollution, with the result that in many areas residues of such compounds in fish and shellfish are decreasing substantially from previous levels. The chlorinated compounds mentioned earlier have the ability at sustained high doses in rodents to promote the development of liver cancer thus, they have been called "carcinogenic." When viewed in terms of projected hazards to human health, however, human exposure is usually low level and sporadic. Most of the detectable levels of chlorinated compounds in various fish and shellfish pose no hazard to human health. 

Chlorinated organic compounds present in water, due to their carcinogenic nature, have become a great concern with respect to human health. Such substances are formed when humic acids react with chlorine in disinfection processes. Ozonation alone is generally not suited for the complete oxidation of chlorinated compounds because scavenger compounds such as acetic acid, formic acid, and oxalic acid can form and accumulate as by-products in the... 

DOT CLASSIFICATION 6.1 Label KEEP AWAY FROM FOOD SAFETY PROFILE Suspected carcinogen with experimental carcinogenic and mmorigenic data. Poison by intraperitoneal route. Moderately toxic by ingestion. Experimental teratogenic effects. Human mutation data reported. A skin and eye irritant. Combustible when exposed to heat or flame. When heated to decomposition or on contact with acid or acid fumes, it emits highly toxic fumes of aniline and chlorine compounds. Reacts explosively with aniline... 

In spite of all the efforts taken to purify public water supplies, many consumers are concerned about the quahty of the water that comes out of the taps in their homes, schools, and places of business. Parents of small children are especially worried about chemicals such as lead and carcinogenic organic compounds that are chlorine disinfection by-products. Many have turned to bottled water or home water treatment devices. 

Many landfills contain VOCs (volatile organic chemicals). This group of chemicals includes benzene and toluene (both carcinogens), chlorinated hydrocarbons, such as carbon tetrachloride, and trichloroethylene, which previously was used as a dry-cleaning solvent. Even though these compounds are not very soluble in water, they do accumulate at the parts-per-million level. Their long-term effect on human health is unknown at this time. 

Because some of these chlorinated compounds are suspected carcinogens, adequate ventilation is essential when they are used as solvents. 

Data on the occurrence of low molecular weight chlorinated compounds have until recently been very sparse but the impact of 2 issues, namely the effect of fluorocarbons on the ozone layer, and the suspicion that the trihalomethanes found in chlorinated waters, and some solvents, are carcinogenic, has led to a rapid increase in reported analysis in air, and in surface and drinking water. 

The toxicity of chlorine residuals to aquatic life has been well documented. Studies indicate that at chlorine concentrations in excess of 0.01 mg/1, serious hazard to marine and estuarine life exists. This has led to the dechlorination of wastewaters before they are discharged into surface water bodies. In addition to being toxic to aquatic life, residuals of chlorine can produce halogenated organic compounds that are potentially toxic to man. Trihalomelhanes (chloroform and bromoform), which are carcinogens, are produced by chlorination. 

Liver cancer can also be a consequence of exposure to hepatotoxic chemicals. Natural hepatocarcinogens include fungal aflatoxins. Synthetic hepato-carcinogens include nitrosoamines, certain chlorinated hydrocarbons, polychlorinated biphenyls (PCBs), chloroform, carbon tetrachloride, dimethyl-benzanthracene, and vinyl chloride.Table 5.15 lists the chemical compounds that induce liver cancer or cirrhosis in experimental animals or... 

Evidence that many of these compounds can have adverse effects on the immune, endocrine and nervous systems and that some are carcinogenic has grown during the last decade. The role of chlorofluorocarbons (CFCs) and of methyl bromide in the ozone layer depletion is well established (ref. 3).It is therefore not surprising that many halogenated derivatives are cast as environmental and health villains by various concerned groups who call for total phase out of chlorine and chlorinated hydrocarbons. 

Klaunig JE, Ruch RJ, Pereira MA. 1986. Carcinogenicity of chlorinated methane and ethane compounds administered in drinking water to mice. Environ Health Perspect 69 89-95. 

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). 

Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

Potential hazards to humans may be connected with the use of chlorine-based washing systems. Apart from the direct occupational hazard, there are increasing concerns about the formation of potentially harmful by-products. Chlorine may react with organic compounds on the products and form hazardous organochlorines that are considered to be potential carcinogens (Beuchat, 1998 Betts and Everis, 2005). Betts and Everis (2005) suggest that a ban on the use of hypochlorite systems is likely in the future. 

The use of chlorine for disinfecting wastewaters or drinking water has become widespread in this century. Recently, however, the increasing presence and variety of aquatic contaminants has raised the question of the chemical fate of these contaminants when subjected to aqueous chlorination [36]. In fact, the production of organochlorine compounds in chlorinated water, including mutagenic and carcinogenic substances, is well established [37,38], A number of alternatives to chlorination are used in many parts of the world, but the risks associated with their by-products are even less well established [39],... 

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