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Water Disinfectants & disinfectant by-products

3. How can disinfectants and their by-products affect health?

  • 3.1 Disinfectants toxicology
  • 3.2 Chlorine by-products toxicology
  • 3.3 Chlorine dioxide by-products toxicology
  • 3.4 Ozonation by-products toxicology

3.1 Disinfectants toxicology

Disinfectants themselves, at the concentrations used, do not appear to contribute to toxicity but it is the by-products and breakdown products that have received attention. Chlorine gas, chloramine and chlorine dioxide are strong respiratory irritants, but only at much higher exposure than would result from the release of vapors through from drinking-water. More...

3.2 Chlorine by-products toxicology

The different groups of chlorine by-products have different toxicity. They can particularly affect the liver and kidney of laboratory rats and mice:

  • The toxicity of the trihalomethanes (THMs) in laboratory animals is higher when administered with corn oil than with water. Chloroform is not considered to be genotoxic and induces cancers only at high doses after tissues have been damaged. The other THMs appear to be weakly genotoxic. At high doses, some induce tumours of the liver and kidney and others of the large intestine, when administered in corn oil.
  • The haloacetic acids (HAAs) produce a range of effects in rodents including tumours of the liver and reproductive and neurological effects, but only at very high doses. They are only weakly genotoxic but this does not appear to be how they cause tumours.
  • Chloral hydrate has been shown to potentially induce liver tumours and other health effects in laboratory rodents but only at very high doses. Some of the other halogenated aldehydes and ketones are highly genotoxic possibly carcinogenic and one, chloroacetaldehyde has induced liver tumours in laboratory animals.
  • The haloacetonitriles have not been well studied. Some are mutagenic, but may not induce tumours.
  • MX is a very potent mutagen in bacteria and also appears to cause some tumours in laboratory rats.


3.3 Chlorine dioxide by-products toxicology

The by-products of chlorine dioxide, chlorite and chlorate, can damage red blood cells. Chlorite may cause mild neurobehavioural effects in rat pups at relatively high doses but does not increase tumours in laboratory animals. Chlorate shows lower toxicity than chlorite. More...

3.4 Ozonation by-products toxicology

Bromate, the main by-product of ozonation, has been shown to induce tumours of the kidney, peritoneum and thyroid in rodents at high doses. More...

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