What are trihalomethanes?

     Τrihalomethanes, or THMs, form when chlorine or other disinfectants that are used to control microbial contaminants in water react with organic matter in water. There are four types: trichloromethane or chloroform (CHCl3), dibromochloromethane (CHClBr2), bromodichloromethane (CHCl2Br), and tribromomethane or bromoform (CHBr3). Trihalomethanes are found in tap water and in the air of buildings where running water releases it into the air. However, trihalomethanes in the air have little effect on us.

Risks and health issues

      Trihalomethanes have been linked to an increased risk of cancer, and so they are considered carcinogens. They have also been linked to damage in the heart, lung, kidney, liver and central nervous system. A study showed that they may also lead to miscarriage: women who drank 5 or more glasses of water containing a high level of trihalomethanes had a miscarriage rate of 15.7%, while women who drank water containing lower levels of trihalomethanes had a miscarriage rate of 9.5%. Because of this, pregnant women are a high risk group.

      Increased health risks may not only be a result of the water you drink. Taking a shower in water with high levels of trihalomethanes can cause health problems, too. A ten minute shower can lead you to absorbing more trihalomethanes than you would by drinking 5 glasses of water.

What is being done

      In order to reduce the effects of trihalomethanes, rules have been set in place by the government of Canada. The maximum allowable annual average level of all trihalomethanes in total is 80 parts per billion. The maximum allowed concentration is 100 micrograms per litre.

     One way that water treatment plants reduce the levels and concentration of trihalomethanes is by using a chloroamine disinfectant instead instead of chlorine. Chloroamines are formed by adding ammonia (NH3) to chlorination systems. Chloroamines do not react with organic matter to form trihalomethanes, and it is not expensive for treatment plants to switch. However, they are less effective as disinfectants than chlorine, so greater levels must be used to treat our water. Also, chloroamine cannot be present in the water used in fish aquariums and in kidney dialysis. When disinfectants are switched from chlorine to chloroamine disinfectants, the water will begin to have more colour. This colour comes from the organic matter in water and because chloroamines do not react with the organic matter, the colour will show up in the water.

     Some other methods that they use to reduce the amount of trihalomethanes in our water is by removing organic material from the water before the water is disinfected, reducing the amount of chlorine being used to disinfect the water, and using disinfectants other than chlorine, such as ozone or UV light.

     There are also several ways that we can reduce the trihalomethane levels in our home. These include using filters and using reverse osmosis.