Children, the environment and cancer

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Specific environmental contaminants - VI

Chlorinated water



Better methods of water treatment

Chlorine disinfection by-products are caused by:

• the amount of chlorine used to disinfect the water
• chlorine reacting with the organic matter, such as plant matter, in the water

The amount of chlorine used could be decreased by using a combination of methods. For example, water treatment facilities may be able to use better filtration or better placement of water intake pipes, along with UV light treatment to disinfect the water.

Some municipalities use groundwater (such as underground wells) that generally contains less organic matter. Some municipalities draw from surface water sources, but can draw from relatively clean sources, like large lakes, using intake pipes placed deep and far from shore. Other communities must get their water from smaller lakes and rivers that naturally tend to contain more organic matter, and this may result in higher levels of THMs and HAAs in their tap water. This is usually taken into account when setting the procedures for the local water treatment plant, and for the water quality monitoring (both of the untreated water, and the water during and after the treatment).


Aside from naturally-occurring organic matter such as dead leaves and soil in untreated water, run-off from farms (e.g. manure, fertilizers) and other places can further contaminate water sources. Both surface and ground water can be contaminated by run-off from homes and businesses. Protection of areas near water sources can reduce the amount of disinfection by-products created by:

• reducing the amount of organic matter in the untreated water



• reducing the amount of chlorine needed to treat the water

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