SINGAPORE - We thank Mr Pattathil Madhav Menon for his feedback ("Is chlorine level in pools safe?"; June 2).
The use of chlorine for disinfection is an internationally accepted practice to ensure that public pools are safe for use, and minimises the risk of infectious disease outbreaks.
The World Health Organisation (WHO) has recommended that chlorine levels in pools be maintained between 1mg per litre (mg/l) and 3mg/l, in consideration of the need to ensure adequate disinfection while balancing the risk from exposure to potential by-products such as trihalomethanes (THMs) from overdosing of chlorine. The WHO has not set any maximum limits on THMs in pool water.
All licensed public swimming pools are required by the National Environment Agency (NEA) to chlorinate pool water. The operators must ensure that the chlorine level in the pool is maintained within NEA's regulations (between 1mg/l and 3 mg/l).
They are also required to have a monthly sampling programme to ensure that the water quality meets the physical, chemical and bacteriological standards of our regulations.
The tests are carried out by accredited laboratories and these results must be submitted to us. We will also conduct random water sampling of public swimming pools to ensure that these standards are met.
We will continue to monitor best practices adopted by other regulatory agencies and studies concerning THMs in pools in our ongoing review of our swimming pool regulations.
Tai Ji Choong
Director of the Environmental Health Division, National Environment Agency
In answer to the letter:
The use of high-concentration residual chlorine - one to three parts per million - under the local regulatory requirement ensures that swimming pool water is free of pathogens like E. coli ("No E. coli in pools, says NEA").
It is a well-documented fact that trihalomethanes, which are suspected carcinogens, are by-products of chlorine's reaction with organic matter in water.
Most swimmers ingest some amount of pool water, exposing them to the risks posed by trihalomethanes.
Does the National Environment Agency conduct regular tests for trihalomethanes to ensure public safety?
Pattathil Madhav Menon
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