Dear WDDTY

I write in reference to Deanne Pearson's article "Poison in the Pool" in your July issue (vol 6 no 4). While we agree with most of her excellent article, especially the information on the problems with chlorine, we must strongly disagree with her suggestion that ozone is a credible replacement or reducer of the need to use chlorine.

The EEC is at present investigating the byproduct from ozone called bromate. This substance has been proven to produce kidney tumours in rats, and guidelines on drinking water recently published by the World Health Organization classified bromate as a possible human carcinogen. The EEC is considering limiting the level of bromate to 0.5 mg/lt, which would effectively close down every ozone unit.

There are a great many ozones systems closed down in Britain, and most of the ones that are operative are running with the normal free chlorine level of 2-3ppm present. The reason for this is because ozone does not have any residual disinfectant capabilities; it only disinfects in a a closed vessel and not in the pool. Hence, injection of contaminants into the pool by bathers is not handled until the water has passed through the pumps and through the ozone system.

This gives plenty of time for bacteria to multiply and infect bathers before it is treated. William Thompson, Aligator, Nature-friendly Pool Systems, Clacton on Sea, Essex.....