Swimming: Chlorate in many swimming pools in Switzerland

Out of 92 swimming pools tested in Switzerland from May to November 2023, some of them fail to permanently respect the maximum value for chemical by-products, containing chlorate. These are linked to the disinfection of bathing water.

In 43 (47%) of the establishments assessed, the concentration of chlorates – chlorate, bromate, perchlorate and trichloroacetate – was higher than the maximum value in at least one of the bathing water samples taken, the association of cantonal chemists said on Monday in a press release.

The proportion exceeding the maximum value was slightly higher for outdoor swimming pools (49%) than for indoor swimming pools (44%).

However, these figures are not representative for Switzerland and the Principality of Liechtenstein, we read further, because the samples were taken mainly in establishments which had already been faced with exceeding the maximum chlorate value in the past.

In 84% of controls, the measures required in the event of exceeding the maximum value were fully or at least partially applied. Companies were therefore visibly striving to improve, assess the chemists. However, in 56% of establishments the maximum value was again exceeded in bathing water.

Regarding the other controlled disinfection by-products (bromate, perchlorate, trichloroacetate), however, there is no need for improvement, or at most a one-off need.

Bathers’ health

For optimal protection of the health of bathers, it is important that bathing establishments strive to keep the concentration of chlorates as low as possible, emphasize the cantonal chemists. In the future, official food control services will take more account of the chlorate by-product in their assessment during swimming pool inspections.

Swimming pools are invited to control chlorates as part of their self-control, although due to the numerous routes of introduction and formation of chlorate in bathing water, it is difficult to implement effective and sustainable measures. No maximum value for these products has been set in the relevant ordinances.

drank, ats