[Legionella pneumophila in pool water].

We investigated 87 samples of pool water for the presence of Legionella. The samples were from cold water pools (< 28 degrees C) and from hot water pools (> 32 degrees C). Sampling was furthermore done on normal water samples, on water from the bottom of pools and of water from departure from the activated carbon filters. Legionella was not detected in any of the samples from cold water pools, whereas in the hot water pools 10% of the pool water samples and 80% of the water from the filters were infected with Legionella pneumophila. The highest concentrations of Legionella were found in the filter samples, whereas the concentrations in the pool water (10-100 cfu/liter) were not alarming. This investigation demonstrates the potential risk of presence of Legionella in hot water pools with activated carbon filters being the site with best growth potential. It should be stressed that a high level of disinfection (at least 1.0 mg free chlorine/liter and pH 7.2) is essential for the prevention of Legionella in pool water at higher temperatures.