Only small amounts of legionella bacteria found in hot tubs and warm water pools in the capital region

29.11.2022 14.00

The presence of legionella bacteria in hot tubs and warm water pools was examined in Espoo, Helsinki, Vantaa and Central Uusimaa in 2022. During the project, legionella bacteria were only found in one sample.

The aim of the project was to examine the presence of legionella bacteria in hot tubs and warm water pools. At the moment, swimming pools are not regularly tested for legionella bacteria and there is no comprehensive information on their presence in swimming pools.

A total of 32 samples were collected from 23 different locations. Thirteen of the pools and hot tubs were in Helsinki, ten in Espoo, seven in Vantaa and two in Central Uusimaa. The samples were collected from hot tubs and multi-purpose pools at public swimming pools.

Legionella bacteria were only found in one sample, which was collected in Vantaa. No bacteria were found in the follow-up sample.

The project was related to the European Union’s Drinking Water Directive that came into force in 2021 and is currently being implemented in Finland. The directive applies to all water intended for human consumption and sets new requirements for controlling legionella bacteria, among other things.

Regular use and maintenance of water systems and correct water temperature prevent problems

Legionella bacteria can reproduce in water and air conditioning systems and spread into the air through aerosols. Infection typically occurs when a person inhales an aerosol containing legionella bacteria. Cases of legionellosis vary from a mild or asymptomatic respiratory infection to life-threatening pneumonia. Factors that increase the risk of pneumonia include old age, smoking and underlying medical conditions that weaken one’s immune system. Legionellosis cannot be transmitted from one person to another.

Hot tubs and pools with water jets are risk environments in terms of legionella bacteria due to extensive aerosol formation.

Problems caused by legionella bacteria can be prevented by regularly using, maintaining and cleaning the water systems. Water should not stand in pipes for long periods of time, and unused parts of water systems should be removed. The temperature of the water is also important. The temperature of warm water should be 55–65 °C and the temperature of cold water should be no more than 20 °C. A sufficient chlorine content also prevents the growth of legionella bacteria.

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