Predicting health risk due to Legionella pneumophila bacteria while showering

To attain a sustainable water policy the use of alternative water resources is considered and the use of hot water temperatures lower than 60 °C to reduce energy use. Both scenarios, however, come with potential health risks as they give rise to an increase of bacteria in the water. These bacteria can be released into the air via aerosolization and can then be inhaled causing infection.

To quantify the potential health risk it is necessary to know the amount of bacteria to which humans are exposed due to aerosolization. The aim of this study is to simulate this amount of bacteria present in air. The focus is specifically on the bacterium of Legionella pneumophila for the case-study of a shower in an office building. Building upon an existing validated simulation model that predicts the growth of Legionella pneumophila in water systems in buildings (Van Kenhove et al. 2019), this study extends the existing model to account for the aerosolization process during showering.

This way the model will also simulate the amount of bacteria present in the air during and after showering. A key aspect of this extension involves incorporating a partitioning coefficient to estimate the number of bacteria present in aerosols at showerheads as found in literature (Armstrong and Haas, 2007b, Schoen and Ashbolt, 2011). The results will yield an enhanced simulation model capable of predicting the health risks associated with Legionella pneumophila in showers.

This model can be generalized to different types of showers across various building environments. Future work will expand the model to include additional water use points, such as faucets and toilets, and consider other bacterial species. This research contributes to the development of more comprehensive risk assessments based on simulations and predictions, which are crucial for formulating effective water management policies that prioritize both sustainability and public health.