For accurate exposure assessment, where should a water sample be collected from?

Collecting a water sample from a faucet without touching the aerator is the correct approach for accurate exposure assessment. This method ensures that the sample reflects the water quality directly from the tap, which is critical for understanding the potential for Legionella exposure. The aerator can trap biofilm and contaminants; touching it could inadvertently introduce other microorganisms or alter the sample's integrity.

By avoiding contact with the aerator, the sample is less likely to be contaminated, allowing for a more reliable assessment of the water quality. This approach helps to identify whether there is a presence of Legionella bacteria in the water supply directly at the point of use, which is essential for effective monitoring and management of Legionella risks in plumbing systems.

Using a hose attached to the faucet might lead to misleading results as it could introduce additional water temperature or content variances that do not reflect the water dispensed directly from the tap. Meanwhile, removing the aerator before sampling can disturb the biofilm and affect the accuracy of the assessment. Collecting from a previously unused cup can also be problematic, as it may not adequately represent the conditions at the point of use and might introduce additional variables into the sampling process. Thus, collecting directly from the faucet is the most effective method for obtaining