The impact of water flow rates on bioaerosol production from handwashing basins

• Aerosols from handwashing basins can cause healthcare-associated infections. • Respirable aerosols were generated from contaminated drain. • Aerosol and droplet dispersion increased as flow rate decreased. • Low flow rates increased water pressure, generating more aerosols upon drain impact. • Findings stress need for research on design to reduce infection risks. Bioaerosols within the built environment pose a potential risk to public health. In healthcare settings, aerosols generated from handwashing basins have been receiving increasing attention due to their role in healthcare-associated infection outbreaks. Currently, there is limited knowledge regarding the impact of hand basin design parameters on bioaerosol production and transmission routes to patients. This study used a model hand basin system to investigate the effect of different flow rate restrictors on the number, size and distribution of bioaerosols produced. Source water was spiked with Escherichia coli and the hand basin drain seeded with Staphylococcus epidermis as indicator bacteria to facilitate tracking of the bioaerosol source. All three flow restrictors utilised generated bioaerosols of respirable size with no significant difference in the number of aerosols and droplets from the source water across different flow rates. However, lower flow rates led to a higher generation of aerosols from the drain and increased retrograde contamination from the drain to faucet compared to higher flow rates. These findings suggest that modifying design elements, such as aerator design and flow rates, could potentially reduce infection risks, but the optimal configuration remains unclear. This highlights the need for future collaborative research between product designers, engineers and microbiologists to inform optimum design and ensure functional needs are met whilst protecting occupants in healthcare and other high health-risk built environments.