Reverse QMRA for Pseudomonas aeruginosa in Premise Plumbing to Inform Risk Management

Pseudomonas aeruginosa is an opportunistic pathogen that can grow and proliferate in biofilms in premise plumbing systems and is capable of causing infections through the ocular, inhalation, and dermal routes of exposure. When the pathogen colonizes showerheads and faucets, there is risk of exposure to contaminated water through the ocular route during hand and face-washing events and the inhalation route during showering events. P. aeruginosa can cause an infection of the lungs, a more severe risk for immunocompromised individuals, and is one of the main causes of bacterial keratitis. A reverse quantitative microbial risk assessment (QMRA) was completed to determine the threshold concentrations of P. aeruginosa associated with the US Environmental Protection Agency's maximum allowable risk for waterborne pathogens of 1 infection in 10,000 persons per year. The ocular exposure route poses a more significant risk of infection to the average user at the tap, as indicated by the median threshold concentrations of 6.04x1011, 0.92, and 37 colony forming units (CFU) per liter for the showering, face-washing, and handwashing events, respectively. The reverse QMRA methodology followed in this analysis provides distributions of concentrations of concern that will aid decision makers in prioritizing mitigation strategies and monitoring plans for premise plumbing systems.