INvestigating Home water and Aerosols' Links to opportunistic pathogen Exposure (INHALE): do consumer decisions impact pathogen exposure and virulence?

As people take showers, they are exposed to billions of bacterial cells through contact with the water and inhalation of produced aerosols. While many of these organisms are harmless, some drinking water-associated pathogens (DWPIs) are a leading cause of serious health risks, especially for individuals with weakened immune systems. Today, the showerhead market in the United States features a wide range of options which leave consumers to select the type of spray pattern, material, flow rate, and additives (e.g., bacterial killing chemicals) that they want to have in their shower systems.

However, we have a limited fundamental understanding of how consumer choices of showerheads directly influence the presence and amounts of DWPIs in shower water and shower water produced aerosols. The overarching goal of this project is to address this knowledge gap. To advance this goal, the Principal Investigators (PIs) will test showerheads with different spray patterns, water flow rates, and additives in an experimental shower lab with the goal of measuring and comparing the concentrations of DWPIs present in shower water and shower water produced aerosols.

The successful completion of this project will benefit society through the generation of new data and fundamental knowledge that could enable consumers to select showerheads that prioritize their health while enhancing the fundamental understanding of the aerosolization of DWPIs in shower systems and the built environment. Additional benefits to society will be achieved through student education and training including the mentoring of one graduate student and one undergraduate student at the University of Pittsburgh.

Pulmonary infections from drinking water-associated pathogens predominantly causing infections in immunocompromised individuals (DWPI) are a leading cause of morbidity and mortality in the United States. Although there are many DWPIs, Legionella pneumophila, nontuberculous mycobacteria (NTM) and Pseudomonas aeruginosa are estimated to cost the United States economy $2.39 billion annually.

Although DWPI exposure can occur through a variety of pathways, inhalation of water associated aerosols are most associated with infection. Aerosolization, a critical step in the transmission pathway of DWPIs, remains poorly understood. Specifically, little is known about how consumer showerhead choices (spray pattern, flow rate, and material additives) influence DWPI virulence and partitioning from the water to aerosol phase.

The long-term goals of this study are to quantitively assess the DWPI exposure risk posed by aerosols produced by different showerhead setups and ascertain if different setups select for greater DWPI exposure and more virulent DWPIs. This goal will be achieved through two research objectives. Objective 1 will test a range of different showerhead setups in an experimental shower lab and quantify the abundance of live L. pneumophila, P. aeruginosa, and NTM in shower water and its associated aerosols using ddPCR and develop shower water to aerosol partitioning models for each DWPI and showerhead.

Objective 2 will use a combination of genomic, kinetic, biofilm aggregation, and macrophage infectivity assays to investigate the role that showerhead setup has on organism fitness and virulence. The successful completion of this research has the potential for transformative impact through the generation of new data and fundamental knowledge including mechanistic models of exposure and risk to human health related to the presence of DWPIs in shower water and shower water produced aerosols.

To implement the education and training goals of the project, the PIs propose to leverage existing programs at the University of Pittsburgh (U Pitt) Swanson School of Engineering such as the EXCEL program to recruit and mentor undergraduate students from underrepresented groups to work on the project. In addition, the PIs plan to integrate the project research findings into relevant undergraduate and graduate courses at U Pitt.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.