title: Aerosol Generation by Modern Flush Toilets.
abstract: A microbe-contaminated toilet will produce bioaerosols when flushed. We assessed toilet plume aerosol from high efficiency (HET), pressure-assisted high efficiency (PAT), and flushometer (FOM) toilets with similar bowl water and flush volumes. Total and droplet nuclei "bioaerosols" were assessed. Monodisperse 0.25-1.9-μm fluorescent microspheres served as microbe surrogates in separate trials in a mockup 5 m3water closet (WC). Bowl water seeding was approximately 1012particles/mL. Droplet nuclei were sampled onto 0.2-μm pore size mixed cellulose ester filters beginning 15 min after the flush using open-face cassettes mounted on the WC walls. Pre- and postflush bowl water concentrations were measured. Filter particle counts were analyzed via fluorescent microscopy. Bowl headspace droplet count size distributions were bimodal and similar for all toilet types and flush conditions, with 95% of droplets<2μm diameter and>99%<5μm. Up to 145,000 droplets were produced per flush, with the high-energy flushometer producing over three times as many as the lower energy PAT and over 12 times as many as the lowest energy HET despite similar flush volumes. The mean numbers of fluorescent droplet nuclei particles aerosolized and remaining airborne also increased with flush energy. Fluorescent droplet nuclei per flush decreased with increasing particle size. These findings suggest two concurrent aerosolization mechanisms-splashing for large droplets and bubble bursting for the fine droplets that form droplet nuclei.
authors.affiliation: Department of Occupational and Environmental Health, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, USA.
authors.forename: David
authors.initials: D
authors.lastname: Johnson
authors.affiliation: Department of Occupational and Environmental Health, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Lynch
authors.affiliation: Department of Occupational and Environmental Health, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Marshall
authors.affiliation: National Institute for Occupational Safety and Health, Division of Applied Research and Technology, Centers for Disease Control and Prevention, Cincinnati, Ohio, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Mead
authors.affiliation: National Institute for Occupational Safety and Health, Division of Applied Research and Technology, Centers for Disease Control and Prevention, Cincinnati, Ohio, USA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Hirst