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Aerosol generation by modern flush toilets.
Johnson D; Lynch R; Marshall C; Mead K; Hirst D
Aerosol Sci Tech 2013 Sep; 47(9):1047-1057
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-um fluorescent microspheres served as microbe surrogates in separate trials in a mockup 5 m3 water closet (WC). Bowl water seeding was approximately 1012 particles/mL. Droplet nuclei were sampled onto 0.2-umpore sizemixed cellulose ester filters beginning 15 min after the flush using open-face cassettesmounted 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<2 um diameter and>99%<5 um. 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.
Microorganisms; Aerosol-particles; Aerosols; Biological-agents; Exposure-levels; Risk-factors; Particulates; Air-sampling; Airborne-particles; Air-contamination
David Johnson, Department of Occupational and Environmental Health, University of Oklahoma Health Science Center, P.O. Box 26901, CHB Room 139E, Oklahoma City, OK 73126-0907
Issue of Publication
Aerosol Science and Technology
University of Oklahoma Health Sciences Center - Oklahoma City
Page last reviewed: April 1, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division