Document Type


Date of Degree

Spring 2017

Degree Name

MS (Master of Science)

Degree In

Occupational and Environmental Health

First Advisor

Matthew W. Nonnenmann


Infectious diseases account for over 15 million deaths worldwide. Those who are at greatest risk of contracting an infectious disease are immunocompromised. These individuals may be admitted to a healthcare-based setting where they may become infected. In the United States, 1.7 million immunocompromised individuals contract a healthcare-associated infection which lengthens stay, increases medical costs, and puts lives at stake. The transmission routes for these infections occur from direct contact with healthcare staff and contaminated surfaces. Indirect contact methods, such as bioaerosols suggest, but are not a well-examined route of infection. One possible bioaerosol generator includes the flushing of loose stools in toilets from infected patients. To date, no study has investigated the particle or bioaerosol changes in the air resulting from toilet flushing loose fecal wastes in a healthcare setting. The purpose of this study was to investigate changes in the air before and after a toilet flush to support hypotheses that toilets can produce an aerosol containing viable microorganisms, potentially spreading infectious disease.

Particle and bioaerosol concentrations were measured in hospital bathrooms across 3 sampling conditions; no waste no flush, no waste with flush, and fecal waste with flush. Particle concentrations were measured with a particle counter 3 minutes before a flushing event and throughout the bioaerosol collection period. Bioaerosol concentrations were measured with BioStage impactors fixed on a sampling cart at distances of 0.15, 0.5, and 1 m that was placed in front of a toilet. For each sampling trial, 3 time measurements were recorded after a flushing event (i.e., 5, 10, 15 minutes).

Particle concentrations measured before and after the flush were found to be significantly different in 0.3 (p-values= 0.002, 0.002, 0.015), 0.5 (p-values= 0.002, 0.002, 0.018), 1 (p-values= 0.003, 0.003, 0.027), and 3 µm (p-values= 0.016, 0.032) size bins of the no waste with flush and 0.3 (p-values= 0.009, 0.007, 0.007), 0.5 (p-values= 0.018, 0.006, 0.004), 1 µm (p-values= 0.023, 0.013,) size bins of the fecal waste with flush conditions. Bioaerosol concentrations measured in the no waste no flush and fecal waste with flush were found to be significantly different (p-value= 0.005). However, the bioaerosol concentrations measured were not significantly different across time (p-value= 0.977) or distance (p-value= 0.911).

From the study, we concluded that toilets in this unit produce particles when flushed. The particles aerosolized include microorganisms remaining from previous use or from loose fecal wastes. Differences in bioaerosol concentrations across conditions also suggest that toilets flushed containing wastes may be a likely source of bioaerosols that could allow transmission of infectious microorganisms. No observed differences across time and distance of bioaerosol concentrations suggests that generated aerosols quickly diffuse in the air. Since this study is the first to quantify particles and bioaerosols produced from flushing a hospital toilet, future studies are needed for comparison and for intervention development.


viii, 74 pages


Includes bibliographical references (pages 68-74).


Copyright © 2017 Samantha Dawn Knowlton