Persistence of Bowl Water Contamination during Sequential Flushes of Contaminated Toilets.

Toilets contaminated with infectious organisms are a recognized contact disease transmission hazard. Previous studies indicate that toilet bowl water can remain contaminated for several flushes after the contamination occurs. This study characterized contamination persistence over an extended series of flushes using both indicator particles and viable bacteria. For this study, toilets were seeded with microbe-size microbial surrogates and with Pseudomonas fluorescens or Clostridium difficile bacteria and flushed up to 24 times. Bowl water samples collected after seeding and after each flush indicated the clearance per flush and residual bowl water contaminant concentration. Toilets exhibited 3 + log10 contaminant reductions with the first flush, only 1-2 logs with the second flush, and less than 1 log thereafter. Contamination still was present 24 flushes post contamination. Clearance was modeled accurately by a two-stage exponential decay process. This study shows that toilet bowl water will remain contaminated many flushes after initial contamination, posing a risk of recurring environmental contamination and associated infection incidence.

Evaluation of engineering controls for the mixing of flavorings containing diacetyl and other volatile ingredients.

Exposures to diacetyl, a primary ingredient of butter flavoring, have been shown to cause respiratory disease among workers who mix flavorings. This study focused on evaluating ventilation controls designed to reduce emissions from the flavor mixing tanks, the major source of diacetyl in the plants. Five exhaust hood configurations were evaluated in the laboratory: standard hinged lid-opened, standard hinged lid-closed, hinged lid-slotted, dome with 38-mm gap, and dome with 114-mm gap. Tracer gas tests were performed to evaluate quantitative capture efficiency for each hood. A perforated copper coil was used to simulate an area source within the 1.2-meter diameter mixing tank. Capture efficiencies were measured at four hood exhaust flow rates (2.83, 5.66, 11.3, and 17.0 cubic meters per min) and three cross draft velocities (0, 30, and 60 meters per min). All hoods evaluated performed well with capture efficiencies above 90% for most combinations of exhaust volume and cross drafts. The standard hinged lid was the least expensive to manufacture and had the best average capture efficiency (over 99%) in the closed configuration for all exhaust flow rates and cross drafts. The hinged lid-slotted hood had some of the lowest capture efficiencies at the low exhaust flow rates compared to the other hood designs. The standard hinged lid performed well, even in the open position, and it provided a flexible approach to controlling emissions from mixing tanks. The dome hood gave results comparable to the standard hinged lid but it is more expensive to manufacture. The results of the study indicate that emissions from mixing tanks used in the production of flavorings can be controlled using simple inexpensive exhaust hoods.

Short-term monitoring of formaldehyde: comparison of two direct-reading instruments to a laboratory-based method.

Airborne formaldehyde concentrations can be measured using several different techniques, including laboratory-based methods and direct-reading instruments. Two commercially available direct-reading instruments, an RKI Instruments Model FP-30 and a PPM Technology Formaldemeter htV, were compared with National Institute for Occupational Safety and Health Method 2016 in different test environments to determine if these direct-reading instruments can provide comparable results. The methods yielded the following mean concentrations for 47 samples: NIOSH Method 2016, 0.37 ppm; FP-30, 0.29 ppm; and htV, 0.34 ppm. Results from both of the direct-reading instruments were correlated with the laboratory-based method (R² = 0.78 for FP-30, and 0.902 for htV). Comparison of the means of the three methods showed that on average the FP-30 instrument (p < 0.001) differed statistically from NIOSH Method 2016, whereas the htV (p = 0.15) was not statistically different from the NIOSH method. Sensitivity and specificity tests demonstrated that the FP-30 had sensitivity above 60% to detect formaldehyde concentrations at all the cutoff levels tested, whereas the htV appeared to have greater sensitivity above 88% for the levels evaluated.

Lifting the lid on toilet plume aerosol: a literature review with suggestions for future research.

BACKGROUND: The potential risks associated with "toilet plume" aerosols produced by flush toilets is a subject of continuing study. This review examines the evidence regarding toilet plume bioaerosol generation and infectious disease transmission. METHODS: The peer-reviewed scientific literature was searched to identify articles related to aerosol production during toilet flushing, as well as epidemiologic studies examining the potential role of toilets in infectious disease outbreaks. RESULTS: The studies demonstrate that potentially infectious aerosols may be produced in substantial quantities during flushing. Aerosolization can continue through multiple flushes to expose subsequent toilet users. Some of the aerosols desiccate to become droplet nuclei and remain adrift in the air currents. However, no studies have yet clearly demonstrated or refuted toilet plume-related disease transmission, and the significance of the risk remains largely uncharacterized. CONCLUSION: Research suggests that toilet plume could play a contributory role in the transmission of infectious diseases. Additional research in multiple areas is warranted to assess the risks posed by toilet plume, especially within health care facilities.