Robert A. Lynch

The relationship of particle size to olfactory nerve uptake of a non-soluble form of manganese into brain.

The essential element, manganese, can produce chronic neuromotor impairment related to basal ganglia (BG) damage when it is presented in excessive quantities. The uptake and elimination patterns of manganese following ingestion have been well studied and, under normal conditions, excretion appears to keep manganese levels under tight control. Less is known about inhalation exposure, but it has been proposed that the lung might serve as a long-term reservoir for manganese transport into blood. Recent data suggest that a third route of exposure, transport by the olfactory nerve directly to the brain, might have importance in toxicology since such a route would bypass liver uptake and biliary excretion of manganese. In this study, we sought to determine how particle size and the use of a poorly soluble form of manganese might influence net systemic absorption of manganese dust and the potential role of the olfactory nerve in transport of manganese dioxide. Rats were exposed in nose-only exposure chambers to manganese dioxide (MnO2) aerosols of 1.3 and 18 microm mass median aerodynamic diameter (MMAD). The concentration of aerosols was kept constant at 3 mg/m3 as Mn. Following 15 days of exposure (five times per week for 3 weeks), rats were euthanized and tissues harvested for manganese determination carried out by graphite furnace atomic absorption spectroscopy. Small-particle MnO2 exposure resulted in an elevation in olfactory bulb manganese concentration, presumably through uptake by the olfactory nerve, but the effect was highly variable. While small increases in cortical and neostriatal manganese levels were also observed in these rats, they did not reach statistical significance. By contrast, there was no evidence of olfactory nerve MnO2 uptake in rats receiving the large-particle exposure.

A preliminary evaluation of the effect of glove use by food handlers in fast food restaurants

A study was conducted to determine whether the levels of selected microorganisms differed on foods handled by gloved and bare hands at fast food restaurants. Three hundred seventy-one plain flour tortillas were purchased from fast food restaurants and analyzed for Staphylococcus aureus, Escherichia coli, Klebsiella sp., coliform bacteria, and heterotrophic plate count bacteria. Approximately 46% of the samples were handled by workers wearing gloves compared with 52% of samples with bare hand contact. Coliform bacteria were found in 9.6% of samples handled by gloved workers and 4.4% of samples handled by bare hands, although this difference was not statistically significant. The distribution of heterotrophic plate count bacteria, a general measure of hygiene, was also higher in samples handled by gloved workers in one restaurant chain. The presence of E. coli, Klebsiella sp., and S. aureus was detected in one, two, and eight samples, respectively, and there were no significant differences between samples handled by gloved or bare hands. Neither direct contact of the tortilla with the food preparation surface nor gender of the worker affected the level of any organism tested. The observed tendency of food workers to wear the same pair of gloves for extended periods and complacency might account for the apparent failure of gloves to reduce or prevent bacterial contamination. The results further suggest that glove use might be counterproductive because workers might wash their hands less frequently when gloved.

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.

Aerosol Generation by Modern Flush Toilets.

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 m3 water closet (WC). Bowl water seeding was approximately 1012 particles/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 <2 μm diameter and >99% <5 μm. 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. Copyright 2013 American Association for Aerosol Research

An Efficient Analytical Method for Particle Counting in Evaluating Airborne Infectious Isolation Containment Using Fluorescent Microspheres

The containment performance of patient isolation enclosures, particularly expedient surge capacity enclosures, must be verified to protect health care providers and staff, other patients, and hospital visitors. Tracer gas methods are often used, but requirements for special equipment and training limit the techniques utility. A technologically simple yet accurate and precise particle-based technique is needed to measure the low count concentrations of escaping airborne particles that might be present outside an isolation enclosure. Reported here is the performance of such a technique employing micrometer-sized fluorescent polystyrene latex microspheres as a surrogate for pathogenic bioaerosols. Particles are released into the isolation enclosure, air is sampled inside and outside the room to capture airborne particles on 25 mm diameter filters, and the number of particles deposited on a filter is quantified using an optimized random field counting approach. The technique accurately estimates the number of surrogate bioaerosol particles on the filter, allowing calculation of the airborne particle concentrations inside and outside the enclosure, and the containment efficiency. This technique can be employed using generally available equipment and inexpensive supplies and also can minimize the number of particle counts that must be performed. The method is shown to be specific, sensitive, and accurate.