Toilet plume aerosol generation rate and environmental contamination following bowl water inoculation with Clostridium difficile spores.

INTRODUCTION: Clostridium difficile is the leading cause of health care-associated gastric illness. Environmental contamination with C difficile spores is a risk factor for contact transmission, and toilet flushing causes such contamination. This work explores toilet contamination persistence and environmental contamination produced over a series of flushes after contamination. METHODS: A flushometer toilet was seeded with C difficile spores in a sealed chamber. The toilet was flushed 24times, with postflush bowl water samples and settle plates periodically collected for culturing and counting. Air samples were collected after each of 12 flushes using rotating plate impactors. RESULTS: Spores were present in bowl water even after 24 flushes. Large droplet spore deposition accumulated over the 24-flush period. Droplet nuclei spore bioaerosol was produced over at least 12 flushes. CONCLUSIONS: Toilets contaminated with C difficile spores are a persistent source of environmental contamination over an extended number of flushes.

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.

Key contributors to variations in fish mercury within and among freshwater reservoirs in Oklahoma, USA.

Elevated fish mercury (Hg) concentrations in freshwater ecosystems worldwide are a significant human and ecological health concern. Mercury bioaccumulation and biomagnification in lakes and reservoirs are controlled by numerous biogeochemical and ecological factors, contributing to variability in fish Hg concentrations both within and among systems. We measured total mercury concentrations ([THg]) and stable isotopes (δ(15)N, δ(13)C) in over 30 fish species in two connected subtropical freshwater reservoirs (Grand Lake and Lake Hudson, Oklahoma, USA), their tributaries, and local farm ponds, all of which are potentially impacted by nearby atmospheric Hg sources. We also conducted an inter-system analysis among 61 reservoirs in Oklahoma to explore biological, chemical and physical factors associated with fish [THg] across systems. We found that [THg] for most species in Grand Lake and Lake Hudson were relatively low compared to other reservoirs in Oklahoma. There were significant spatial variations in many species within and between Grand Lake and Lake Hudson, even after accounting for length and/or trophic position (based on δ(15)N). Fish in local farm ponds, commonly used in agricultural regions for raising game fish, had 2-17 times higher [THg] than fish of a similar length in nearby reservoirs. The inter-system analysis revealed that pH, water color, rainfall, and nutrients are the best predictors of fish [THg] across systems. Our results provide insight into the key factors associated with fish [THg] variations both within and across systems, and may be useful for exposure assessment and for identifying sites and water bodies prone to high fish [THg] as monitoring priorities.

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.

The effect of pressure differential and care provider movement on airborne infectious isolation room containment effectiveness.

BACKGROUND: Airborne infectious isolation rooms (AIIRs) are maintained at a negative pressure relative to surrounding areas to prevent migration of potentially infectious droplet nuclei. Current US design standards require a pressure differential of only 2.5 Pascals (Pa), compared with 15 Pa in some other countries. The purpose of this work was to compare containment efficiency in a properly designed anteroom-equipped hospital AIIR at differential pressures ranging from 2.5 to 20 Pa under conditions of no provider traffic and simulated high provider traffic. METHODS: Fluorescent microspheres were released into the AIIR to simulate infectious droplet nuclei. Airborne concentrations were measured inside the AIIR, in the anteroom, and at the corridor-anteroom door both with and without care provider movement through the AIIR under differential pressure conditions of 2.5, 11, and 20 Pa. Particles were collected by air sampling onto filters, with enumeration via fluorescent microscopy. RESULTS: Reduced containment effectiveness during provider traffic was observed, consistent with previous studies. Containment increased with increasingly negative pressure differential and decreased with increasing provider traffic. CONCLUSIONS: Provider traffic adversely affected containment. Containment improved with an increasing pressure differential. The anteroom plays an important role in limiting net particle escape, especially during provider movement through the space.

Containment effectiveness of expedient patient isolation units.

BACKGROUND: It is generally recognized that the health care system does not have adequate isolation capacity to meet the surge in demand during a major outbreak of airborne infectious disease. Alternatives to engineered isolation rooms undoubtedly will be required as surge isolation requirements exceed the available resources. The purpose of this work was to estimate containment efficiency of expedient airborne infectious isolation units with and without anterooms in the absence and presence of care provider traffic. METHODS: Fluorescent 2-microm aerosol particles were released into the interior of expedient-construction isolation modules exhausted with a high-efficiency particulate air (HEPA)-filtered fan unit. Particle concentrations inside and outside the enclosure were measured with and without provider traffic simulated with a mannequin. Measurements were obtained on modules constructed with and without an anteroom, which was not separately ventilated. RESULTS: Containment estimates were excellent for all isolation configurations evaluated, generally exceeding 99.7%. Particle escape was statistically significantly higher with simulated traffic than without; however, there was no statistically significant difference in particle escape with and without an anteroom. CONCLUSION: Our findings demonstrate that effective isolation may be possible using low-technology, low-cost, easily built structures that can be readily constructed within hospital and other environments in emergency response situations.

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 technique's 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.

Recurrent critical violations of the food code in retail food service establishments.

Records of restaurant inspections by public health departments provide sequential "snapshots" of conditions in retail food service establishments that can be used to identify risk factors and evaluate the effectiveness of interventions. Data from a random 10 percent sample of restaurant inspection files from 31 counties in Oklahoma, including 4,044 inspections conducted during 1996-2000 in "medium-risk" and "high-risk" establishments, were analyzed to determine rates of critical violations and recurrent violations for different categories of establishments. Repeat violations accounted for about half of all violations. Establishments subjectively designated as high risk by health department personnel were in fact found to have higher violation rates than those described as medium-risk establishments. Outside Oklahoma County, regional chain restaurants were significantly more likely than other restaurants to have recurrent violations of critical items related to food-holding temperature, hygiene practices, sanitization, and hygiene facilities. Differences observed in violation rates among individual establishments were not primarily attributable to inconsistent enforcement by individual inspectors; rather, they appeared to be indicative of real differences in hygienic conditions and practices.

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.

A comparison of food safety knowledge among restaurant managers, by source of training and experience, in Oklahoma County, Oklahoma.

The annual incidence of illness related to food consumption continues to present a challenge to environmental health management. A significant fraction of cases have been attributed to consumption of food in restaurants, and as the number of meals eaten away from the home continues to rise, the potential for large-scale foodborne-disease outbreaks will continue to increase. Food handlers in retail establishments contribute to the incidence of foodborne disease; therefore, it is essential that workers and management staff have a thorough understanding of safe food practices. Since the training, certification, and experience of food service managers vary greatly, it is also likely that managers' knowledge base may differ. In the study reported here, restaurant managers were administered a survey designed to measure their understanding of basic food safety principles. The sources of training, certification, and experience were found to significantly affect the level of food safety knowledge; however, increased hours of training did not increase knowledge. In addition, the time lapsed since training did not significantly affect the level of knowledge.

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.

Lead sources, behaviors, and socioeconomic factors in relation to blood lead of native american and white children: a community-based assessment of a former mining area.

Lead poisoning prevention requires knowledge of lead sources and of appropriate residential lead standards. Data are severely lacking on lead sources for Native American children, many of whom live in rural areas. Further, the relation of mining waste to blood lead concentrations (BPbs) of rural children is controversial. In collaboration with the eight tribes of northeastern Oklahoma, we assessed lead sources and their effects on BPbs for rural Native American and White children living in a former mining region. Venous blood lead, residential environmental (soil, dust, paint, water), and caregiver interview (e.g., hand-to-mouth behaviors, socioeconomic conditions) data were obtained from a representative sample of 245 children 1-6 years of age. BPbs ranged from 1 to 24 microg/dL. There were no ethnic differences in BPbs (p= 0.48) nor any patterns of excess lead sources for Native American or White children. Multiple linear regression analyses indicated that mean soil lead, mean floor lead loading, mouthing behaviors, caregivers' education, and residence in former mining towns were all strongly associated with BPbs. Logistic regression results showed mean floor dust lead loading greater than or equal to 10.1 microg/ft(2) (odds ratio [OR], 11.4; 95% confidence interval [CI], 3.5-37.3), and yard soil lead >165.3 mg/kg (OR, 4.1; CI, 1.3-12.4) were independently associated with BPbs greater than or equal to 10 microg/dL. We also found strong interactions between soil lead and poverty (p= 0.005), and dust and soil sources (p= 0.02). Our findings indicate that soil and dust lead derived largely from mining waste pose a health hazard to Native American and White children, and that current residential dust lead standards are insufficient to adequately protect children. Moreover, our finding that poor children are especially vulnerable to lead exposures suggests that residential standards should consider interactions among socioeconomic conditions and lead sources if environmental justice is to be achieved.