Bioaerosol exposure to personnel in a clinical environment absent patients.

Nosocomial infections pose a significant and escalating threat to both patients and healthcare workers (HCWs). By their nature, hospitals induce antibiotic resistance in virulent and commensal strains, leading to increasingly severe hospital-acquired infections. This study measured environmental exposure experienced by domestic staff cleaning vacated patient rooms of a community hospital to bacteria in ambient bioaerosols. While they cleaned the room, participants wore an N95 filtering facepiece respirator (FFR), from which coupons were cut and bacteria were extracted, cultured and enumerated. Extrapolation to the full area of the respirator yielded measured exposures of 0.2-1.4 × 10(4) colony-forming units/hour, of which ∼97% collected on the front layer of the N95, suggesting a possible role for minimal respiratory protection in nonpatient environments. Random resistance testing of 1.6% of the isolates showed that ∼70% of both Gram-positive and Gram-negative organisms exhibited resistance to oxacillin and ∼9% of the Gram-positives displayed resistance to vancomycin. These data provide an estimate for mask bioaerosol loading that can be used in risk modeling and to refine strategies for reuse of FFRs during critical shortages.

Capture of 0.1-µm aerosol particles containing viable H1N1 influenza virus by N95 filtering facepiece respirators.

Nosocomial infections pose an escalating threat to both patients and healthcare workers (HCWs). A widely recommended device for individual respiratory protection, the N95 filtering facepiece respirator (FFR) has been shown to provide efficient filtration of inert particles larger and smaller than the nominal most-penetrating particle size (MPPS) range, 0.03-0.3 µm. Humans generate respiratory aerosols in the MPPS range, suggesting that short-range disease transmission could occur via small infectious particles. Data presented here show that the N95 FFR will afford a significant measure of protection against infectious particles as small as a bare H1N1 influenza virion, and that the capture mechanism does not discriminate in favor of, or against, biological particles.

Correlation of respirator fit measured on human subjects and a static advanced headform.

This study assessed the correlation of N95 filtering facepiece respirator (FFR) fit between a Static Advanced Headform (StAH) and 10 human test subjects. Quantitative fit evaluations were performed on test subjects who made three visits to the laboratory. On each visit, one fit evaluation was performed on eight different FFRs of various model/size variations. Additionally, subject breathing patterns were recorded. Each fit evaluation comprised three two-minute exercises: "Normal Breathing," "Deep Breathing," and again "Normal Breathing." The overall test fit factors (FF) for human tests were recorded. The same respirator samples were later mounted on the StAH and the overall test manikin fit factors (MFF) were assessed utilizing the recorded human breathing patterns. Linear regression was performed on the mean log10-transformed FF and MFF values to assess the relationship between the values obtained from humans and the StAH. This is the first study to report a positive correlation of respirator fit between a headform and test subjects. The linear regression by respirator resulted in R(2) = 0.95, indicating a strong linear correlation between FF and MFF. For all respirators the geometric mean (GM) FF values were consistently higher than those of the GM MFF. For 50% of respirators, GM FF and GM MFF values were significantly different between humans and the StAH. For data grouped by subject/respirator combinations, the linear regression resulted in R(2) = 0.49. A weaker correlation (R(2) = 0.11) was found using only data paired by subject/respirator combination where both the test subject and StAH had passed a real-time leak check before performing the fit evaluation. For six respirators, the difference in passing rates between the StAH and humans was < 20%, while two respirators showed a difference of 29% and 43%. For data by test subject, GM FF and GM MFF values were significantly different for 40% of the subjects. Overall, the advanced headform system has potential for assessing fit for some N95 FFR model/sizes.

Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.

BACKGROUND: Decontamination, cleaning, and reuse of filtering facepiece respirators (FFRs) has been proposed to mitigate an acute FFR shortage during a public health emergency. Our study evaluates the ability of commercially available wipe products to clean FFRs contaminated with either infectious or noninfectious aerosols. METHODS: Three models of surgical N95 FFRs were contaminated with aerosols of mucin or viable Staphylococcus aureus then cleaned with hypochlorite, benzalkonium chloride, or nonantimicrobial wipes. After cleaning, FFRs were separated into components (nose pad, fabrics, and perforated strip), and contaminants were extracted and quantified. Filtration performance was assessed for cleaned FFRs. RESULTS: Mucin removal was <1 log for all wipe products on all components. Inert wipes achieved ∼1-log attenuation in viable S aureus on fabrics from all FFR models--removal was less effective from nose pads and perforated edges. Both antimicrobial wipes achieved 3-5-log attenuation on most components, with smaller reductions on nose pads and greater reductions on perforated strips. Particle penetration following cleaning yielded mean values <5%. The highest penetrations were observed in FFRs cleaned with benzalkonium chloride wipes. CONCLUSIONS: FFRs can be disinfected using antimicrobial wipe products, but not effectively cleaned with the wipes evaluated in this study. This study provides informative data for the development of better FFRs and applicable cleaning products.

Development of an advanced respirator fit-test headform.

Improved respirator test headforms are needed to measure the fit of N95 filtering facepiece respirators (FFRs) for protection studies against viable airborne particles. A Static (i.e., non-moving, non-speaking) Advanced Headform (StAH) was developed for evaluating the fit of N95 FFRs. The StAH was developed based on the anthropometric dimensions of a digital headform reported by the National Institute for Occupational Safety and Health (NIOSH) and has a silicone polymer skin with defined local tissue thicknesses. Quantitative fit factor evaluations were performed on seven N95 FFR models of various sizes and designs. Donnings were performed with and without a pre-test leak checking method. For each method, four replicate FFR samples of each of the seven models were tested with two donnings per replicate, resulting in a total of 56 tests per donning method. Each fit factor evaluation was comprised of three 86-sec exercises: "Normal Breathing" (NB, 11.2 liters per min (lpm)), "Deep Breathing" (DB, 20.4 lpm), then NB again. A fit factor for each exercise and an overall test fit factor were obtained. Analysis of variance methods were used to identify statistical differences among fit factors (analyzed as logarithms) for different FFR models, exercises, and testing methods. For each FFR model and for each testing method, the NB and DB fit factor data were not significantly different (P > 0.05). Significant differences were seen in the overall exercise fit factor data for the two donning methods among all FFR models (pooled data) and in the overall exercise fit factor data for the two testing methods within certain models. Utilization of the leak checking method improved the rate of obtaining overall exercise fit factors ≥100. The FFR models, which are expected to achieve overall fit factors ≥ 100 on human subjects, achieved overall exercise fit factors ≥ 100 on the StAH. Further research is needed to evaluate the correlation of FFRs fitted on the StAH to FFRs fitted on people. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a file providing detailed information on the advanced head form design and fabrication process.].

Challenge of N95 filtering facepiece respirators with viable H1N1 influenza aerosols.

OBJECTIVE. Specification of appropriate personal protective equipment for respiratory protection against influenza is somewhat controversial. In a clinical environment, N95 filtering facepiece respirators (FFRs) are often recommended for respiratory protection against infectious aerosols. This study evaluates the ability of N95 FFRs to capture viable H1N1 influenza aerosols. METHODs. Five N95 FFR models were challenged with aerosolized viable H1N1 influenza and inert polystyrene latex particles at continuous flow rates of 85 and 170 liters per minute. Virus was assayed using Madin-Darby canine kidney cells to determine the median tissue culture infective dose (TCID50). Aerosols were generated using a Collison nebulizer containing H1N1 influenza virus at 1 x 10(8) TCID50/mL. To determine filtration efficiency, viable sampling was performed upstream and downstream of the FFR. RESULTS. N95 FFRs filtered 0.8-µm particles of both H1N1 influenza and inert origins with more than 95% efficiency. With the exception of 1 model, no statistically significant difference in filtration performance was observed between influenza and inert particles of similar size. Although statistically significant differences were observed for 2 models when comparing the 2 flow rates, the differences have no significance to protection. CONCLUSIONS. This study empirically demonstrates that a National Institute for Occupational Safety and Health-approved N95 FFR captures viable H1N1 influenza aerosols as well as or better than its N95 rating, suggesting that a properly fitted FFR reduces inhalation exposure to airborne influenza virus. This study also provides evidence that filtration efficiency is based primarily on particle size rather than the nature of the particle's origin.

Effects of relative humidity and spraying medium on UV decontamination of filters loaded with viral aerosols.

Although respirators and filters are designed to prevent the spread of pathogenic aerosols, a stockpile shortage is anticipated during the next flu pandemic. Contact transfer and reaerosolization of collected microbes from used respirators are also a concern. An option to address these potential problems is UV irradiation, which inactivates microbes by dimerizing thymine/uracil in nucleic acids. The objective of this study was to determine the effects of transmission mode and environmental conditions on decontamination efficiency by UV. In this study, filters were contaminated by different transmission pathways (droplet and aerosol) using three spraying media (deionized water [DI], beef extract [BE], and artificial saliva [AS]) under different humidity levels (30% [low relative humidity {LRH}], 60% [MRH], and 90% [HRH]). UV irradiation at constant intensity was applied for two time intervals at each relative humidity condition. The highest inactivation efficiency (IE), around 5.8 logs, was seen for DI aerosols containing MS2 on filters at LRH after applying a UV intensity of 1.0 mW/cm(2) for 30 min. The IE of droplets containing MS2 was lower than that of aerosols containing MS2. Absorption of UV by high water content and shielding of viruses near the center of the aggregate are considered responsible for this trend. Across the different media, IEs in AS and in BE were much lower than in DI for both aerosol and droplet transmission, indicating that solids present in AS and BE exhibited a protective effect. For particles sprayed in a protective medium, RH is not a significant parameter.

Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.

Filtering facepiece respirators (FFRs) are recommended for use as precautions against airborne pathogenic microorganisms; however, during pandemics demand for FFRs may far exceed availability. Reuse of FFRs following decontamination has been proposed but few reported studies have addressed the feasibility. Concerns regarding biocidal efficacy, respirator performance post decontamination, decontamination cost, and user safety have impeded adoption of reuse measures. This study examined the effectiveness of three energetic decontamination methods [ultraviolet germicidal irradiation (UVGI), microwave-generated steam, and moist heat] on two National Institute for Occupational Safety and Health-certified N95 FFRs (3M models 1860s and 1870) contaminated with H5N1. An aerosol settling chamber was used to apply virus-laden droplets to FFRs in a method designed to simulate respiratory deposition of droplets onto surfaces. When FFRs were examined post decontamination by viral culture, all three decontamination methods were effective, reducing virus load by > 4 log median tissue culture infective dose. Analysis of treated FFRs using a quantitative molecular amplification assay (quantitative real-time polymerase chain reaction) indicated that UVGI decontamination resulted in lower levels of detectable viral RNA than the other two methods. Filter performance was evaluated before and after decontamination using a 1% NaCl aerosol. As all FFRs displayed <5% penetration by 300-nm particles, no profound reduction in filtration performance was caused in the FFRs tested by exposure to virus and subsequent decontamination by the methods used. These findings indicate that, when properly implemented, these methods effectively decontaminate H5N1 on the two FFR models tested and do not drastically affect their filtering function; however, other considerations may influence decisions to reuse FFRs.

Methyl salicylate: a reactive chemical warfare agent surrogate to detect reaction with hypochlorite.

Methyl salicylate (MeS) has a rich history as an inert physical simulant for the chemical warfare agents sulfur mustard and soman, where it is used extensively for liquid- and vapor-permeation testing. Here we demonstrate possible utility of MeS as a reactivity simulant for chlorine-based decontaminants. In these experiments MeS was reacted with sodium hypochlorite varying stoichiometry, temperature, reaction time, and pH. No colored oxidation products were observed; however, chlorination of the aromatic ring occurred ortho (methyl 3-chlorosalicylate) and para (methyl 5-chlorosalicylate) to the position bearing the -OH group in both the mono- and disubstituted forms. The monosubstituted para product accumulated initially, and the ortho and 3,5-dichloro products formed over the next several hours. Yields from reactions conducted below pH 11 declined rapidly with decreasing pH. Reactions run at 40 °C produced predominantly para substitution, while those run at 0 °C produced lower yields of ortho- and para-substituted products. Reactions were also carried out on textile substrates of cotton, 50/50 nylon-cotton, and a meta aramid. The textile data broadly reproduced reaction times and stoichiometry observed in the liquid phase, but are complicated by physical and possibly chemical interactions with the fabric. These data indicate that, for hypochlorite-containing neutralizing agents operating at strongly alkaline pH, one can expect MeS to react stoichiometrically with the hypochlorite it encounters. This suggests utility of MeS in lieu of such highly hazardous surrogates as monochloroalkyl sulfides as a simulant for threat scenarios involving the stoichiometric decomposition of sulfur mustard. Specifically, the extent of coverage of the simulant on a fabric by the neutralizing agent can be directly measured. Similar reactivity toward other halogen oxidizing agents is likely but remains to be demonstrated.

A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.

BACKGROUND: A major concern among health care experts is a projected shortage of N95 filtering facepiece respirators (FFRs) during an influenza pandemic. One option for mitigating an FFR shortage is to decontaminate and reuse the devices. Many parameters, including biocidal efficacy, filtration performance, pressure drop, fit, and residual toxicity, must be evaluated to verify the effectiveness of this strategy. The focus of this research effort was on evaluating the ability of microwave-generated steam, warm moist heat, and ultraviolet germicidal irradiation at 254 nm to decontaminate H1N1 influenza virus. METHODS: Six commercially available FFR models were contaminated with H1N1 influenza virus as aerosols or droplets that are representative of human respiratory secretions. A subset of the FFRs was treated with the aforementioned decontamination technologies, whereas the remaining FFRs were used to evaluate the H1N1 challenge applied to the devices. RESULTS: All 3 decontamination technologies provided >4-log reduction of viable H1N1 virus. In 93% of our experiments, the virus was reduced to levels below the limit of detection of the method used. CONCLUSIONS: These data are encouraging and may contribute to the evolution of effective strategies for the decontamination and reuse of FFRs.

Method for contamination of filtering facepiece respirators by deposition of MS2 viral aerosols.

A droplet/aerosol loading chamber was designed to deliver uniform droplets/aerosols onto substrates. An ultrasonic nebulizer was used to produce virus-containing droplets from artificial saliva to emulate those from coughing and sneezing. The operating conditions were determined by adjusting various parameters to achieve loading density and uniformity requirements. The count median diameter and mass median diameter were 0.5-2 and 3-4 µm, respectively, around the loading location when 35% relative humidity was applied. The average loading density was ∼2×103 plaque-forming units/cm2 for 5-min loading time with a virus titer of 107 plaque-forming units/mL. Six different filtering facepiece respirators from commercial sources were loaded to evaluate uniform distribution. For each of the six FFRs, the virus loading uniformity within a sample and across numerous samples was 19.21% and 12.20%, respectively. This system supports a standard method for loading viable bioaerosols onto specimen surfaces when different decontamination techniques are to be compared.

Field demonstration of visible opacity photographic systems.

The Digital Opacity Compliance System (DOCS) is an innovative method that uses digital imaging technology to quantify visible opacity of stationary sources. DOCS, which has been demonstrated at pilot and full scale as a technically defensible and economically attractive alternative to U.S. Environmental Protection Agency (EPA) Reference Method 9 (Method 9), uses commercial-off-the-shelf (COTS) digital cameras in combination with a user-friendly computer software package to determine opacity. To date, all DOCS field testing has been conducted using two models of digital cameras, notably, Kodak Models DC265 and DC290, both of which are no longer commercially available. To ensure that field-validated digital cameras will be available to future DOCS users, a suite of new digital cameras was evaluated with the opacity determination software including the following: (1) Sony Model Cybershot Model DSC-WI, (2) Nikon Model Coolpix 5200, (3) Fuji Finepix Model E500, and (4) Kodak Model DX6490. Within the opacity range of regulatory interest, that is, 0-40%, the Sony Cybershot Model DSC-WI and Nikon Coolpix Model 5200 digital cameras were found to generate plume photographs of which the DOCS opacity analysis yielded results that were statistically equivalent to the previously field-validated Kodak Model DC290. In contrast, the Fuji Finepix Model E500 generated plume photographs of which the DOCS opacity analysis were, on average, 2.2% less than those generated by the Kodak Model DC290 photographs, a difference that was determined to be statistically significant. Over the same opacity range, photographs taken by the Kodak Model DX6490 yielded DOCS opacity readings that were found to be statistically equivalent to a Method 9-certified transmissometer. Based on the results from the current digital camera validation testing approach, EPA has developed a new camera-based visible opacity measurement method titled "Determination of Visible Emission Opacity from Stationary Sources Using Computer-Based Photographic Analysis Systems." The proposed method is expected to be promulgated after closure of the public comment period.

Validation of the digital opacity compliance system under regulatory enforcement conditions.

U.S. Environmental Protection Agency (EPA) Emission Measurement Center in conjunction with EPA Regions VI and VIII, the state of Utah, and the U.S. Department of Defense have conducted a series of long-term pilot and field tests to determine the accuracy and reliability of a visible opacity monitoring system consisting of a conventional digital camera and a separate computer software application for plume opacity determination. This technology, known as the Digital Opacity Compliance System (DOCS), has been successfully demonstrated at EPA-sponsored Method-9 "smoke schools", as well as at a number of government and commercially operated industrial facilities. Results from the current DOCS regulatory pilot study demonstrated that, under regulatory enforcement conditions, the average difference in opacity measurement between the DOCS technology and EPA Reference Method 9 (Method 9) was 1.12%. This opacity difference, which was computed from the evaluation of 241 regulated air sources, was found to be statistically significant at the 99% confidence level. In evaluating only those sources for which a nonzero visible opacity level was recorded, the

Activated carbon fiber cloth electrothermal swing adsorption system.

Capture and recovery of hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) from gas streams using physical adsorption onto activated carbon fiber cloth (ACFC) is demonstrated on the bench-scale. This system is regenerated electrothermally, by passing an electric current directly through the ACFC. The adsorbate desorbs from the ACFC, rapidly condenses on the inside walls of the adsorber, and then drains from the adsorber as a pure liquid. Rapid electrothermal desorption exhibits such unique characteristics as extremely low purge gas flow rate, rapid rate of ACFC heating, rapid mass transfer kinetics inherent to ACFC, and in-vessel condensation. An existing system was scaled up 500%, and the new system was modeled using material and energy balances. Adsorption isotherms using methyl ethyl ketone (MEK) and ACFC were obtained while electricity passed through the ACFC and at temperatures above MEK's boiling point. These isotherms agreed within 7% to Dubinin-Radushkevich modeled isotherms that were extrapolated from independently determined gravimetric measurements obtained at lower temperatures. Energy and material balances for the electrothermal desorption of organic vapors and ACFC agree to within 7% of experimentally measured values. These results allow the modeling of electrothermal desorption of organic vapors from gas streams with in-vessel condensation to optimize operating conditions of the system during regeneration of the adsorbent.