Last data update: Jan 27, 2025. (Total: 48650 publications since 2009)
Records 1-21 (of 21 Records) |
Query Trace: Fisher EM[original query] |
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N95 filtering facepiece respirator reuse, extended use, and filtration efficiency
Wang RC , Addo N , Degesys NF , Fahimi J , Ford JS , Rosenthal E , Harris AR , Yaffee AQ , Peterson S , Rothmann RE , DeAngelis J , Tolia V , Shah MN , Stephenson TB , Nogueira-Prewitt SJ , Yoon KN , Fisher EM , Raven MC . JAMA Netw Open 2024 7 (10) e2441663 This cohort study examines the association of reuse of N95 filtering facepiece respirators and N95 filtration efficiency. | eng |
Development of an experimental technique to determine the barrier performance of medical gloves when stretched
Soo JC , Portnoff L , Bickson J , Fisher EM . Ann Work Expo Health 2024 Protective clothing standards, such as test methods published by ASTM International, play an integral role in ensuring the performance of personal protective equipment. The standard tests are not without limitations and are periodically reviewed and often updated. Some tests may not be reflective of in-use conditions. A new test cell was designed using sanitary fixtures to evaluate the effect of glove stretch on barrier performance using fluorescein solution as the challenge agent for enhanced visualization and fluorometer detection. Domed-shaped and flat screens were developed to permit and limit glove stretch within the test cell. The barrier performance of glove swatches was evaluated for both stretched and unstretched states. Latex, nitrile, and vinyl glove models of various thicknesses were evaluated. The tests were conducted following pressure and time parameters specified in ASTM F903, ASTM F1670, and ASTM F1671. Fluorescein solution movement, which may occur through penetration, was measured using a fluorometer. Glove stretch caused a reduction in glove thickness ranging from 16% to 40%. Overall, 21 sample failures were found (16.7%; n = 126) regardless of test condition. Nitrile gloves provided better barrier efficacy with the lowest failure rates (2.38%; 1 failure out of 42) compared to latex (19.4%; 7 failures out of 36) and vinyl gloves (27.1%; 13 failures out of 48). Differences in failure rates between stretched and unstretched gloves were insignificant; however, the latex material showed a 2.5 times increase in failures when stretched compared to unstretched. The new test apparatus was able to differentiate between the barrier performance of different glove materials. The use of a domed screen allowed the gloves to stretch, a condition that better represents the state of gloves when in use. Analysis of samples collected from the glove surface opposite to the exposure may provide a way to assess chemical permeation in addition to penetration. |
Viewpoint: Can qPCR replace the standard plaque assay in the ASTM F1671 to assess personal protective equipment barrier performance?
Di Giuseppe M , Fisher EM , Greenawald L , Pollard JP . Int J Cloth Sci Technol 2024 36 (3) 385-392 ![]() ![]() |
Assessment of glove stretch and storage temperature on fentanyl permeation: Implications for standard test methods and PPE recommendations
Fisher EM , Streeter RT , Hofacre KC , Greenawald LA , Yoon NK , Soo JC , Keyes PH . J Occup Environ Hyg 2024 1-10 The National Institute for Occupational Safety and Health recommends the use of nitrile gloves with a minimum thickness of 5.0 ± 2.0 mil [0.127 ± 0.051 millimeters] in situations where it is suspected or known that fentanyl or other illicit drugs are present. However, there is limited data available on fentanyl permeation through gloves. Current test methods used to measure fentanyl permeation do not consider the effect of glove fit and flexion. Furthermore, first responders need to have PPE readily available in the field, and storage conditions may affect the protective performance of the gloves. The objective of this study was to evaluate the effects of glove stretch and storage temperatures on glove durability and barrier performance against fentanyl. Nine nitrile glove models previously shown to be resistant to fentanyl permeation were selected for this investigation. These nine models were stretched 25% in one linear direction, to consider glove fit and flexion, and tested against fentanyl hydrochloride permeation. Additionally, four of the nine glove models were stored at 48 °C, 22 °C, and -20 °C, and evaluated for tensile strength, ultimate elongation, and puncture resistance after up to 16 wk of storage and fentanyl permeation after up to 8 wk of storage. At least one sample for six of the nine tested models had maximum permeation over the test method fail threshold when stretched. The tested storage temperatures showed no effect on glove tensile strength, ultimate elongation, and puncture resistance. The findings of this study can be used to inform PPE recommendations, with consideration to storage practices and proper sizing for first responders with potential exposure to fentanyl and other illicit drugs. The results of this study can be used to assess the need for new standard test methods to evaluate the barrier performance of gloves and shelf-life determination with consideration to glove fit. |
Persistence of SARS-Co-V-2 on N95 filtering facepiece respirators: implications for reuse.
Fisher EM , Kuhlman MR , Choi YW , Jordan TL , Sunderman M . J Occup Environ Hyg 2021 18 (12) 1-11 In response to the shortage of N95 filtering facepiece respirators for healthcare workers during the COVID-19 pandemic, the Centers for Disease Control and Prevention issued guidance for extended use and limited reuse of N95 FFRs to conserve supply. Previously worn N95 filtering facepiece respirators can serve as a source of pathogens, which can be transferred to the wearer while doffing and donning a respirator when practicing reuse. When practicing limited filtering facepiece respirators reuse, to reduce the risk of self-contamination, the Centers for Disease Control and Prevention recommends storing filtering facepiece respirators for five days between uses to allow for the decay of viable pathogens including SARS-CoV-2. This study assesses the persistence of the SARS-CoV-2 strain USA-WA1/2020 on N95 filtering facepiece respirators under controlled storage conditions for up to five days to inform the Centers for Disease Control and Prevention guidance. Coupons excised from six N95 filtering facepiece respirator models and glass slide coverslips were inoculated with the virus in a defined culture medium and in human saliva and stored at 20 °C and 20%, 45%, and 75% relative humidity. Statistically significant differences in SARS-CoV-2 half-lives were measured among the tested humidity levels with half-lives decreasing from an average of approximately 30 hours at 20% relative humidity to approximately 2 hours at 75% relative humidity. Significant differences in virus half-lives were also observed between the culture medium and saliva suspension media at 20% and 45% relative humidity with half lives up to 2.9 times greater when the virus was suspended in cell culture medium. The five-day storage strategy, assessed in this study, resulted in a minimum of 93.4% reduction in viable virus for the most challenging condition (20% relative humidity, cell culture medium) and exceeding 99% reduction in virus at all other conditions. |
A Review of Decontamination Methods for Filtering Facepiece Respirators.
Bergman M , Fisher EM , Heimbuch BK . J Int Soc Respir Prot 2020 37 (2) 71-86 During the current COVID-19 infectious disease pandemic, the demand for NIOSH-approved filtering facepiece respirators (FFR) has exceeded supplies and decontamination and reuse of FFRs has been implemented by various user groups. FFR decontamination and reuse is only intended to be implemented as a crisis capacity strategy. This paper provides a review of decontamination procedures in the published literature and calls attention to their benefits and limitations. In most cases, the data are limited to a few FFR models and a limited number of decontamination cycles. Institutions planning to implement a decontamination method must understand its limitations in terms of the degree of inactivation of the intended mircroorganisms and the treatment's effects on the fit and filtration of the device. A supplement to this publication is available https://www.isrp.com/the-isrp-journal/journal- public-abstracts/1215-vol-37-no-2-2020-supplementary-material |
COVID-19 and the Workplace: Research Questions for the Aerosol Science Community.
Lindsley WG , Blachere FM , Burton NC , Christensen B , Estill CF , Fisher EM , Martin SB , Mead KR , Noti JD , Seaton M . Aerosol Sci Technol 2020 54 (10) 1117-1123 The global Coronavirus Disease (COVID-19) pandemic caused by the SARS-CoV-2 virus has raised many urgent questions about the transmission of this disease, including the possible roles of aerosols containing SARS-CoV-2. This is particularly true in workplace settings where workers may encounter customers and coworkers who are infected with COVID-19 and where aerosols can be produced in a variety of ways. Research by the aerosol science community is needed to learn more about whether SARS-CoV-2 can spread by infectious aerosols and about the effectiveness of different protective measures. The purpose of this commentary is to present some of the questions surrounding aerosols containing SARS-CoV-2 and to provide suggestions for future research topics. |
Fentanyl and carfentanil permeation through commercial disposable gloves
Greenawald LA , Hofacre KC , Fisher EM . J Occup Environ Hyg 2020 17 (9) 1-10 In 2018, the Centers for Disease Control and Prevention reported that opioid overdose deaths (including fentanyl and carfentanil) comprised 46,802 (69%) of the 67,367 total drug overdose deaths. The opioid overdose epidemic affects Americans not only at home but also in the workplace. First responders may be at risk of opioid exposure during incidents such as vehicle searches and responses to overdose calls. To reduce direct exposure to opioids and other hazardous drugs, first responders rely in part on personal protective equipment (PPE) as their last line of defense. First responders seek guidance from the National Institute for Occupational Safety and Health (NIOSH) regarding appropriate PPE selection for potential opioid exposure. There is limited empirical glove performance data for illicit drugs. Empirical data are needed to validate NIOSH's current recommendations regarding gloves to help prevent exposure to illicit drugs (i.e., powder-free nitrile gloves with a minimum thickness of 5 +/- 2 mil [0.127 +/- 0.051 millimeters]); however, no industry standard or test method currently exists for specifically evaluating PPE performance against fentanyl and its analogs. To understand the permeation qualities of gloves when challenged against fentanyl and carfentanil solutions, the ASTM International (formerly American Society for Testing and Materials) ASTM D6978-19 standard for chemotherapy drug glove permeation was adapted to test fentanyl and carfentanil hydrochloride solution permeation through twelve disposable glove models, including five models in which the manufacturers claim fentanyl protection. No nitrile glove models showed fentanyl or carfentanil permeation rates above the chemotherapy drug threshold criterion of 0.01 microg/cm(2)/min (i.e., thereby meeting the performance requirement) as calculated using the ASTM D6978-19 standard within the 240-min test. Latex and vinyl glove materials exhibited fentanyl and carfentanil permeation with permeation rates above this threshold. These findings are among the first empirical data to support NIOSH's current opioid glove recommendations and define procedures that could be used to support industry standards for evaluating opioid permeation through air-impermeable PPE materials. |
Planning for epidemics and pandemics: assessing the potential impact of extended use and reuse strategies on respirator usage rates to support supply-and-demand planning efforts
Yorio PL , Fisher EM , Kilinc-Balci FS , Rottach D , Harney J , Seaton M , Dahm MM , Niemeier T . J Int Soc Respir Prot 2020 37 (1) 52-60 During epidemics and pandemics healthcare personnel (HCP) are on the front line of disease containment and mitigation. Personal protective equipment (PPE), such as NIOSH-approved N95 filtering facepiece respirators (FFRs), serve an important role in minimizing HCP risks and are in high demand during public health emergencies. Because PPE demand can exceed supply, various public health strategies have been developed to reduce the rate of PPE consumption as supply dwindles. Extended use and limited reuse of N95 FFRs are strategies advocated by many governmental agencies used to increase the number of times a device can be used. Increased use of respirators designed for reuse-such as powered air-purifying respirators (PAPRs) and elastomeric half-mask and full facepiece air-purifying respirators- is another option designed to reduce the continuous need for new devices as the daily need for respirator use increases. Together, these strategies are designed to reduce the number of PPE units that must be discarded daily and, therefore, extend the longevity of available supply. The purpose of this paper is to theoretically estimate the impact of extended use and limited reuse strategies for N95 FFRs and the increased use of reusable respirator options on PPE consumed. The results suggest that a considerable reduction in PPE consumption would result from extended use and limited reuse of N95 FFRs and the increased use of respirators designed for reuse; however, the practical benefits must be balanced with the risks and economic costs. In addition, extended use and reuse strategies must be accompanied by proper procedures to reduce risk. The study is designed to support epidemic and pandemic PPE supply and demand planning efforts. |
A control banding framework for protecting the US workforce from aerosol transmissible infectious disease outbreaks with high public health consequences
Sietsema M , Radonovich L , Hearl FJ , Fisher EM , Brosseau LM , Shaffer RE , Koonin LM . Health Secur 2019 17 (2) 124-132 Recent high-profile infectious disease outbreaks illustrate the importance of selecting appropriate control measures to protect a wider range of employees, other than those in healthcare settings. In such settings, where routine exposure risks are often high, control measures may be more available, routinely implemented, and studied for effectiveness. In the absence of evidence-based guidelines or established best practices for selecting appropriate control measures, employers may unduly rely on personal protective equipment (PPE) because of its wide availability and pervasiveness as a control measure, circumventing other effective options for protection. Control banding is one approach that may be used to assign job tasks into risk categories and prioritize the application of controls. This article proposes an initial control banding framework for workers at all levels of risk and incorporates a range of control options, including PPE. Using the National Institutes of Health (NIH) risk groups as a surrogate for toxicity and combining the exposure duration with the exposure likelihood, we can generate the risk of a job task to the worker. |
Healthcare personnel exposure in an emergency department during influenza season
Rule AM , Apau O , Ahrenholz SH , Brueck SE , Lindsley WG , de Perio MA , Noti JD , Shaffer RE , Rothman R , Grigorovitch A , Noorbakhsh B , Beezhold DH , Yorio PL , Perl TM , Fisher EM . PLoS One 2018 13 (8) e0203223 INTRODUCTION: Healthcare personnel are at high risk for exposure to influenza by direct and indirect contact, droplets and aerosols, and by aerosol generating procedures. Information on air and surface influenza contamination is needed to assist in developing guidance for proper prevention and control strategies. To understand the vulnerabilities of healthcare personnel, we measured influenza in the breathing zone of healthcare personnel, in air and on surfaces within a healthcare setting, and on filtering facepiece respirators worn by healthcare personnel when conducting patient care. METHODS: Thirty participants were recruited from an adult emergency department during the 2015 influenza season. Participants wore personal bioaerosol samplers for six hours of their work shift, submitted used filtering facepiece respirators and medical masks and completed questionnaires to assess frequency and types of interactions with potentially infected patients. Room air samples were collected using bioaerosol samplers, and surface swabs were collected from high-contact surfaces within the adult emergency department. Personal and room bioaerosol samples, surface swabs, and filtering facepiece respirators were analyzed for influenza A by polymerase chain reaction. RESULTS: Influenza was identified in 42% (53/125) of personal bioaerosol samples, 43% (28/ 96) of room bioaerosol samples, 76% (23/30) of pooled surface samples, and 25% (3/12) of the filtering facepiece respirators analyzed. Influenza copy numbers were greater in personal bioaerosol samples (17 to 631 copies) compared to room bioaerosol samples (16 to 323 copies). Regression analysis suggested that the amount of influenza in personal samples was approximately 2.3 times the amount in room samples (Wald chi2 = 16.21, p<0.001). CONCLUSIONS: Healthcare personnel may encounter increased concentrations of influenza virus when in close proximity to patients. Occupations that require contact with patients are at an increased risk for influenza exposure, which may occur throughout the influenza season. Filtering facepiece respirators may become contaminated with influenza when used during patient care. |
Assessment of environmental and surgical mask contamination at a student health center - 2012-2013 influenza season
Ahrenholz SH , Brueck SE , Rule AM , Noti JD , Noorbakhs B , Blachere FM , de Perio MA , Lindsley WG , Shaffer RE , Fisher EM . J Occup Environ Hyg 2018 15 (9) 1-30 Increased understanding of influenza transmission is critical for pandemic planning and selecting appropriate controls for healthcare personnel safety and health. The goals of this pilot study were to assess environmental contamination in different areas and at two time periods in the influenza season and to determine the feasibility of using surgical mask contamination to evaluate potential exposure to influenza virus. Bioaerosol samples were collected over 12 days (two 6-day sessions) at 12 locations within a student health center using portable two-stage bioaerosol samplers operating 8 hours each day. Surface samples were collected each morning and afternoon from common high-contact non-porous hard surfaces from rooms and locations where bioaerosol samplers were located. Surgical masks worn by participants while in contact with patients with influenza-like illness were collected. A questionnaire administered to each of the 12 participants at the end of each workday and another at the end of each workweek assessed influenza-like illness symptoms, estimated the number of influenza-like illness patient contacts, hand hygiene, and surgical mask usage. All samples were analyzed using qPCR. Over the 12 days of the study, three of the 127 (2.4%) bioaerosol samples, two of 483 (0.41%) surface samples, and zero of 54 surgical masks were positive for influenza virus. For the duration of contact that occurred with an influenza patient on any of the 12 days, nurse practitioners and physicians reported contacts with influenza-like illness patients > 60 minutes, medical assistants reported 15-44 minutes, and administrative staff reported < 30 minutes. Given the limited number of bioaerosol and surface samples positive for influenza virus in the bioaerosol and surface samples, the absence of influenza virus on the surgical masks provides inconclusive evidence for the potential to use surgical masks to assess exposure to influenza viruses. Further studies are needed to determine feasibility of this approach in assessing healthcare personnel exposures. Information learned in this study can inform future field studies on influenza transmission. |
Assessment of influenza virus exposure and recovery from contaminated surgical masks and N95 respirators
Blachere FM , Lindsley WG , McMillen CM , Beezhold DH , Fisher EM , Shaffer RE , Noti JD . J Virol Methods 2018 260 98-106 Healthcare workers (HCWs) are at significantly higher risk of exposure to influenza virus during seasonal epidemics and global pandemics. During the 2009 influenza pandemic, some healthcare organizations recommended that HCWs wear respiratory protection such as filtering facepiece respirators, while others indicated that facemasks such as surgical masks (SMs) were sufficient. To assess the level of exposure a HCW may possibly encounter, the aim of this study was to (1.) evaluate if SMs and N95 respirators can serve as "personal bioaerosol samplers" for influenza virus and (2.) determine if SMs and N95 respirators contaminated by influenza laden aerosols can serve as a source of infectious virus for indirect contact transmission. This effort is part of a National Institute for Occupational Safety and Health 5-year multidisciplinary study to determine the routes of influenza transmission in healthcare settings. A coughing simulator was programmed to cough aerosol particles containing influenza virus over a wide concentration range into an aerosol exposure simulation chamber virus/L of exam room air), and a breathing simulator was used to collect virus on either a SM or N95 respirator. Extraction buffers containing nonionic and anionic detergents as well as various protein additives were used to recover influenza virus from the masks and respirators. The inclusion of 0.1% SDS resulted in maximal influenza RNA recovery (41.3%) but with a complete loss of infectivity whereas inclusion of 0.1% bovine serum albumin resulted in reduced RNA recovery (6.8%) but maximal retention of virus infectivity (17.9%). Our results show that a HCW's potential exposure to airborne influenza virus can be assessed in part through analysis of their SMs and N95 respirators, which can effectively serve as personal bioaerosol samplers. |
Transfer of bacteriophage MS2 and fluorescein from N95 filtering facepiece respirators to hands: Measuring fomite potential
Brady TM , Strauch AL , Almaguer CM , Niezgoda G , Shaffer RE , Yorio PL , Fisher EM . J Occup Environ Hyg 2017 14 (11) 0 Contact transmission of pathogens from personal protective equipment is a concern within the healthcare industry. During public health emergency outbreaks, resources become constrained and the reuse of personal protective equipment, such as N95 filtering facepiece respirators, may be needed. This study was designed to characterize the transfer of bacteriophage MS2 and fluorescein between filtering facepiece respirators and the wearer's hands during three simulated use scenarios. Filtering facepiece respirators were contaminated with MS2 and fluorescein in droplets or droplet nuclei. Thirteen test subjects performed filtering facepiece respirator use scenarios including improper doffing, proper doffing and reuse, and improper doffing and reuse. Fluorescein and MS2 contamination transfer were quantified. The average MS2 transfer from filtering facepiece respirators to the subjects' hands ranged from 7.6-15.4% and 2.2-2.7% for droplet and droplet nuclei derived contamination, respectively. Handling filtering facepiece respirators contaminated with droplets resulted in higher levels of MS2 transfer compared to droplet nuclei for all use scenarios (p = 0.007). MS2 transfer from droplet contaminated filtering facepiece respirators during improper doffing and reuse was greater than transfer during improper doffing (p = 0.008) and proper doffing and reuse (p = 0.042). Droplet contamination resulted in higher levels of fluorescein transfer compared to droplet nuclei contaminated filtering facepiece respirators for all use scenarios (p = 0.009). Fluorescein transfer was greater for improper doffing and reuse (p = 0.007) from droplet contaminated masks compared to droplet nuclei contaminated filtering facepiece respirators and for improper doffing and reuse when compared improper doffing (p = 0.017) and proper doffing and reuse (p = 0.018) for droplet contaminated filtering facepiece respirators. For droplet nuclei contaminated filtering facepiece respirators, the difference in MS2 and fluorescein transfer did not reach statistical significance when comparing any of the use scenarios. The findings suggest that the results of fluorescein and MS2 transfer were consistent and highly correlated across the conditions of study. The data supports CDC recommendations for using proper doffing techniques and discarding filtering facepiece respirators that are directly contaminated with secretions from a cough or sneeze. |
Assessing the Efficacy of Tabs on Filtering Facepiece Respirator Straps to Increase Proper Doffing Techniques While Reducing Contact Transmission of Pathogens
Strauch AL , Brady TM , Niezgoda G , Almaguer CM , Shaffer RE , Fisher EM . J Occup Environ Hyg 2016 13 (10) 794-801 NIOSH-certified N95 filtering facepiece respirators (FFRs) are used in healthcare settings as a control measure to mitigate exposures to airborne infectious particles. When the outer surface of an FFR becomes contaminated, it presents a contact transmission risk to the wearer. The Centers for Disease Control and Prevention (CDC) guidance recommends that healthcare workers (HCWs) doff FFRs by grasping the straps at the back of the head to avoid contact with the potentially contaminated surface. Adherence to proper doffing technique is reportedly low due to numerous factors including difficulty in locating and grasping the straps. This study compares the impact of tabs placed on FFR straps to controls (without tabs) on proper doffing, ease of use and comfort, and reduction of transfer of contamination to the wearer. Utilizing a fluorescent agent as a tracer to track contamination from FFRs to hand and head areas of 20 human subjects demonstrated that there was no difference in tabbed FFR straps and controls with respect to promoting proper doffing (p = 0.48), but did make doffing easier (p = 0.04) as indicated by 7 of 8 subjects that used the tabs. Seven of the 20 subjects felt that FFRs with tabs were easier to remove, while only 2 of 20 indicated that FFRs without tabs were easier to remove. Discomfort was not a factor for either FFR strap type. When removing an FFR with contaminated hands, the use of the tabs significantly reduced the amount of tracer transfer compared to straps without tabs (p = 0.012). FFRs with tabs on the straps are associated with ease of doffing and significantly less transfer of the fluorescent tracer. |
MS2 Coliphage as a Surrogate for 2009 Pandemic Influenza A (H1N1) Virus (pH1N1) in Surface Survival Studies on N95 Filtering Facepiece Respirators
Coulliette AD , Perry KA , Fisher EM , Edwards JR , Shaffer RE , Noble-Wang J . J Int Soc Respir Prot 2014 21 (1) 14-22 Research on influenza viruses regarding transmission and survival has surged in the recent years due to infectious emerging strains and outbreaks such as the 2009 Influenza A (H1N1) pandemic. MS2 coliphage has been applied as a surrogate for pathogenic respiratory viruses, such as influenza, as it's safe for personnel to handle and requires less time and labor to measure virus infectivity. However, direct comparisons to determine the effectiveness of coliphage as a surrogate for influenza virus regarding droplet persistence on personal protective equipment such as N95 filtering facepiece respirators (FFRs) are lacking. Persistence of viral droplets deposited on FFRs in healthcare settings is important to discern due to the potential risk of infection via indirect fomite transmission. The objective of this study was to determine if MS2 coliphage could be applied as a surrogate for influenza A viruses for studying persistence when applied to the FFRs as a droplet. The persistence of MS2 coliphage and 2009 Pandemic Influenza A (H1N1) Virus on FFR coupons in different matrices (viral media, 2% fetal bovine serum, and 5 mg ml(-1) mucin) were compared over time (4, 12, 24, 48, 72, and 144 hours) in typical absolute humidity conditions (4.1 × 10(5) mPa [18°C/20% relative humidity (RH)]). Data revealed significant differences in viral infectivity over the 6-day period (H1N1- P <0.0001; MS2 - P <0.005), although a significant correlation of viral log(10) reduction in 2% FBS (P <0.01) was illustrated. Overall, MS2 coliphage was not determined to be a sufficient surrogate for influenza A virus with respect to droplet persistence when applied to the N95 FFR as a droplet. |
Considerations for recommending extended use and limited reuse of filtering facepiece respirators in healthcare settings
Fisher EM , Shaffer RE . J Occup Environ Hyg 2014 11 (8) D115-28 Public health organizations, such as the Centers for Disease Control and Prevention (CDC), are increasingly recommending the use of N95 filtering facepiece respirators (FFRs) in healthcare settings. For infection control purposes, the usual practice is to discard FFRs after close contact with a patient ("single use"). However, in some situations, such as during contact with tuberculosis patients, limited FFR reuse (i.e., repeated donning and doffing of the same FFR by the same person) is practiced. A related practice, extended use, involves wearing the same FFR for multiple patient encounters without doffing. Extended use and limited FFR reuse have been recommended during infectious disease outbreaks and pandemics to conserve FFR supplies. This commentary examines CDC recommendations related to FFR extended use and limited reuse and analyzes available data from the literature to provide a relative estimate of the risks of these practices compared to single use. |
Validation and application of models to predict facemask influenza contamination in healthcare settings
Fisher EM , Noti JD , Lindsley WG , Blachere FM , Shaffer RE . Risk Anal 2014 34 (8) 1423-34 Facemasks are part of the hierarchy of interventions used to reduce the transmission of respiratory pathogens by providing a barrier. Two types of facemasks used by healthcare workers are N95 filtering facepiece respirators (FFRs) and surgical masks (SMs). These can become contaminated with respiratory pathogens during use, thus serving as potential sources for transmission. However, because of the lack of field studies, the hazard associated with pathogen-exposed facemasks is unknown. A mathematical model was used to calculate the potential influenza contamination of facemasks from aerosol sources in various exposure scenarios. The aerosol model was validated with data from previous laboratory studies using facemasks mounted on headforms in a simulated healthcare room. The model was then used to estimate facemask contamination levels in three scenarios generated with input parameters from the literature. A second model estimated facemask contamination from a cough. It was determined that contamination levels from a single cough ( approximately 19 viruses) were much less than likely levels from aerosols (4,473 viruses on FFRs and 3,476 viruses on SMs). For aerosol contamination, a range of input values from the literature resulted in wide variation in estimated facemask contamination levels (13-202,549 viruses), depending on the values selected. Overall, these models and estimates for facemask contamination levels can be used to inform infection control practice and research related to the development of better facemasks, to characterize airborne contamination levels, and to assist in assessment of risk from reaerosolization and fomite transfer because of handling and reuse of contaminated facemasks. |
Reaerosolization of MS2 bacteriophage from an N95 filtering facepiece respirator by simulated coughing
Fisher EM , Richardson AW , Harpest SD , Hofacre KC , Shaffer RE . Ann Occup Hyg 2011 56 (3) 315-25 The supply of N95 filtering facepiece respirators (FFRs) may not be adequate to match demand during a pandemic outbreak. One possible strategy to maintain supplies in healthcare settings is to extend FFR use for multiple patient encounters; however, contaminated FFRs may serve as a source for the airborne transmission of virus particles. In this study, reaerosolization of virus particles from contaminated FFRs was examined using bacteriophage MS2 as a surrogate for airborne pathogenic viruses. MS2 was applied to FFRs as droplets or droplet nuclei. A simulated cough (370 l min(-1) peak flow) provided reverse airflow through the contaminated FFR. The number and size of the reaerosolized particles were measured using gelatin filters and an Andersen Cascade Impactor (ACI). Two droplet nuclei challenges produced higher percentages of reaerosolized particles (0.21 and 0.08%) than a droplet challenge (<0.0001%). Overall, the ACI-determined size distribution of the reaerosolized particles was larger than the characterized loading virus aerosol. This study demonstrates that only a small percentage of viable MS2 viruses was reaerosolized from FFRs by reverse airflow under the conditions evaluated, suggesting that the risks of exposure due to reaerosolization associated with extended use can be considered negligible for most respiratory viruses. However, risk assessments should be updated as new viruses emerge and better workplace exposure data becomes available. |
Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators
Fisher EM , Williams JL , Shaffer RE . PLoS One 2011 6 (4) e18585 Reusing filtering facepiece respirators (FFRs) has been suggested as a strategy to conserve available supplies for home and healthcare environments during an influenza pandemic. For reuse to be possible, used FFRs must be decontaminated before redonning to reduce the risk of virus transmission; however, there are no approved methods for FFR decontamination. An effective method must reduce the microbial threat, maintain the function of the FFR, and present no residual chemical hazard. The method should be readily available, inexpensive and easily implemented by healthcare workers and the general public. Many of the general decontamination protocols used in healthcare and home settings are unable to address all of the desired qualities of an efficient FFR decontamination protocol. The goal of this study is to evaluate the use of two commercially available steam bags, marketed to the public for disinfecting infant feeding equipment, for FFR decontamination. The FFRs were decontaminated with microwave generated steam following the manufacturers' instructions then evaluated for water absorption and filtration efficiency for up to three steam exposures. Water absorption of the FFR was found to be model specific as FFRs constructed with hydrophilic materials absorbed more water. The steam had little effect on FFR performance as filtration efficiency of the treated FFRs remained above 95%. The decontamination efficacy of the steam bag was assessed using bacteriophage MS2 as a surrogate for a pathogenic virus. The tested steam bags were found to be 99.9% effective for inactivating MS2 on FFRs; however, more research is required to determine the effectiveness against respiratory pathogens. |
A method to determine the available UV-C dose for the decontamination of filtering facepiece respirators
Fisher EM , Shaffer RE . J Appl Microbiol 2010 110 (1) 287-95 AIMS: To develop a method to assess model-specific parameters for ultraviolet-C (UV-C, 254 nm) decontamination of filtering facepiece respirators (FFRs). METHODS & RESULTS: UV-C transmittance was quantified for the distinct composite layers of six N95 FFR models and used to calculate model-specific alpha-values, the percentage of the surface UV-C irradiance available for the internal filtering medium (IFM). Circular coupons, excised from the FFRs, were exposed to aerosolized particles containing MS2 coliphage and treated with IFM-specific UV-C doses ranging from 38 to 4707 J m(-2) . Models exposed to a minimum IFM dose of 1000 J m(-2) demonstrated at least a 3 log reduction (LR) in viable MS2. Model-specific exposure times to achieve this IFM dose ranged from 2 to 266 min. CONCLUSIONS: UV-C transmits into and through FFR materials. LR of MS2 was a function of model-specific IFM UV-C doses. SIGNIFICANCE AND IMPACT OF THE STUDY: Filtering facepiece respirators are in high demand during infectious disease outbreaks, potentially leading to supply shortages. Reuse of disposable FFRs after decontamination has been discussed as a possible remediation strategy, but to date lacks supporting scientific evidence. The methods described here can be used to assess the likelihood that UV-C decontamination will be successful for specific FFR models. |
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