Face mask fit modifications that improve source control performance.

BACKGROUND: During the COVID-19 pandemic, face masks are used as source control devices to reduce the expulsion of respiratory aerosols from infected people. Modifications such as mask braces, earloop straps, knotting and tucking, and double masking have been proposed to improve mask fit however the data on source control are limited. METHODS: The effectiveness of mask fit modifications was determined by conducting fit tests on human subjects and simulator manikins and by performing simulated coughs and exhalations using a source control measurement system. RESULTS: Medical masks without modification blocked ≥56% of cough aerosols and ≥42% of exhaled aerosols. Modifying fit by crossing the earloops or placing a bracket under the mask did not increase performance, while using earloop toggles, an earloop strap, and knotting and tucking the mask increased performance. The most effective modifications for improving source control performance were double masking and using a mask brace. Placing a cloth mask over a medical mask blocked ≥85% of cough aerosols and ≥91% of exhaled aerosols. Placing a brace over a medical mask blocked ≥95% of cough aerosols and ≥99% of exhaled aerosols. CONCLUSIONS: Fit modifications can greatly improve the performance of face masks as source control devices for respiratory aerosols.

Evaluation of total inward leakage for NIOSH-approved elastomeric half-facepiece, full-facepiece, and powered air-purifying respirators using sodium chloride and corn oil aerosols.

Recently, total inward leakage (TIL) for filtering facepiece and elastomeric half-mask respirators (EHRs) was measured according to the International Organization for Standardization (ISO) test method standard 16900-1:2014 that showed larger TIL for corn oil aerosol than for NaCl aerosol. Comparison of TIL measured for different aerosols for higher protection level respirators is lacking. The objective of this study was to determine TIL for EHRs, full-facepiece respirators, and loose-fitting and tight-fitting powered air-purifying respirators (PAPRs) using NaCl and corn oil aerosols to compare. TIL was measured for two models each of EHRs, full-facepiece respirators, and loose-fitting and tight-fitting PAPRs. After fit testing with a PortaCount (TSI, St. Paul, MN) using the Occupational Safety and Health Administration (OSHA) protocol, eight subjects were tested in the NaCl aerosol chamber first and then in the corn oil aerosol chamber, while another eight subjects tested in the reverse order. Subjects were randomly assigned to one of the two groups. TIL was measured as a ratio of mass-based aerosol concentrations inside the mask to the test chamber while the subjects performed ISO 16900-1-defined exercises using continuous sampling methods. The concentration of corn oil aerosol was measured with one light scattering photometer, alternately, and NaCl aerosol was measured using two flame photometers. Results showed the geometric mean TIL for EHR was significantly (p < 0.05) larger for corn oil aerosol than for NaCl aerosol. EHR models equipped with P100 filters showed relatively smaller TIL values than the same models with N95 filters showing that TIL was inversely related to filter efficiency. Interestingly, TIL was significantly (p < 0.05) larger for NaCl aerosol than for corn oil aerosol for PAPRs, but not for full-facepiece respirators. TIL was inversely related to fit factors of respirator types. Overall, filter efficiency and faceseal leakage determine TIL. The relative trends in TIL for the two aerosols' test methods differ between respirator types indicating that generalization of TIL for respirator types may not be appropriate when using different test agents.

A comparison of performance metrics for cloth face masks as source control devices for simulated cough and exhalation aerosols.

Universal mask wearing is recommended by the Centers for Disease Control and Prevention to help control the spread of COVID-19. Masks reduce the expulsion of respiratory aerosols (called source control) and offer some protection to the wearer. However, masks vary greatly in their designs and construction materials, and it is not clear which are most effective. Our study tested 15 reusable cloth masks (which included face masks, neck gaiters, and bandanas), two medical masks, and two N95 filtering facepiece respirators as source control devices for aerosols ≤ 7 µm produced during simulated coughing and exhalation. These measurements were compared with the mask filtration efficiencies, airflow resistances, and fit factors. The source control collection efficiencies for the cloth masks ranged from 17% to 71% for coughing and 35% to 66% for exhalation. The filtration efficiencies of the cloth masks ranged from 1.4% to 98%, while the fit factors were 1.3 to 7.4 on an elastomeric manikin headform and 1.0 to 4.0 on human test subjects. The correlation coefficients between the source control efficacies and the other performance metrics ranged from 0.31 to 0.66 and were significant in all but one case. However, none of the alternative metrics were strong predictors of the source control performance of cloth masks. Our results suggest that a better understanding of the relationships between source control performance and metrics like filtration efficiency, airflow resistance, and fit factor are needed to develop simple methods to estimate the effectiveness of masks as source control devices for respiratory aerosols.

A comparison of performance metrics for cloth masks as source control devices for simulated cough and exhalation aerosols.

Universal mask wearing is recommended to help control the spread of COVID-19. Masks reduce the expulsion of aerosols of respiratory fluids into the environment (called source control) and offer some protection to the wearer. Masks are often characterized using filtration efficiency, airflow resistance, and manikin or human fit factors, which are standard metrics used for personal protective devices. However, none of these metrics are direct measurements of how effectively a mask blocks coughed and exhaled aerosols. We studied the source control performance of 15 cloth masks (face masks, neck gaiters, and bandanas), two medical masks, and two N95 filtering facepiece respirators by measuring their ability to block aerosols ≤ 7 µm expelled during simulated coughing and exhalation (called source control collection efficiency). These measurements were compared with filtration efficiencies, airflow resistances, and fit factors measured on manikin headforms and humans. Collection efficiencies for the cloth masks ranged from 17% to 71% for coughing and 35% to 66% for exhalation. Filtration efficiencies for the cloth masks ranged from 1.4% to 98%, while the fit factors were 1.3 to 7.4 on headforms and 1.0 to 4.0 on human subjects. The Spearman's rank correlation coefficients between the source control collection efficiencies and the standard metrics ranged from 0.03 to 0.68 and were significant in all but two cases. However, none of the standard metrics were strongly correlated with source control performance. A better understanding of the relationships between source control collection efficiency, filtration efficiency, airflow resistance, and fit factor is needed.

Whole-Genome Sequence of an Orf Virus Isolate Derived from a Cell Culture Infected with Contagious Ecthyma Vaccine.

This is a draft genome of an orf virus (ORFV) vaccine strain assembled via long- and short-read hybrid assembly. ORFV is a zoonotic pathogen that affects sheep and goats. The genome of the virus contained in the vaccine was found to have high similarity (98%) to those of other published strains.

Assessment of respirator fit capability test criteria for full-facepiece air-purifying respirators.

An ASTM International subcommittee on Respiratory Protection, F23.65 is currently developing a consensus standard for assessing respirator fit capability (RFC) criteria of half-facepiece air-purifying particulate respirators. The objective of this study was to evaluate if the test methods being developed for half-facepiece respirators can reasonably be applied to nonpowered full-facepiece-air-purifying respirators (FF-APR). Benchmark RFC test data were collected for three families of FF-APRs (a one-size-only family, a two-size family, and a three-size family). All respirators were equipped with P100 class particulate filters. Respirators were outfitted with a sampling probe to collect an in-mask particle concentration sample in the breathing zone of the wearer. Each of the six respirator facepieces was tested on the National Institute for Occupational Safety and Health 25-subject Bivariate Panel. The RFC test assessed face seal leakage using a PortaCount fit test. Subjects followed the corresponding Occupational Safety and Health Administration-accepted fit test protocol. Two donnings per subject/respirator model combination were performed. The panel passing rate (PPR) (number or percentage of subjects in the panel achieving acceptable fit on at least one of two donnings) was determined for each respirator family at specified fit factor passing levels of 500, 1,000, and 2,000. As a reasonable expectation based on a previous analysis of alpha and beta fit test errors for various panel sizes, the selected PPR benchmark for our study was >75%. At the fit factor passing level of 500 obtained on at least one of two donnings, the PPRs for three-, two-, and one-size families were 100, 79, and 88%, respectively. As the fit factor passing criterion increased from 500 to 1,000 or 2,000, PPRs followed a decreasing trend. Each of the three tested families of FF-APRs are capable of fitting ≥75% of the intended user population at the 500 fit factor passing level obtained on at least one of two donnings. The methods presented here can be used as a reference for standards development organizations considering developing RFC test requirements.

Occupational injuries in Ohio wood product manufacturing: a descriptive analysis with emphasis on saw-related injuries and associated causes.

BACKGROUND: Stationary sawing machinery is often a basic tool in the wood product manufacturing industry and was the source for over 2,500 injury/illness events that resulted in days away from work in 2010. METHODS: We examined 9 years of workers' compensation claims for the state of Ohio in wood product manufacturing with specific attention to saw-related claims. For the study period, 8,547 claims were evaluated; from this group, 716 saw-related cases were examined. RESULTS: The sawmills and wood preservation sub-sector experienced a 71% reduction in average incidence rate and an 87% reduction in average lost-time incidence rate from 2001 to 2009. The top three injury category descriptions for lost-time incidents within saw-related claims were fracture (35.8%), open wounds (29.6%), and amputation (14.8%). CONCLUSIONS: For saw-related injuries, preventing blade contact remains important but securing the work piece to prevent kickback is also important.

Assessment of fall-arrest systems for scissor lift operators: computer modeling and manikin drop testing.

OBJECTIVE: The current study is intended to evaluate the stability of a scissor lift and the performance of various fall-arrest harnesses/lanyards during drop/fall-arrest conditions and to quantify the dynamic loading to the head/ neck caused by fall-arrest forces. BACKGROUND: No data exist that establish the efficacy of fall-arrest systems for use on scissor lifts or the injury potential from the fall incidents using a fall-arrest system. METHOD: The authors developed a multibody dynamic model of the scissor lift and a human lift operator model using ADAMS and LifeMOD Biomechanics Human Modeler. They evaluated lift stability for four fall-arrest system products and quantified biomechanical impacts on operators during drop/fall arrest, using manikin drop tests. Test conditions were constrained to flat surfaces to isolate the effect of manikin-lanyard interaction. RESULTS: The fully extended scissor lift maintained structural and dynamic stability for all manikin drop test conditions. The maximum arrest forces from the harnesses/lanyards were all within the limits of ANSI Z359.1. The dynamic loading in the lower neck during the fall impact reached a level that is typically observed in automobile crash tests, indicating a potential injury risk for vulnerable participants. CONCLUSION: Fall-arrest systems may function as an effective mechanism for fall injury protection for operators of scissor lifts. However, operators may be subjected to significant biomechanical loadings on the lower neck during fall impact. APPLICATION: Results suggest that scissor lifts retain stability under test conditions approximating human falls from predefined distances but injury could occur to vulnerable body structures.

Estimation of the kinetic energy dissipation in fall-arrest system and manikin during fall impact.

Fall-arrest systems (FASs) have been widely applied to provide a safe stop during fall incidents for occupational activities. The mechanical interaction and kinetic energy exchange between the human body and the fall-arrest system during fall impact is one of the most important factors in FAS ergonomic design. In the current study, we developed a systematic approach to evaluate the energy dissipated in the energy absorbing lanyard (EAL) and in the harness/manikin during fall impact. The kinematics of the manikin and EAL during the impact were derived using the arrest-force time histories that were measured experimentally. We applied the proposed method to analyse the experimental data of drop tests at heights of 1.83 and 3.35 m. Our preliminary results indicate that approximately 84-92% of the kinetic energy is dissipated in the EAL system and the remainder is dissipated in the harness/manikin during fall impact. The proposed approach would be useful for the ergonomic design and performance evaluation of an FAS. STATEMENT OF RELEVANCE: Mechanical interaction, especially kinetic energy exchange, between the human body and the fall-arrest system during fall impact is one of the most important factors in the ergonomic design of a fall-arrest system. In the current study, we propose an approach to quantify the kinetic energy dissipated in the energy absorbing lanyard and in the harness/body system during fall impact.

Fall arrest characteristics of a scissor lift.

PROBLEM: Census of Fatal Occupational Injuries (CFOI) data indicate 306 aerial lift fatalities between 1992-2003. Seventy-eight of these fatalities specifically involved scissor lifts. Members of standards committees have requested that NIOSH conduct research to determine the effects of safety-control practices related to using fall-protection systems for scissor lifts. METHOD: This research examined the structural and dynamic stability of a scissor lift subjected to fall arrest forces. This was accomplished by conducting drop tests from a scissor lift. Anchorage locations evaluated included manufacturer-supplied anchorage points on the scissor lift platform as well as mid-rail and top-rail locations. RESULTS: Preliminary drop tests determined that a 2400 lb maximum arrest force (MAF) could be generated by dropping 169 lb through a fall height of 36" using Nystron rope as a lanyard. The scissor lift maintained structural and dynamic stability for all drop tests when fully extended and on an incline. DISCUSSION: Anchoring a fall arrest system to either the mid-rail or top-rail is not a recommended practice by the scissor lift manufacturer. Anchor points are provided on the platform floor of the scissor lift for this purpose. However, our results demonstrate that the mid-rail and top-rail absorb substantial energy from an arrested fall and may have potential as appropriate anchorage points. IMPACT TO INDUSTRY: Employers and workers should consider implementing fall arrest systems when using scissor lifts as part of their overall risk mitigation plan for fall injury prevention.

Variation in the alpha2B-adrenergic receptor gene (ADRA2B) and its relationship to vascular response in vivo.

The alpha2B-adrenergic receptor (ADRA2B) plays an important role in vasoconstriction and blood pressure regulation. One common variant in the ADRA2B gene (del 301--303) has been identified, and results in markedly decreased receptor desensitization in vitro but does not alter vascular sensitivity in vivo. Therefore, we fully characterized genetic variations in ADRA2B and related them to phenotype in vivo. We examined 5812 bp of contiguous sequence of ADRA2B (promoter, exonic, and 3'-untranslated region; 3'-UTR) using the polymerase chain reaction to amplify the genomic target followed by bidirectional sequencing (n=68). Haplotypes were inferred using an expectation maximization algorithm. Vasoconstriction in response to increasing doses of the highly selective alpha2-adrenergic receptor agonist, dexmedetomidine (0.01--1000 ng/min) was measured in the dorsal hand vein using a linear variable differential transformer. The dose that produced 50% (ED50) of maximum venoconstriction (Emax) was determined for each subject from the individual dose--response curves. ED50 and Emax were compared in subjects with and without variant alleles and haplotypes of interest. We identified 24 variable sites, 12 in the promoter region, five in the coding region (including two previously described as non-synonymous variants) and seven in the 3'-UTR region. Four haplotypes were inferred, representing approximately 95% of the cohort. One haplotype, characterized by two single nucleotide polymorphisms in the promoter region, and one in the 3'-UTR, occurred in seven of 38 African-Americans, and was associated with a lower Emax, 61.3% [95% confidence interval (CI) 39.5--83.0, n=7] compared to 78.1% (CI 73.8--82.5) in wild-types (n=61) (P=0.02). There was no association between the nine common variants and dexmedetomidine ED50. We have described novel variants and haplotypes of the ADRA2B gene. These do not alter sensitivity to a selective alpha2-adrenergic receptor agonist but some may decrease maximal venoconstriction in vivo.

Genetic variation in eleven phase I drug metabolism genes in an ethnically diverse population.

The extent of genetic variation found in drug metabolism genes and its contribution to interindividual variation in response to medication remains incompletely understood. To better determine the identity and frequency of variation in 11 phase I drug metabolism genes, the exons and flanking intronic regions of the cytochrome P450 (CYP) isoenzyme genes CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP3A5 were amplified from genomic DNA and sequenced. A total of 60 kb of bi-directional sequence was generated from each of 93 human DNAs, which included Caucasian, African-American and Asian samples. There were 388 different polymorphisms identified. These included 269 non-coding, 45 synonymous and 74 non-synonymous polymorphisms. Of these, 54% were novel and included 176 non-coding, 14 synonymous and 21 non-synonymous polymorphisms. Of the novel variants observed, 85 were represented by single occurrences of the minor allele in the sample set. Much of the variation observed was from low-frequency alleles. Comparatively, these genes are variation-rich. Calculations measuring genetic diversity revealed that while the values for the individual genes are widely variable, the overall nucleotide diversity of 7.7 x 10(-4) and polymorphism parameter of 11.5 x 10(-4) are higher than those previously reported for other gene sets. Several independent measurements indicate that these genes are under selective pressure, particularly for polymorphisms corresponding to non-synonymous amino acid changes. There is relatively little difference in measurements of diversity among the ethnic groups, but there are large differences among the genes and gene subfamilies themselves. Of the three CYP subfamilies involved in phase I drug metabolism (1, 2, and 3), subfamily 2 displays the highest levels of genetic diversity.