Eficacia de la mascarilla facial con filtro de partículas N95 y de la mascarilla quirúrgica durante la respiración humana: dos vías para la penetración de partículas.

RESUMENEl nivel de protección ofrecido por las mascarillas con filtro de partículas y las mascarillas se establece considerando el porcentaje de partículas ambientales que penetran dentro del dispositivo de protección. Existen dos vías de penetración: (1) la infiltración a través del sellado facial de la mascarilla y (2) a través del medio filtrante. El objetivo principal de este estudio fue diferenciar el aporte proveniente de cada una de estas dos vías para partículas cuyo tamaño oscila entre 0.03-1 µm en condiciones de respiración reales. Así, mientras se realizaban pruebas de ajuste convencionales, se evaluaron una mascarilla respiratoria autofiltrante N95 y una mascarilla quirúrgica usada comúnmente en entornos de atención médica en 25 sujetos (número coincidente con el último panel de pruebas de ajuste del Instituto Nacional de Seguridad y Salud Laborales). Asimismo, ambas mascarillas fueron evaluadas empleando maniquíes de respiración que imitaban de forma precisa los patrones de respiración registrados previamente en los sujetos evaluados. Posteriormente, se compararon los datos de penetración obtenidos en las evaluaciones realizadas con sujetos humanos y con maniquíes para determinar los diferentes tamaños de partículas, así como los patrones de respiración. Así se determinaron 5,250 valores de penetración específicos correspondientes al ejercicio y el tamaño de las partículas. Para cada valor se calcularon la tasa de infiltración a través del sellado facial de la mascarilla y la tasa de infiltración a través del filtro, con la finalidad de cuantificar los aportes relativos realizados por cada vía de penetración. El número de partículas que penetra mediante infiltración del sellado facial de la mascarilla autofiltrante/mascarilla quirúrgica probadas excedió ampliamente el número de aquellas que lo hacen a través del filtro. Para la mascarilla autofiltrante N95, el exceso fue (en promedio) de un orden de magnitud y se incrementó notablemente al aumentar el tamaño de las partículas (p < 0.001): ∼7 veces mayor para 0,04 µm, ∼10 veces para 0.1 µm y ∼20 veces para 1 µm. En el caso de la mascarilla quirúrgica, la tasa de infiltración a través del sellado facial de la misma con respecto al filtro osciló entre 4.8 y 5.8 y no se vio significativamente afectada por el tamaño de las partículas para la fracción del submicrómetro evaluado. El movimiento facial/corporal tuvo un efecto pronunciado en el aporte relativo de las dos vías de penetración. La intensidad de la respiración y las dimensiones faciales mostraron alguna influencia (aunque limitada). Considerando que la mayoría de las partículas que penetraron ingresaron a través del sellado facial, al desarrollar la mascarilla autofiltrante/mascarilla quirúrgica la prioridad debería ser realizar una adecuación que permitiera eliminar o minimizar la infiltración a través del sellado facial y no mejorar la eficiencia del medio de filtro.

Effect of fit testing on the protection offered by n95 filtering facepiece respirators against fine particles in a laboratory setting.

OBJECTIVES: This study investigated particle-size-selective protection factors (PFs) of four models of N95 filtering facepiece respirators (FFRs) that passed and failed fit testing. Particle size ranges were representative of individual viruses and bacteria (aerodynamic diameter d(a) = 0.04-1.3 µm). METHODS: Standard respirator fit testing was followed by particle-size-selective measurement of PFs while subjects wore N95 FFRs in a test chamber. PF values obtained for all subjects were then compared to those obtained for the subjects who passed the fit testing. RESULTS: Overall fit test passing rate for all four models of FFRs was 67%. Of these, 29% had PFs <10 (the Occupational Safety and Health Administration Assigned Protection Factor designated for this type of respirator). When only subjects that passed fit testing were included, PFs improved with 9% having values <10. On average, the PFs were 1.4 times (29.5/21.5) higher when only data for those who passed fit testing were included. The minimum PFs were consistently observed in the particle size range of 0.08-0.2 µm. CONCLUSIONS: Overall PFs increased when subjects passed fit testing. The results support the value of fit testing but also show for the first time that PFs are dependent on particle size regardless of fit testing status.

Evaluations of Electrostatic Filtration Efficiency and Antibacterial Efficacy of Antibacterial Electret Polypropylene Filters: Effects of Using Low Molecular Antibacterial Agent as Additive.

In recent years, air filtration has been gaining much attention, and now people are much more concerned about antibacterial filters due to the spreading of COVID-19. The electret polypropylene (PP) nonwoven fabrics possess excellent filtration efficiency but a limited antibacterial effect against S. aureus and E. coli, and therefore triclosan is used in this study. Serving as an antibacterial agent, triclosan with a low molecular weight is an effective additive for the test results, indicating that the presence of triclosan strengthens the antibacterial effects of the filters. In addition, triclosan also strengthens the PP's crystallinity, which in turn betters the filtration efficiency of the filters concurrently. Demonstrating powerful filtration and antibacterial performances, the antibacterial electret PP filters are highly qualified for filter applications.

Performance of an N95 filtering facepiece particulate respirator and a surgical mask during human breathing: two pathways for particle penetration.

The protection level offered by filtering facepiece particulate respirators and face masks is defined by the percentage of ambient particles penetrating inside the protection device. There are two penetration pathways: (1) through the faceseal leakage, and the (2) filter medium. This study aimed at differentiating the contributions of these two pathways for particles in the size range of 0.03-1 microm under actual breathing conditions. One N95 filtering facepiece respirator and one surgical mask commonly used in health care environments were tested on 25 subjects (matching the latest National Institute for Occupational Safety and Health fit testing panel) as the subjects performed conventional fit test exercises. The respirator and the mask were also tested with breathing manikins that precisely mimicked the prerecorded breathing patterns of the tested subjects. The penetration data obtained in the human subject- and manikin-based tests were compared for different particle sizes and breathing patterns. Overall, 5250 particle size- and exercise-specific penetration values were determined. For each value, the faceseal leakage-to-filter ratio was calculated to quantify the relative contributions of the two penetration pathways. The number of particles penetrating through the faceseal leakage of the tested respirator/mask far exceeded the number of those penetrating through the filter medium. For the N95 respirator, the excess was (on average) by an order of magnitude and significantly increased with an increase in particle size (p < 0.001): approximately 7-fold greater for 0.04 microm, approximately 10-fold for 0.1 microm, and approximately 20-fold for 1 microm. For the surgical mask, the faceseal leakage-to-filter ratio ranged from 4.8 to 5.8 and was not significantly affected by the particle size for the tested submicrometer fraction. Facial/body movement had a pronounced effect on the relative contribution of the two penetration pathways. Breathing intensity and facial dimensions showed some (although limited) influence. Because most of the penetrated particles entered through the faceseal, the priority in respirator/mask development should be shifted from improving the efficiency of the filter medium to establishing a better fit that would eliminate or minimize faceseal leakage.

A novel iron-conjugated acid-modified chitosan derivatives as an oral phosphate binding agent to improve phosphorus adsorption efficacy in vitro and in vivo, synthesis and their characterization.

Current phosphate binders used for hyperphosphatemia treatment need large daily dose which make patients' compliance worse and the therapeutic efficacy may not conform the expectation. In this study, three polyacid modified iron-based chitosan derivatives were developed as an oral phosphate binding agent to improve phosphorus adsorption efficacy. The result showed that modification of chitosan by citric acid (CA) could facilitate the conjugation of iron by two folds (272.0 ±â€¯12.1-315.3 ±â€¯20.5 mg Fe/g vs. 141.0 ±â€¯4.9-156.5 ±â€¯8.3 mg Fe/g). All of these iron-based acid-modified chitosan had acceptable safety with cell viability >75% in the concentration up to 250 µg/mL. The stability in terms of iron release in pH 1.0 for 2 h was in the order of DPCS-NAc-CA-Fe (8.9 ±â€¯2.3%) < DPCS-CA-Fe (19.1 ±â€¯4.1%) < DADPCS-CA-Fe (24.6 ±â€¯2.6%) indicating DPCS-NAc-CA-Fe was the most stable one. These iron-based acid-modified chitosan derivatives efficiently adsorbed 255.7 ±â€¯11.3-271.2 ±â€¯19.3 mg of phosphate especially in simulated gastro pH 1.0 in vitro. Furthermore, oral administration of DPCS-NAc-CA-Fe significantly lowered serum phosphorus level from 5.82 ±â€¯0.45 mg/dL to 4.84 ±â€¯0.56 mg/dL (p < 0.01) at 0.25% low feeding dose for 3 weeks without losing of weight, appetite, and activity of Wistar rats.

Respiratory performance offered by N95 respirators and surgical masks: human subject evaluation with NaCl aerosol representing bacterial and viral particle size range.

OBJECTIVES: This study aimed at determining the protection factors (PFs) provided by N95 filtering facepiece respirators and surgical masks against particles representing bacterial and viral size ranges (aerodynamic size: 0.04-1.3 mum). METHODS: The protection levels of N95 filtering facepiece respirators (four models) and surgical masks (three models) were investigated while they were donned by 12 subjects performing the OSHA (US Occupational Safety and Health Administration) fit-testing exercises in a test chamber. RESULTS: About 29% of N95 respirators and approximately 100% of surgical masks had PFs <10, which is the assigned PF designated for this type of respirator by the OSHA. On average, the PFs of N95 respirators were 8-12 times greater than those of surgical masks. The minimum PFs were observed in the size range of 0.04-0.2 mum. No significant difference in PF results was found between N95 respirators with and without an exhalation valve. CONCLUSIONS: The study indicates that N95 filtering facepiece respirators may not achieve the expected protection level against bacteria and viruses. An exhalation valve on the N95 respirator does not affect the respiratory protection; it appears to be an appropriate alternative to reduce the breathing resistance.

Particle Size-Selective Assessment of Protection of European Standard FFP Respirators and Surgical Masks against Particles-Tested with Human Subjects.

This study was conducted to investigate the protection of disposable filtering half-facepiece respirators of different grades against particles between 0.093 and 1.61 µm. A personal sampling system was used to particle size-selectively assess the protection of respirators. The results show that about 10.9% of FFP2 respirators and 28.2% of FFP3 respirators demonstrate assigned protection factors (APFs) below 10 and 20, which are the levels assigned for these respirators by the British Standard. On average, the protection factors of FFP respirators were 11.5 to 15.9 times greater than those of surgical masks. The minimum protection factors (PFs) were observed for particles between 0.263 and 0.384 µm. No significant difference in PF results was found among FFP respirator categories and particle size. A strong association between fit factors and protection factors was found. The study indicates that FFP respirators may not achieve the expected protection level and the APFs may need to be revised for these classes of respirators.

Assessment of human exposure to airborne fungi in agricultural confinements: personal inhalable sampling versus stationary sampling.

Accurate exposure assessment to airborne fungi in agricultural environments is essential for estimating the associated occupational health hazards of workers. The objective of this pilot study was to compare personal and stationary sampling for assessing farmers' exposure to airborne fungi in 3 different agricultural confinements located in Ohio, USA (hog farm, dairy farm, and grain farm), using Button Personal Inhalable Samplers. Personal exposures were measured with samplers worn by 3 subjects (each carrying 2 samplers) during 3 types of activities, including animal feeding in the hog farm, cleaning and animal handling in the dairy farm, and soybean unloading and handling in the grain farm. Simultaneously, the stationary measurements were performed using 5 static Button Samplers and 1 revolving Button Sampler. The study showed that the total concentration of airborne fungi ranged from 1.4 x 10(4)-1.2 x 10(5) spores m(-3) in 3 confinements. Grain unloading and handling activity generated highest concentrations of airborne fungi compared to the other 2 activities. Prevalent airborne fungi belonged to Cladosporium, Aspergillus/Penicillium, Ascospores, smut spores, Epicoccum, Alternaria, and Basidiospores. Lower coefficients of variations were observed for the fungal concentrations measured by personal samplers (7-12%) compared to the concentrations measured by stationary samplers (27-37%). No statistically significant difference was observed between the stationary and personal measurement data for the total concentrations of airborne fungi (p > 0.05). Revolving stationary and static stationary Button Samplers demonstrated similar performance characteristics for the collection of airborne fungi. This reflects the low sensitivity of the sampler's efficiency to the wind speed and direction. The results indicate that personal exposure of agricultural workers in confinements may be adequately assessed by placing several Button Samplers simultaneously operating in a static stationary mode throughout the work site.

Size-selective assessment of agricultural workers' personal exposure to airborne fungi and fungal fragments.

Fungi are ubiquitous agents that cause human respiratory diseases. Very few studies have size-selectively assessed farmers' exposure to fungi and fungal fragments in agricultural settings. In this study, a two-stage bio-aerosol cyclone personal sampler was employed to collect airborne fungi and fungal fragments size-selectively at corn, swine, poultry, and mushroom farms. The collected air samples were analyzed for culturable fungi, fungal spores, viable fungi and (1 → 3)-ß-D-glucan. The results show that the median concentrations ranged from 3.2 × 10(5) to 1.3 × 10(8)spores/m(3) for total fungal spores, from 1.3 × 10(5) to 5.1 × 10(7)spores/m(3) for total viable fungi, from 1.9 × 10(3) to 1.5 × 10(7)CFU/m(3) for total culturable fungi, and from 4.3 × 10(3) to 2.4 × 10(6)pg/m(3) for total (1 → 3)-ß-D-glucan. The aerodynamic sizes of most of the collected fungal contaminants were larger than 1.8 µm. Total (1 → 3)-ß-D-glucan significantly correlated with total fungal spores (r = 0.65, p < 0.001), total viable fungi (r = 0.68, p < 0.001) and total culturable fungi (r = 0.72, p < 0.001). Total (1 → 3)-ß-D-glucan significantly correlated with Aspergillus/Penicillium, Alternaria, and Cladosporium. Alternaria and Botrytis were also found to highly correlate with (1 → 3)-ß-D-glucan at the size <1 µm, which was less than the expected spore sizes (the mean measured aerodynamic sizes were 18.5 µm for Alternaria and 6.1 µm for Botrytis); therefore, Alternaria and Botrytis might release small fragments that could enter the deep lung and cause respiratory diseases.

PM2.5 and associated polycyclic aromatic hydrocarbon and mutagenicity emissions from motorcycles.

In this study, PM(2.5) in diluted exhausts of motorcycles are collected and emission characteristics of PM(2.5)-associated polycyclic aromatic hydrocarbons (PAHs) and mutagenicities are investigated. The measured mutagenicity emission factors with metabolic activation for new fuel injection, used fuel injection, new carburetor and used carburetor motorcycles are 7.77 x 10(4), 1.18 x 10(5), 1.32 x 10(5) and 1.15 x 10(5) rev/km, respectively. The mutagenicity emission factors with metabolic activation are higher than the corresponding values without metabolic activation. The average PAH emission factors are 12.3, 16.3, 25.5 and 26.5 microg/km for new and used fuel-injection motorcycles, and new and used carburetor-operated motorcycles, respectively. The correlation coefficients between PAHs and mutagenicity emission factors are higher with metabolic activation (0.59) than that without metabolic activation (0.31).

Size distribution of airborne mist and endotoxin-containing particles in metalworking fluid environments.

The objective of the study was to investigate size-selective concentrations of airborne particles and endotoxin in metalworking fluid (MWF) environments. The experiments were conducted under two conditions: (1) MWF collected in the field was aerosolized with a laboratory-scale simulator (MWF simulator) in the laboratory; and (2) MWFs were aerosolized during routine field operations. All experiments included size-selective measurement of airborne concentrations of particle numbers and endotoxin mass using an electrical low-pressure impactor. During field sampling, the total microbial and endotoxin concentrations in the air were also measured with a BioSampler, and the mass concentration of MWF mists was measured with a photometer. Airborne particle concentrations were highest in the fine particle size ranges in the areas affected by MWFs. Relatively high concentrations of endotoxin were detected at particle size below 0.39 mum, which is smaller than the size of intact bacterial cells. The total microbial and endotoxin analysis revealed high microbial contamination in one sampling site although the total particle mass was not elevated. It was concluded that MWF sites can be contaminated with high concentrations of fine particles, and these fine particles may contain microbial components, such as endotoxin. The results call for the size-selective measurement of particles and endotoxin for more comprehensive exposure assessment in MWF facilities.

Personal exposure to airborne dust and microorganisms in agricultural environments.

Airborne dust and microorganisms are associated with respiratory diseases and increased mortality and morbidity. Farmers are at high risk of exposure to both of these hazards. Very limited information, however, is available on the combined exposures to both hazards on different types of farms. Moreover, most of the previous studies have measured the mass concentration of particles ignoring the particle size. In this study, farmers' exposure to airborne dust and microorganisms was studied using our newly developed personal sampling system. Particle number concentration and size distribution were measured with an optical particle counter. Simultaneously, particles were collected on a filter and analyzed for microorganisms. The field measurements were conducted in animal confinements (swine, poultry, and dairy) and during grain harvesting (corn and soybean). The results show the following average concentrations on the workers' breathing zone: 1.7 x 10(6) to 2.9 x 10(7) particles/m(3) for total dust, 0.9 x 10(3) to 3.9 x 10(4) spores/m(3) for total fungal spores, 0.3 x 10(3) to 3.6 x 10(4)CFU/m(3) for culturable fungal spores, 0.3 x 10(4) to 3.3 x 10(8) CFU/m(3) for culturable bacteria, and limit of detection (LOD) to 2.8 x 10(3) CFU/m(3) for culturable actinomycetes in animal confinements. The respective concentrations were 4.4 x 10(6) to 5.8 x 10(7) particles/m(3), 3.4 x 10(4) to 6.1 x 10(6) spores/m(3), 8.2 x 10(4) to 7.4 x 10(6) CFU/m(3), 0.4 x 10(5) to 1.4 x 10(6) CFU/m(3), and LOD to 2.6 x 10(4) CFU/m(3) during grain harvesting. The highest contribution of large particles (3-10 microm) in total particles was found during grain harvesting, whereas the size distribution was dominated by smaller particles (< 3 microm) in animal confinements. High fraction (up to 37%) of particles between 2-10 microm was found to be fungal spores. The results indicate that an increase in the concentration of large dust particles (2-10 microm) during grain harvesting was partially attributed to the increase in the concentration of the fungal spores. Overall, the combined exposure to airborne dust and microorganisms was found to be more severe during harvesting than in animal confinements.

Laboratory and field evaluation of a new personal sampling system for assessing the protection provided by the N95 filtering facepiece respirators against particles.

OBJECTIVES: We have recently developed a new personal sampling system for the real-time measurement of the protection provided by respirators against airborne dust and micro-organisms. The objective of this study was to evaluate the performance characteristics of the new sampling system in both laboratory and field conditions. METHODS: The measurements were conducted using the N95 filtering facepiece respirators and the newly developed personal sampling system put on a manikin (laboratory study) or donned by a human subject (laboratory and field studies). Two inhalation flow rates (0 and 40 l min(-1)) in conjunction with the sampling flow rate (10 l min(-1)) were tested in the manikin-based experiments to investigate the effects of the leak location (nose, cheek and chin) and the depth of the sampling probe (0, 5, 10 and 15 mm) within the respirator. The effect of human activity on the protection factor was evaluated using a variety of head movements and breathing patterns when a human subject wore the respirator in a room-size laboratory test chamber. The field study was conducted during corn harvesting with a respirator worn by a human subject on a combine. RESULTS: There was no significant difference in the protection factors for different leak locations, or for sampling probe depths, when the inhalation rate was 0 l min(-1). For the inhalation rate of 40 l min(-1), the protection factors for nose leaks were higher than those for chin and cheek leaks. Furthermore, the protection factor was the lowest and showed the least variation when the sampling probe depth was equal to 0 mm (imbedded on the respirator surface). Human subject testing showed that the grimace maneuver decreased the protection factor and changed the original respirator fit. The protection factor during breath holding was lower than that found during inhalation and exhalation. Field results showed greater variation than laboratory results. CONCLUSIONS: The newly designed personal sampling system efficiently detected the changes in protection factors in real time. The sampling flow was least affected by the inhalation flow when the sampling probe was imbedded on the respirator surface. Leak location, breathing patterns and exercises did affect the measurement of the protection factors obtained using an N95 filtering facepiece respirator. This can be attributed to the differences in the in-mask airflow dynamics contributed by the leak, filter material, sampling probe and inhalation. In future studies, it would be beneficial if the laboratory data could be integrated with the field database.

Respiratory protection provided by N95 filtering facepiece respirators against airborne dust and microorganisms in agricultural farms.

A new system was used to determine the workplace protection factors (WPF) for dust and bioaerosols in agricultural environments. The field study was performed with a subject wearing an N95 filtering facepiece respirator while performing animal feeding, grain harvesting and unloading, and routine investigation of facilities. As expected, the geometric means (GM) of the WPFs increased with increasing particle size ranging from 21 for 0.7-1 microm particles to 270 for 5-10 microm particles (p < 0.001). The WPF for total culturable fungi (GM = 35) was significantly greater than for total culturable bacteria (GM = 9) (p = 0.01). Among the different microorganism groups, the WPFs of Cladosporium, culturable fungi, and total fungi were significantly correlated with the WPFs of particles of the same sizes. As compared with the WPFs for dust particles, the WPFs for bioaerosols were found more frequently below 10, which is a recommended assigned protection factor (APF) for N95 filtering facepiece respirators. More than 50% of the WPFs for microorganisms (mean aerodynamic diameter < 5 microm) were less than the proposed APF of 10. Even lower WPFs were calculated after correcting for dead space and lung deposition. Thus, the APF of 10 for N95 filtering facepiece respirators seems inadequate against microorganisms (mean aerodynamic size < 5 microm). These results provide useful pilot data to establish guidelines for respiratory protection against airborne dust and microorganisms on agricultural farms. The method is a promising tool for further epidemiological and intervention studies in agricultural and other similar occupational and nonoccupational environments.

Assessment of electrical charge on airborne microorganisms by a new bioaerosol sampling method.

Bioaerosol sampling is necessary to monitor and control human exposure to harmful airborne microorganisms. An important parameter affecting the collection of airborne microorganisms is the electrical charge on the microorganisms. Using a new design of an electrostatic precipitator (ESP) for bioaerosol sampling, the polarity and relative strength of the electrical charges on airborne microorganisms were determined in several laboratory and field environments by measuring the overall physical collection efficiency and the biological collection efficiency at specific precipitation voltages and polarities. First, bacteria, fungal spores, and dust dispersed from soiled carpets were sampled in a walk-in test chamber. Second, a simulant of anthrax-causing Bacillus anthracis spores was dispersed and sampled in the same chamber. Third, bacteria were sampled in a small office while four adults were engaged in lively discussions. Fourth, bacteria and fungal spores released from hay and horse manure were sampled in a horse barn during cleanup operations. Fifth, bacteria in metalworking fluid droplets were sampled in a metalworking simulator. It was found that the new ESP differentiates between positively and negatively charged microorganisms, and that in most of the tested environments the airborne microorganisms had a net negative charge. This adds a signature to the sampled microorganisms that may assist in their identification or differentiation, for example, in an anti-bioterrorism network.