Efficacy of powered air-purifying respirators (PAPRs) for source control of simulated respiratory aerosols.

Background: Loose-fitting powered air-purifying respirators (PAPRs) are a popular alternative to the use of filtering facepiece respirators for health care workers. Although PAPRs protect the wearer from aerosol particles, their ability to block infectious aerosol particles exhaled by the wearer from being released into the environment (called source control) is unclear.

Methods: The source control performance of 4 PAPRs with loose-fitting facepieces were tested using a manikin that exhales aerosol particles.

In vitro inflammation and toxicity assessment of pre- and post-incinerated organomodified nanoclays to macrophages using high-throughput screening approaches.

Background: Organomodified nanoclays (ONC), two-dimensional montmorillonite with organic coatings, are increasingly used to improve nanocomposite properties. However, little is known about pulmonary health risks along the nanoclay life cycle even with increased evidence of airborne particulate exposures in occupational environments. Recently, oropharyngeal aspiration exposure to pre- and post-incinerated ONC in mice caused low grade, persistent lung inflammation with a pro-fibrotic signaling response with unknown mode(s) of action.

Variation in pentose phosphate pathway-associated metabolism dictates cytotoxicity outcomes determined by tetrazolium reduction assays.

Tetrazolium reduction and resazurin assays are the mainstay of routine in vitro toxicity batteries. However, potentially erroneous characterization of cytotoxicity and cell proliferation can arise if verification of baseline interaction of test article with method employed is neglected. The current investigation aimed to demonstrate how interpretation of results from several standard cytotoxicity and proliferation assays vary in dependence on contributions from the pentose phosphate pathway (PPP).

Constant vs. cyclic flow when testing face masks and respirators as source control devices for simulated respiratory aerosols.

SARS-CoV-2 spreads by infectious aerosols and droplets from the respiratory tract. Masks and respirators can reduce the transmission of infectious respiratory diseases by collecting these aerosols at the source. The ability of source control devices to block aerosols can be tested by expelling an aerosol through a headform using constant airflows, which are simpler, or cyclic airflows, which are more realistic but require more complex methods.

Efficacy of Do-It-Yourself air filtration units in reducing exposure to simulated respiratory aerosols.

Many respiratory diseases, including COVID-19, can be spread by aerosols expelled by infected people when they cough, talk, sing, or exhale. Exposure to these aerosols indoors can be reduced by portable air filtration units (air cleaners). Homemade or Do-It-Yourself (DIY) air filtration units are a popular alternative to commercially produced devices, but performance data is limited.

Developing a Solution for Nasal and Olfactory Transport of Nanomaterials.

With advances in nanotechnology, engineered nanomaterial applications are a rapidly growing sector of the economy. Some nanomaterials can reach the brain through nose-to-brain transport. This transport creates concern for potential neurotoxicity of insoluble nanomaterials and a need for toxicity screening tests that detect nose-to-brain transport.

Reduction of exposure to simulated respiratory aerosols using ventilation, physical distancing, and universal masking.

To limit community spread of SARS-CoV-2, CDC recommends universal masking indoors, maintaining 1.8 m of physical distancing, adequate ventilation, and avoiding crowded indoor spaces. Several studies have examined the independent influence of each control strategy in mitigating transmission in isolation, yet controls are often implemented concomitantly within an indoor environment.

Efficacy of Ventilation, HEPA Air Cleaners, Universal Masking, and Physical Distancing for Reducing Exposure to Simulated Exhaled Aerosols in a Meeting Room.

There is strong evidence associating the indoor environment with transmission of SARS-CoV-2, the virus that causes COVID-19. SARS-CoV-2 can spread by exposure to droplets and very fine aerosol particles from respiratory fluids that are released by infected persons. Layered mitigation strategies, including but not limited to maintaining physical distancing, adequate ventilation, universal masking, avoiding overcrowding, and vaccination, have shown to be effective in reducing the spread of SARS-CoV-2 within the indoor environment.

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.

U.S. Federal Agency interests and key considerations for new approach methodologies for nanomaterials.

Engineered nanomaterials (ENMs) come in a wide array of shapes, sizes, surface coatings, and compositions, and often possess novel or enhanced properties compared to larger sized particles of the same elemental composition. To ensure the safe commercialization of products containing ENMs, it is important to thoroughly understand their potential risks. Given that ENMs can be created in an almost infinite number of variations, it is not feasible to conduct in vivo testing on each type of ENM.

Efficacy of universal masking for source control and personal protection from simulated cough and exhaled aerosols in a room.

Face masks reduce the expulsion of respiratory aerosols produced during coughs and exhalations ("source control"). Factors such as the directions in which people are facing (orientation) and separation distance also affect aerosol dispersion. However, it is not clear how the combined effects of masking, orientation, and distance affect the exposure of individuals to respiratory aerosols in indoor spaces.

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.

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.

Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021.

Universal masking is one of the prevention strategies recommended by CDC to slow the spread of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19) (1). As of February 1, 2021, 38 states and the District of Columbia had universal masking mandates. Mask wearing has also been mandated by executive order for federal property* as well as on domestic and international transportation conveyances.

Carbon nanotube filler enhances incinerated thermoplastics-induced cytotoxicity and metabolic disruption in vitro.

Background: Engineered nanomaterials are increasingly being incorporated into synthetic materials as fillers and additives. The potential pathological effects of end-of-lifecycle recycling and disposal of virgin and nano-enabled composites have not been adequately addressed, particularly following incineration. The current investigation aims to characterize the cytotoxicity of incinerated virgin thermoplastics vs.

Iron Oxide Nanoparticle-Induced Neoplastic-Like Cell Transformation Is Reduced with a Protective Amorphous Silica Coating.

Iron oxide nanoparticles (IONP) have recently surged in production and use in a wide variety of biomedical and environmental applications. However, their potential long-term health effects, including carcinogenesis, are unknown. Limited research suggests IONP can induce genotoxicity and neoplastic transformation associated with particle dissolution and release of free iron ions.

Evaluation of tumorigenic potential of CeO and FeO engineered nanoparticles by a human cell screening model.

With rapid development of novel nanotechnologies that incorporate engineered nanomaterials (ENMs) into manufactured products, long-term, low dose ENM exposures in occupational settings is forecasted to occur with potential adverse outcomes to human health. Few ENM human health risk assessment efforts have evaluated tumorigenic potential of ENMs. Two widely used nano-scaled metal oxides (NMOs), cerium oxide (nCeO) and ferric oxide (nFeO) were screened in the current study using a sub-chronic exposure to human primary small airway epithelial cells (pSAECs).

Direct stimulation of human fibroblasts by nCeO2 in vitro is attenuated with an amorphous silica coating.

Background: Nano-scaled cerium oxide (nCeO2) is used in a variety of applications, including use as a fuel additive, catalyst, and polishing agent, yet potential adverse health effects associated with nCeO2 exposure remain incompletely understood. Given the increasing utility and demand for engineered nanomaterials (ENMs) such as nCeO2, "safety-by-design" approaches are currently being sought, meaning that the physicochemical properties (e.g.

Identification of TGF-β receptor-1 as a key regulator of carbon nanotube-induced fibrogenesis.

Carbon nanotubes (CNTs) induce rapid interstitial lung fibrosis, but the underlying mechanisms are unclear. Previous studies indicated that the ability of CNTs to penetrate lung epithelium, enter interstitial tissue, and stimulate fibroblasts to produce collagen matrix is important to lung fibrosis. In this study, we investigated the activation of transforming growth factor-β receptor-1 [TGF-β R1; i.

Potential model for testing the effect of exposure to nanoparticles on the lung alveolar epithelial barrier.

Pulmonary barrier function plays a pivotal role in protection from inhaled particles. However, some nano-scaled particles, such as carbon nanotubes (CNT), have demonstrated the ability to penetrate this barrier in animal models, resulting in an unusual, rapid interstitial fibrosis. To delineate the underlying mechanism and specific bio-effect of inhaled nanoparticles in respiratory toxicity, models of lung epithelial barriers are required that allow accurate representation of systems; however, there is currently a lack of consistent methods to do so.

Effect of fiber length on carbon nanotube-induced fibrogenesis.

Given their extremely small size and light weight, carbon nanotubes (CNTs) can be readily inhaled by human lungs resulting in increased rates of pulmonary disorders, particularly fibrosis. Although the fibrogenic potential of CNTs is well established, there is a lack of consensus regarding the contribution of physicochemical attributes of CNTs on the underlying fibrotic outcome. We designed an experimentally validated in vitro fibroblast culture model aimed at investigating the effect of fiber length on single-walled CNT (SWCNT)-induced pulmonary fibrosis.

Estimating the effective density of engineered nanomaterials for in vitro dosimetry.

The need for accurate in vitro dosimetry remains a major obstacle to the development of cost-effective toxicological screening methods for engineered nanomaterials. An important key to accurate in vitro dosimetry is the characterization of sedimentation and diffusion rates of nanoparticles suspended in culture media, which largely depend upon the effective density and diameter of formed agglomerates in suspension. Here we present a rapid and inexpensive method for accurately measuring the effective density of nano-agglomerates in suspension.

Tracking translocation of industrially relevant engineered nanomaterials (ENMs) across alveolar epithelial monolayers in vitro.

Abstract Relatively little is known about the fate of industrially relevant engineered nanomaterials (ENMs) in the lungs that can be used to convert administered doses to delivered doses. Inhalation exposure and subsequent translocation of ENMs across the epithelial lining layer of the lung might contribute to clearance, toxic effects or both. To allow precise quantitation of translocation across lung epithelial cells, we developed a method for tracking industrially relevant metal oxide ENMs in vitro using neutron activation.

Neoplastic-like transformation effect of single-walled and multi-walled carbon nanotubes compared to asbestos on human lung small airway epithelial cells.

Accumulating evidence indicates that carbon nanotubes (CNTs) are biopersistent and can cause lung damage. With similar fibrous morphology and mode of exposure to asbestos, a known human carcinogen, growing concern has arisen for elevated risk of CNT-induced lung carcinogenesis; however, relatively little is known about the long-term carcinogenic effect of CNT. Neoplastic transformation is a key early event leading to carcinogenesis.