Processing and Quality Control of Masks: A Review

Two-Dimensional Piezoelectric Nanofibrous Webs by Self-Polarized Assembly for High-Performance PM0.3 Filtration

Particulate matter (PM) pollution has posed a serious threat to public health, especially the global spread of infectious diseases. Most existing air filtration materials are still subjected to a compromise between removal efficiency and air permeability on account of their stacking bulk structures. Here, we proposed a self-polarized assembly technique to create two-dimensional piezoelectric nanofibrous webs (PNWs) directly from polymer solutions. The strategy involves droplets deforming into ultrathin liquid films by inertial flow, liquid films evolving into web-like architectures by instantaneous phase inversion, and enhanced dipole alignment by cluster electrostatics. The assembled continuous webs exhibit integrated structural superiorities of nanoscale diameters (∼20 nm) of the internal fibers and through pores (∼100 nm). Combined with the wind-driven electrostatic property derived from the enhanced piezoelectricity, the PNW filter shows high efficiency (99.48%) and low air resistance (34 Pa) against PM0.3 as well as high transparency (84%), superlight weight (0.7 g m-2), and long-term stable service life. This creation of such versatile nanomaterials may offer insight into the design and upgrading of high-performance filters.

Masks and respirators for prevention of respiratory infections: a state of the science review

SUMMARYThis narrative review and meta-analysis summarizes a broad evidence base on the benefits-and also the practicalities, disbenefits, harms and personal, sociocultural and environmental impacts-of masks and masking. Our synthesis of evidence from over 100 published reviews and selected primary studies, including re-analyzing contested meta-analyses of key clinical trials, produced seven key findings. First, there is strong and consistent evidence for airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory pathogens. Second, masks are, if correctly and consistently worn, effective in reducing transmission of respiratory diseases and show a dose-response effect. Third, respirators are significantly more effective than medical or cloth masks. Fourth, mask mandates are, overall, effective in reducing community transmission of respiratory pathogens. Fifth, masks are important sociocultural symbols; non-adherence to masking is sometimes linked to political and ideological beliefs and to widely circulated mis- or disinformation. Sixth, while there is much evidence that masks are not generally harmful to the general population, masking may be relatively contraindicated in individuals with certain medical conditions, who may require exemption. Furthermore, certain groups (notably D/deaf people) are disadvantaged when others are masked. Finally, there are risks to the environment from single-use masks and respirators. We propose an agenda for future research, including improved characterization of the situations in which masking should be recommended or mandated; attention to comfort and acceptability; generalized and disability-focused communication support in settings where masks are worn; and development and testing of novel materials and designs for improved filtration, breathability, and environmental impact.

Protective face mask: an effective weapon against SARS-CoV-2 with controlled environmental pollution

Masks are face coverings that give protection from infectious agents, airborne pathogens, bacteria, viruses, surgical fog, dust, and other chemical hazards by acting as a barrier between the wearer and the environment. In the COVID-19 pandemic, this major personal protective equipment's became essential part of our daily life. The aim of this review is to analyze and discuss the different types of masks with their pros and cons, manufacturing procedures, evaluation criteria, and application with some of the sterilization process for reuse and smart mask. The review used a thorough examination of the literature to analyze the preventive effects of surgical, N95, smart mask, and potential environmental damage from those masks. Several studies and evidence were also examined to understand the efficiency of different mask on different environment. N95 respirators are capable of filtering out non-oil-based 95% air-born particles, and surgical masks act as a protective barrier between the wearer and the environment. The application of spoon bond and melt blown techniques in the fabrication process of those masks improves their protective nature and makes them lightweight and comfortable. But the high demand and low supply forced users to reuse and extend their use after sterilizations, even though those masks are recommended to be used once. Universal masking in the SARS-COV-2 pandemic increased the chance of environmental pollution, so the application of smart masks became essential because of their high protection power and self-sterilizing and reusing capabilities.

Extending the Protection Ability and Life Cycle of Medical Masks through the Washing Process

The reuse of decontaminated disposable medical face masks can contribute to reducing the environmental burden of discarded masks. This research is focused on the effect of household and laboratory washing at 50 °C on the quality and functionality of the nonwoven structure of polypropylene medical masks by varying the washing procedure, bath composition, disinfectant agent, and number of washing cycles as a basis for reusability. The barrier properties of the medical mask were analyzed before and after the first and fifth washing cycle indirectly by measuring the contact angle of the liquid droplets with the front and back surface of the mask, further by measuring air permeability and determining antimicrobial resistance. Additional analysis included FTIR, pH of the material surface and aqueous extract, as well as the determination of residual substances-surfactants-in the aqueous extract of washed versus unwashed medical masks, while their aesthetic aspect was examined by measuring their spectral characteristics. The results showed that household washing had a stronger impact on the change of some functional properties, primarily air permeability, than laboratory washing. The addition of the disinfectant agent, didecyldimethylammonium chloride, contributes to the protective ability and supports the idea that washing of medical masks under controlled conditions can preserve barrier properties and enable reusability.

Dynamic variation and inhalation exposure of organophosphates esters and phthalic acid esters in face masks

The coronavirus pandemic (COVID-19) has posed a huge global health threat since December 2019. Wearing face masks is known as an effective measure for controlling the wide spread of COVID-19 and its variants. But on the other hand, face masks could be a potential source of organophosphate esters (OPEs) and phthalic acid esters (PAEs) as they are extensively added in masks. However, knowledge associated with the occurrence as well as inhalation risks of OPEs and PAEs in masks is limited. In this study, OPEs and PAEs were determined in different types of mask samples collected from the local market. OPEs and PAEs were detected in mask samples ranging from 36.7 to 855 ng/g, and from 251 to 3830 ng/g, respectively. Relatively lower OPEs and PAEs concentrations were observed in disposable mask for toddlers. Simulated inhalation experiment indicated that the mass loss of OPEs and PAEs was 136 and 3910 ng/mask in disposable masks, 71.9 and 763 ng/mask in disposable mask for toddlers, 924 and 1020 ng/mask in N95 mask after 12 h, respectively. Significantly negative correlations were exhibited between the decrement of OPEs in masks and the increment of OPEs in corresponding polyurethane foams (PUFs) during the course, elucidating OPEs released from masks could be well captured by PUFs. With regard to the variation over time, predominant OPE and PAE analogues showed semblable release and absorption tendency in mask and corresponding PUF. Inhalation exposure risk of OPEs and PAEs was estimated based on the increment of pollutants in PUF. The estimated daily intakes (EDIs), hazard index (HI) and carcinogenic risk (CR) were also calculated and they were within the threshold levels. This study provides the evidence of OPEs and PAEs releasing from the face masks during wearing and unveiled a potential source of OPEs and PAEs exposure to humans.

Assessment of Different Experimental Setups to Determine Viral Filtration Efficiency of Face Masks

As a result of the COVID-19 pandemic, many new materials and masks came onto the market. To determine their suitability, several standards specify which properties to test, including bacterial filtration efficiency (BFE), while none describe how to determine viral filtration efficiency (VFE), a property that is particularly important in times of pandemic. Therefore, we focused our research on evaluating the suitability and efficiency of different systems for determining VFE. Here, we evaluated the VFE of 6 mask types (e.g., a surgical mask, a respirator, material for mask production, and cloth masks) with different filtration efficiencies in four experimental setups and compared the results with BFE results. The study included 17 BFE and 22 VFE experiments with 73 and 81 mask samples tested, respectively. We have shown that the masks tested had high VFE (>99% for surgical masks and respirators, ≥98% for material, and 87-97% for cloth masks) and that all experimental setups provided highly reproducible and reliable VFE results (coefficient of variation < 6%). Therefore, the VFE tests described in this study can be integrated into existing standards for mask testing.