ABSTRACT
The use of face masks is mandatory in public places in many countries to slow the spread of the COVID-19 pandemic. In developing countries, homemade masks with varying techniques and fabrics are used on the streets. On these fabric masks, the protection against SARS-CoV-2 varies significantly. The most common mask types are N95, surgical masks, and homemade nonwoven and cotton masks. The performance of 227 different face masks used in Brazil was evaluated to quantify their breathability and filtration efficiency (FE) for airborne particles. FE values were measured using NaCl aerosol particles sized from 60 to 300 nm and at 300 nm, minimum efficiency. The differential pressure drop over the mask and the FEmin at 300 nm was used to calculate the mask Quality Factor (QF). The N95 masks showed the highest FE60-300, around 0.98, and a QF of 13.2 KPa−1, and were considered the reference for evaluating homemade masks performance. Surgical masks have an FE60-300 of 0.89, with a good QF of 15.9 KPa−1. Nonwoven masks showed an average FE60-300 of 0.78, with an excellent QF of 24.9 KPa−1, and can be regarded as the best material for homemade masks. The most commonly used material for homemade masks, cotton fabrics, showed significant variability in FE60-300, ranging from a low 0.20 to 0.60, with a low QF of 1.4 KPa−1. Masks always reduce droplets and aerosols emitted by COVID-19 symptomatic and asymptomatic persons, reducing SARS-CoV-2 contamination. [ABSTRACT FROM AUTHOR] Copyright of Aerosol Science & Technology is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
ABSTRACT
abstract We are entering an era in which our planet and our society face major crises. We live simultaneously with three important emergencies: 1) the health crisis, intensified by the Covid-19 pandemic;2) the biodiversity loss crisis;and 3) the climatic emergency. It should be noted that these crises have profound links between them, and also important differences, but they all have strong social and economic impacts and affect the planet globally. They are the result of an economic model that favors development at any cost and very quick profits even at the expense of sustainability. The Covid-19 crisis posed important questions from the viewpoint of a lack of global governance. In turn, the climate crisis has the potential for very serious socio-economic damage, and its effects are already clearly visible. The loss of biodiversity puts our food security at risk, and the balance of the terrestrial system as well. The Amazon, for example, harbors thousands of viruses in its fauna and flora, and if the unrestrained process of occupation continues, new viruses similar to Sars-CoV-2 will possibly come into contact with our society. Overcoming these three crises requires drastic changes in our economic system, unsustainable in its current format. Continued economic growth on a planet with finite natural resources is not possible. Inequality in developing countries and even between nations is explosive and unfair. We will need a new system of global governance that is able to harmonize measures from different countries, states and municipalities. Sustainability on our planet is possible and necessary. We - the scientific community, society, governments and other stakeholders -will have a lot of work ahead of us in the coming years. We have no alternative but to build a new, more just and sustainable society.