Proyecto Estudiantil: Prueba de la Eficiencia de Filtración de Algunos Tipos de Máscaras Comunes

por John Garcia Almazán, Maria Di Landro, y Sandhya Sethuraman

Unas mascarillas N95, KF94, y quirúrgica
Unas mascarillas N95, KF94, y quirúrgica. Foto por V.F. McNeill

Los Estados Unidos ha entrado en su tercer año desde el primer caso del coronavirus (COVID-19) confirmado en el país. Debido a las vacunas y otros medidas de salud pública, los casos de COVID-19 están bajo control hoy, pero la enfermedad sigue siendo altamente transmisible y, a veces, peligrosa. En este artículo, consideramos opciones de equipo de protección personal (EPP) en forma de máscaras faciales. Mascarillas que filtran bien la materia particular del aire que inhalamos son valiosas para prevenir infecciones. Teniendo en cuenta la escasez de máscaras y la presencia de mascarillas falsificadas en el mercado, es importante saber qué máscaras disponibles al público son realmente eficientes y efectivas para prevenir la propagación de COVID-19.

Realizamos varios experimentos en una cámara climática. Una muestra del material de diferentes marcas de máscaras estuvo expuesto a partículas pequeñas (10-800 nm). Seguimos las líneas directrices de NIOSH y probamos la filtración de partículas de NaCl a tres velocidades faciales diferentes, midiendo la eficiencia de filtración (la eficacia de las máscaras para proteger al usuario de estas partículas) en función del tamaño de las partículas.

Eficiencia de filtración del material de una mascarilla quirúrgica negra, medida para varios tamaños de partículas y tres velocidades faciales
Tipo de máscara5.3 cm/s10 cm/s15 cm/s
3M Aura (N95)979797
máscara quirúrgica negra889178
Dr. Puri KF94989595
Eficiencia de filtración general (%) para tres tipos de máscara facial, y tres velocidades faciales.

Observamos eficiencias de filtración consistentes con las especificaciones del fabricante para N95, KN95, KF94 y mascarillas quirúrgicas. Las máscaras N95 (3M Aura) demostraron la mayor eficiencia de filtración en todas las categorías, pero incluso el material de la máscara quirúrgicas negras o azules que generalmente se encuentran en oficinas y edificios públicos filtró la mayoría de las partículas.

En esta obra solo examinamos la filtración de muestras del material de mascarillas. En realidad, el ajuste de la máscara y el uso también son muy importantes para saber la eficacia de las máscaras para proteger al usuario.

How wildfires deplete stratospheric ozone

A pyrocumulonimbus cloud over the Alpine National Park, Australia, during the 2019-2020 fires
A pyrocumulonimbus cloud over the Alpine National Park, Australia, during the 2019-2020 fires. Credit: Merrin Macleod, Wikimedia Commons

After the Australian wildfires of the “Black Summer” of 2019-2020, satellite measurements showed a decrease in the stratospheric ozone layer. At the time, scientists connected the decrease in ozone to smoke from the fires that penetrated into the stratosphere, however, the role that smoke particles play in ozone chemistry was still unclear. In a paper published in Nature last week, Susan Solomon and colleagues show that if smoke particles, which contain oxygenated organic material and water, are liquid in the stratosphere, they are capable of absorbing HCl gas and hosting reactions with other “chlorine reservoir” gases such as ClONO2 and HOCl. In this manner, they can drive ozone depletion much like other stratospheric particles. As large wildfires become more common in a changing climate, this phenomenon may slow down the recovery of the stratospheric “ozone hole”.

For the article and more discussion:

ICYMI: India’s Air Pollution Crisis, By the Numbers

In this article, published in October 2017 on HuffPost India, Prof. McNeill and Dr. Julia Nunes break down the data for particulate air pollution in cities across India. Air pollution is at an unhealthy level for a large part of the year, in most Indian cities.

The pie charts show the number of days in the past year that the average PM2.5 level fell into the following three categories: Green days (PM2.5 < 35.4 μg m-3) are healthy or moderate, yellow days (35.5 μg m-3 to 55.4 μg m-3) are unhealthy for sensitive groups such as children, the elderly or those with lung disease, and red days (PM2.5 > 55.5 μg m-3) are unhealthy for all. For more information on the data sources:


Live reporting from Beijing: Air Quality in Crisis

V. Faye McNeill, Beijing, China, December 21, 2016

Haze over central Beijing, 12/20/2016. Photo credit: V. F. McNeill

Much of China, including the capital city, Beijing, is experiencing sustained heavy smog this week, with air pollution at hazardous levels for the past three days. Concentrations of fine particulate matter in Beijing’s air today exceeded 400 ug/m3, more than ten times China’s National Ambient Air Quality Standard (35 ug/m3). The episode has caused an increase in hospitalizations and disruptions in air traffic due to poor visibility. The government has declared a “red alert” and taken emergency measures including industrial shutdowns, odd-even traffic restrictions, and school cancellations to protect public health.

“I love Beijing.  I grew up here and spent my whole life here.  If it weren’t for the air pollution, I would love living here.  But now I think about leaving. Many people are leaving.”

Reduced visibility at Beijing’s airport. 12/20/2016 Photo credit: V.F. McNeill

Air quality is an ongoing issue in Beijing, and a major subject of concern for its residents. As one Beijing native told me: “I love Beijing.  I grew up here and spent my whole life here.  If it weren’t for the air pollution, I would love living here.  But now I think about leaving. Many people are leaving.” According to the U.S. Embassy, between 2008-2015, the daily average air quality index in Beijing fell in the “Unhealthy,” “Very Unhealthy,” or “Hazardous” categories 67% of the time. A severe air quality episode in January 2013 was somewhat of a turning point, leading to increased pressure on the government to tighten regulations. One outcome was the amendment of the national ambient air quality standards. Meeting the new standards for PM2.5 would be a major step towards protecting public health. But, as episodes like this one show, improvement is slow to come. Plans for local implementation and enforcement of the new air quality standards are still in the development stages. In some cases major changes in infrastructure are needed in order to reduce emissions, and this can take time. Local efforts alone won’t be enough: The city of Beijing has made bold moves towards eliminating coal burning within the city, but much of Beijing’s pollution comes from upwind sources, outside the city limits.

With the will of government and the people aligned, China is poised to turn around its air pollution problem. Unlike the U.S., which greatly improved its air quality in the last century and now must tackle climate, China is in a position to develop smart new policies and technology to improve air quality and reduce carbon emissions simultaneously.

Recommended Resource: “What’s Up in the Atmosphere? Exploring Colors in the Sky,” an aerosols storybook from The GLOBE Program

Scientists and educators from NASA and UCAR have written a storybook entitled “What’s Up in the Atmosphere? Exploring Colors in the Sky” aimed at elementary school-aged (K-4) children, in which atmospheric aerosols play a starring role.  The story follows a group of curious students who, under the guidance of their teacher, investigate the connection between the appearance of the sky and asthma symptoms in their fellow students on a given day.  The students in the story (and the readers) learn about atmospheric aerosols in the process.  The storybook includes a teachers’ guide with glossary.

Air Quality in Manila, Philippines

The AIRE team spends a few weeks every year visiting family in Manila, Philippines.  Like many vibrant megacities, Manila suffers from heavy traffic and poor air quality.  Starting in Summer 2015, the Philippine government has made real-time air quality monitoring data available from stations around Metro Manila.  Interested citizens can look up current PM2.5 levels and compare them to the 24 hour guideline value.  We note that the EMB 24 hr guideline value is 75 micrograms/m3, whereas the United States EPA 24-hour average PM2.5 standard is 35 micrograms/m3 (the yearly average standard is 15 micrograms/m3).

Recommended Resource: Aerosol Science & Engineering

In honor of the 2014 Annual meeting of the American Association for Aerosol Research, happening this week in Orlando, FL,  we are very excited to share with you this series of educational modules on the science and engineering of aerosols (airborne particles).

These materials were developed by Profs. Pratim Biswas, of Washington University St. Louis, and C. Y. Wu, of University of Florida, through a collaborative grant from the National Science Foundation. The modules are aimed at an introductory college level, and are excellent for supplementing course materials or learning on your own.

The modules:

The complete lecture series for an introductory course on Aerosol Science and Technology from WUStL is available FREE through ITunesU!:

Additional information on this effort, and more resources: