Standards Behind the Mask
Prior to the COVID-19 pandemic, most people didn’t think too much about masks. And if they did, it was probably in the context of what they’d wear to an upcoming Halloween party.
Of course, medical professionals and others who wear masks on the job have always taken a more serious view of what for them is a vital piece of protective gear. But few questioned basic aspects of mask design and usage.
SARS-CoV-2 changed all that. The newest member of the coronavirus family — a group of RNA viruses that cause respiratory tract infections in humans and other mammals —was first identified toward the end of 2019. By the spring of 2020, it was spreading rapidly and the infection it caused, COVID-19, was causing fatalities and disrupting social life across the globe.
Epidemiologists and the public health community struggled, especially in the early days of the pandemic, to understand just how the virus was most likely to be transmitted and how best to avoid it. The sometimes contentious debate led to a much sharper focus on masks and other forms of personal protective equipment (PPE). The degree to which this equipment was able to shield wearers from the virus became, quite literally, a matter of life and death.
As healthcare workers, government officials, and everyday people grappled with these questions in the early months of the outbreak, members of ASTM International’s committee on protective clothing (F23) were already hard at work on improved standards for masks and other wearables. Their efforts just might shape the future of PPE.
Spring of 2020 was a troubling time. Stories on the spread of SARS-CoV-2 began to dominate the news, and people began to become infected in increasing numbers. One result was heightened attention to methods of protecting individuals from the virus. But so much was still unknown.
“When the pandemic first arose, the mode of disease transmission was uncertain. Many can remember where initial concerns were for contaminated surfaces such as packages or items picked up at the supermarket,” says Jeff Stull. A member of numerous committees (including F23) and president of International Personnel Protection, Stull had an insider’s view of the urgent search for answers.
He believes that the widely reported shortages of PPE, particularly among healthcare providers, helped highlight how crucial the right equipment was for effective disease prevention, and further notes that this increased attention fostered a more granular approach to PPE evaluation. “The pandemic framed how design and material qualities were extremely important for assuring minimum levels of performance for this protection. We learned that not all look-alike substitutes are adequate and that a lot more detail goes into these products than much of the public and working population assumed.”
As research revealed that the most likely pathway for transmission was exposure to aerosols — defined by the CDC as a suspension of tiny particles or droplets in the air — the idea that one needed to wipe down groceries and quarantine mail began to fade. It also informed F23’s work on two types of face protection: barrier face coverings and medical masks.
“This recognition of disease pathways, along with other factors, required that the committee redefine some of the test methods and specifications that had previously been standardized,” Stull says. “Simple matters such as having a uniform way of rating filtration properties for any face-worn PPE product (respirators, medical masks, and face coverings) became paramount.”
In the early months of the pandemic there was also much confusion surrounding masks themselves. People were using all sorts of products to try and avoid inhalation of aerosols, from neck gaiters to bandanas, homemade scarves to the ubiquitous blue disposables.
From a standards perspective, it’s useful to understand the difference between the two broad categories of facial protection addressed by F23. Barrier face coverings are defined as a product worn on the face, specifically covering at least the wearer’s nose and mouth, with the primary purpose of providing source control and to provide a degree of particulate filtration to reduce the amount of inhaled particulate matter.
“Barrier face covering is a term that encompasses products that are neither medical face masks nor respirators, and are meant to be more general-use masks,” says Sarah Smit, who is chair of the subcommittee on biological protection (F23.40) and director of laboratory operations for Nelson Laboratories.
A medical face mask, on the other hand, is designed to protect portions of the wearer’s face, including the mucous membrane areas of the wearer’s nose and mouth, from contact with blood and other body fluids during medical procedures. These masks have traditionally been used in hospitals and other healthcare facilities, but in the heat of the pandemic they were lumped in with the many other coverings people were using, blurring the picture regarding which type of protection was best. Not surprisingly, many did not realize that medical masks do not provide inhalation protection.
Source Control vs. Personal Protection
Widespread misconceptions about mask performance were in many ways a reflection of a fundamental misunderstanding of the difference between source control and inhalation protection. Lisa Brosseau, a research consultant who focuses on bioaerosol exposures and respiratory protection and is a member of several F23 subcommittees, explains.
“I think the most important gap we discovered is how little we understand about how well masks, or anything you put on your face, prevent outward leakage of human-generated aerosol, which is known as source control,” she says. Most of the research Brosseau has done in her career has focused on preventing inward leakage — in other words, personal protection.
Once industry professionals began looking more closely at source control, it became apparent that measuring outward leakage of masks was critical to performance evaluation. However, as Brosseau notes, doing so is not easy to accomplish. “We needed a method that would allow us to measure only those particles created by the wearer, inside and outside of the mask,” she says. “Since the air is already full of particles (dust, etc.), current sampling methods will not work. Most of the particles we would measure inside the mask would be those that leak in from the outside environment and almost all of the particles we would measure outside of the mask would be those already present in the ambient environment.”
Stull echoes Brosseau’s comments regarding the need for accurate measurement of the source control provided by devices such as medical masks and barrier face coverings. He also identifies testing that can verify the ability to properly disinfect or decontaminate healthcare PPE products, and ensure that the disinfection process does not compromise their performance — another gap in the standards landscape brought into sharp relief as the pandemic unfolded.
Expansion of mask use from occupational settings, where it was understood to at least some degree, to the day-to-day world of the average person who had little experience with them, highlighted the value of effective communication. “The need to address public needs has been made manifest by our experience with the pandemic,” Stull says, as has the pursuit of product technologies that are more encompassing of disadvantaged and underserved populations. Sustainability was flagged as yet another area that should be taken into account in the development of future PPE standards.
A Better Barrier
As more research was conducted and the on-the-ground experiences of healthcare professionals were examined, it became clear that wearing a face covering was one of the best ways to limit transmission of the virus. The dedicated people who volunteer their time and expertise on ASTM committees were already on the case.
Under the aegis of the subcommittee on respiratory protection (F23.65), development of a new standard specification for barrier face coverings (F3502) was accomplished within an extraordinarily tight time frame, especially considering the fraught environment of an emerging health crisis.
“F23 quickly formed a relatively large workgroup of nearly 100 participants to establish this new standard,” Stull recounts. ”Work was completed within a period of approximately seven months and F3502 was approved through a full ASTM consensus process, something that no other country or region achieved.”
This specification is primarily intended to help ensure that barrier face coverings meeting the stated requirements address both source control for individual wearers (by reducing the number of expelled droplets and aerosols from the wearer’s nose and mouth into the air), and personal protection (by potentially offering a degree of particulate filtration to reduce the amount of such matter inhaled by the wearer).
The standard has quickly become a valuable asset for the many entities involved in trying to combat the pandemic. It has been used by the U.S. government as the basis for purchasing products and is recommended by the Centers for Disease Control (CDC), recognized by the U.S. Food and Drug Administration (FDA), and stipulated as a recommended product specification by the World Health Organization.
Masks and Gowns
The key standard covering medical mask materials was also impacted by the pandemic.
Stull led the project to create the original version of the standard specification for the performance of materials used in medical masks (F2100), which was approved in 2001. “The standard has gone through several changes since then, mainly to tighten test requirements for these products,” he notes. Further revisions have either been completed or are in progress.
According to Smit, key updates to F2100 approved last year include a requirement for ISO 10993 biological evaluation of the finished medical face mask and the addition of a conformity assessment section. Regarding the latter, she points out that the pandemic revealed the need for better quality testing and a way to verify results.
“There is a need to assure testing is performed by competent laboratories,” says Smit. “This revision adds the requirement for the testing to be performed by ISO 17025 accredited labs, an internationally recognized way of establishing confidence in a lab and the results they are producing. The main goal of this revision is assuring the lab can provide consistent and accurate data that complies with the industry standard.”
The subcommittee on biological protection (F23.40), which Smit chairs, is also exploring ways to achieve greater harmony among ASTM mask-related standards. “We’re working on revising the sub-micron test used under F2100 to the same test used for barrier face coverings and respirators,” she says. “Currently, a latex particle challenge is required and has a wide range of parameters that can be chosen that can have a big impact on achieving similar results between labs or manufacturers. The sub-micron test will allow end-users to better compare results.”
Smit adds that a full product standard for medical masks that addresses design features such as fit is on her subcommittee’s agenda.
Although masks have been a major focus of standards-related activity, they are not the only category of PPE to come under scrutiny as the pandemic expanded. The standard specifications for surgical gowns intended for use in healthcare facilities (F2407) and for isolation gowns intended for use in healthcare facilities (F3352) are also in the process of being improved.
“F2407 originated in 2006, while F3352 came into being in 2019, mainly in response to needs defined in the aftermath of Ebola,” Stull explains. “Changes have been proposed to both standards to provide details in how testing should be applied for barrier properties that are not addressed in other industry standards. Additional areas addressed include the identification of relevant physical properties (i.e., strength), alignment of test requirements with historically requested FDA information, and the introduction of a conformity assessment program.”
Each of these items has been subject to multiple ballots since early 2021 as the committee and subcommittees mobilized to address emerging PPE needs.
Stull expects the process of improving the different specifications for general population and healthcare PPE to continue, including development of new test methods to provide complementary metrics that assure proper levels of protection.
“Other areas such as product sizing, cleaning and decontamination, and overall sustainability will also be important new areas to be more extensively investigated and standardized,” he says. “Many of them present difficult challenges because they are relatively broad and have yet to be addressed at any level of detail. However, F23’s membership has grown significantly over the pandemic and there are individuals from around the world who are working to fill existing PPE gaps.”
The willingness of these industry professionals to share their knowledge and experience is making a real difference in the PPE ecosystem. “ASTM offers an open and transparent process that relies on consensus,” says Stull. “F23 has demonstrated its ability to bring resources together in a constructive way to help solve problems for protection needs that have been newly defined. The example of quickly creating a barrier face covering standard that has been adopted globally is evidence that ASTM can be nimble and responsive in creating international standards.”
Brosseau encourages every professional with technical expertise — regardless of their position — to consider contributing to and participating in a consensus standard organization like ASTM. “There is much to be gained both personally and professionally. It gives you the opportunity to see and contribute to something that can have a big influence on the world around you,” she concludes. ■
Jack Maxwell is a freelance writer based in Westmont, N.J.