How Does “No Mask Required” Affect Air Quality and Risk Mitigation Strategies

16 June 2021 | Wednesday | Opinion | By Behind The Bench Staff | ThermoFisher

Public health guidance issued in mid-May from the White House.1 said fully vaccinated people no longer need to wear a mask or physically distance in any setting, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance.

Can owners and managers of local businesses and workplaces breathe a sigh of relief that they don’t need to worry about Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) affecting their employees, customers, and businesses anymore? Although many news articles are reporting that SARS-CoV-2 cases are down, those who manage risk mitigation strategies and programs for their companies may be conflicted about the new mask rules.

One reason is that the Association of American Medical Colleges2 reported that COVID-19 variants are spreading rapidly.  Faster vaccination offers one of the best chances to avoid another deadly surge, but the CDC’s data tracker3 reports that as of mid-May, 2021, only about 46.6% of the total U.S. population has received at least one dose of vaccine, and about 35.8% of the total U.S. population has been fully vaccinated.

While the vaccine itself cannot give you the virus, it is also not 100% effective at preventing the virus entirely. Daniel C. DeSimone, M.D of the Mayo Clinic4 recently wrote: “Keep in mind that if you’re fully vaccinated, your risk of getting COVID-19 might be low. But if you become infected, you might spread the disease to others even if you don’t have signs or symptoms of COVID-19. This could be dangerous for people who are unvaccinated and at increased risk of severe illness from COVID-19.”

Virus Can Linger in the Air

The Johns Hopkins Bloomberg School of Public Health5 has reported that there is evidence that points towards the “likelihood that the virus may be spread through aerosols that linger, not just droplets that fall.”

An Environmental International June 2021 article6 notes that “… infection can be caused by inhalation of small droplets exhaled by an infected person that can travel distance of meters or tens of meters in the air and carry their viral content. Science explains the mechanisms of such transport and there is evidence that this is a significant route of infection in indoor environments.”

The article goes on to note that “A World Health Organization (WHO 2009)7 review of the evidence stated that viral infectious diseases can be transmitted across distances relevant to indoor environments by aerosols (e.g. airborne infections), and can result in large clusters of infection in a short period.”

How can workplaces — including hospitals, schools, public buildings, and businesses – reduce the risk of being a ‘spreader’ location while the public leans toward no mask wearing and half the population have not yet received vaccines?  Some organizations are incorporating environmental surveillance to complement their other risk mitigation strategies.

Environmental surveillance, which can include surface swabbing, wastewater testing, and air sampling strategies, can produce information that can help guide and strengthen safety protocols to help prevent virus spread.  In the article Perspectives in Medical Virology8, the authors write: “Surveillance is a fundamental tool for public health, producing information to guide actions. In the context of newly emerging viruses, surveillance may be performed to detect disease outbreaks, to monitor the spread or development of ongoing outbreaks, to evaluate the effectiveness of disease control measures, or to identify the determinants of infection and disease.”

Surface Swabbing

In 2020, Australia’s National Science Agency (CSIRO)9 studied how long the virus survives on common surfaces (including stainless steel, glass, paper, cotton cloth) at different temperatures. Their conclusion: “While the main method of spread of SARS-CoV-2 is via aerosols and respiratory droplets, our results indicate that high-contact surfaces may pose a risk. However, viruses do not penetrate skin and to transfer the virus from a surface requires that a person introduce it into their mouth, nose or eyes.”

At the beginning of 2021, Chemical Engineering News10 reported that surface swabbing helped researchers get a handle on COVID-19 cases. According to the article, over a three-month period, a Tufts University environmental health research group collected weekly swab samples from crosswalk buttons, garbage can handles, ATM machines and other high-touch surfaces throughout a densely populated city outside Boston.  The researchers watched locations, swabbed them, recorded the number of touches, noted mask wearing, and took the samples back to the lab for measurement of viral RNA using the quantitative reverse-transcription polymerase chain reaction method. They then used public health records to track the rise and fall of COVID-19 cases in the city over the same time period. The results: “They found that levels of viral RNA on high-touch surfaces offered a reasonable prediction of case trends in the community 7 days later, potentially providing a useful surveillance tool that could help public health authorities to anticipate outbreaks and take action to stop them.”

Wastewater Testing

Wastewater testing refers to the collection of rainwater and expended water from households and industries (i.e., from toilets, showers, sinks) that can contain human fecal waste, which is then tested for RNA from SARS-CoV-2.

In a short video11 from the University of Washington Civil & Environmental Engineering department, a research technician shows how wastewater is collected from manholes and neighborhood pump stations, and how these samples are tested and can indicate if there are outbreaks in particular communities. Mari Winkler, an Assistant Professor at the university, believes that this testing is like a smoke detector… it can determine ‘where the fire is burning’ and where there is an upward (or downward) trend.

The CDC12 notes, however, that although sewage surveillance can be an indicator, at this time, it is not possible to reliably and accurately predict the number of infected individuals in a community.

Air Sampling (In-Air Pathogen Surveillance)

Air sampling is not new technology, but it is a new application in the battle against SARS- CoV-2. In-air pathogen surveillance solutions can deliver data about the presence (or absence) of pathogens in indoor air—so one can identify risks and make faster, more reliable, and more confident decisions about the ability to safely re-open a facility and stay open.

In-air pathogen surveillance starts with an instrument that collects air samples and captures aerosols the size of a virus on a cartridge collection substrate. The air samples are then sent to a laboratory for polymerase chain reaction (PCR) testing to determine the presence of RNA from SARS-CoV-2.  PCR tests for the presence of the actual virus’s genetic material or its fragments as it breaks down.

Recently, a  group at the University of Oregon investigated the effectiveness of integrated surveillance using an active air sampler13, surface swabs and passive settling plates to detect SARS-CoV-2 in hospital rooms with COVID-19 patients and compared detection efficacy among sampling methods.

In room-scale aerosol experiments, consistent detection of aerosol SARS-CoV-2 was achieved at a concentration equal to or greater than 0.089 genome copies per liter of room air (gc/L) when air was sampled for eight hours or more at less than one air change per hour (ACH). Shorter sampling periods (~75 minutes) yielded consistent detection at ~31.8 gc/L of room air and intermittent detection down to ~0.318 gc/L at (1 and 6+ ACH respectively). These results suggest the utility of indoor aerosol surveillance as an effective risk mitigation strategy in occupied buildings. (Read Evaluation of a Bioaerosol Sampler for Indoor Environmental Surveillance of Severe Acute Respiratory Syndrome Coronavirus 214)


Even as the country moves from pandemic to a post-pandemic strategies, it make sense to continue performing environmental surveillance for in-air pathogens in select environments in conjunction with other risk mitigation strategies.

For environmental and occupational surveillance, the goal is to provide additional insights to individualized testing and to help assess the safety processes and controls within the facilities. As noted by the CDC12 and in the Chemical Engineering News10article mentioned above, wastewater collection and surface swabbing can offer some guidance for large populations, but can take more time and offer less targeted data than air sampling technology.  In-air surveillance tools used in specific areas can provide more timely and highly reliable insight into in-air pathogen presence so one can monitor and improve building and facility safety protocols.

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