Your Turn: We need to stop overlooking ventilation and filtration
Douglas County has done better than several surrounding counties relative to many of the COVID-19 indicators. More consistent mask wearing is likely part of the underlying reason for this; at least many of our local public health officials think so. And there’s certainly data to back up the benefits of mask wearing, including the CDC’s recent study making use of Kansas data.
Masks are a critical part of a successful layered approach for reducing the risk of infection. They are in essence wearable filters sitting against your nose and mouth, capturing virus-containing aerosols as they leave an infected person or before being inhaled by a noninfected individual.
The same basic principle underlies building system filtration and portable HEPA filter units, two key strategies for removing virus-containing aerosols indoors. Another key strategy is ventilation: the introduction of outdoor air into a space either via the building’s mechanical system or naturally from opening windows. Ventilation dilutes virus concentration levels, making it less likely enough particles are inhaled to result in an infection.
Strategically combined with building exhaust, ventilation and filtration strategies have been shown, both empirically and through modeling, to significantly reduce the risk of infection from pathogens indoors via aerosols, including the coronavirus. Aerosol researchers, infection control specialists and building scientists have been promoting these building-focused strategies since last spring as part of a comprehensive layered approach for reducing risk.
Yet due to the WHO’s and CDC’s delay in recognizing the importance of transmission via aerosols, both awareness and guidance have been lacking from state and county health departments, including our own. This has resulted in indoor environments less safe than they should be, contributing to the spread of the virus, including super-spreading events.
Many of these experts have been frustrated at the lack of response from state and local public health officials when presented with this information. I’ve experienced it myself. But with threats to their lives and livelihood from simply trying to fulfill their job description, a lack of federal support and leadership, a weak and inconsistent CDC until as of late, and direct GOP efforts to sabotage their efforts, it’s not hard to see why they’ve struggled with this issue (and others).
And with vaccine distribution now on their plate, I’m less than hopeful they’ll have the bandwidth to address this, which is unfortunate because over the next six-plus months, as we stumble through vaccination, as people chomp at the bit to return to socializing, to traveling, to congregating in large groups indoors, with continued if not increasing lapses in judgment, we will need all of the layered approaches in place. And that includes ventilation and filtration.
The CDC has finally issued guidance on this. Hopefully, state and county health departments will prominently include this information on their websites. But we also need informative and easy to understand graphics for communicating this in a variety of settings, from homes to schools to businesses (such as this).
Public health officials could also promote the use of risk estimators, like the one I helped develop, to establish varying combinations of the maximum number of occupants, maximum exposure time, limits on singing, activities requiring high exertion, etc., relative to a building’s existing ventilation and filtration characteristics (taking mask wearing and community infection rates into account).
Such efforts would help verify and communicate the relative safety of different buildings, help prioritize activities at a local level and potentially help increase public confidence in local pandemic response measures. Better accounting of the indoor threat from virus-containing aerosols would further reduce risk, save more lives and likely allow more activity to occur sooner as vaccination levels ramp up (including in-person school). It would help build the bridge to the vaccination levels needed.
Not only that, but these measures also increase health and wellness overall — something that will be an important consideration in our approaching post-pandemic world as we also strive to reduce the greenhouse gas emissions produced by our built environments.
— Marcel Harmon, an anthropologist, engineer, and former Lawrence school board member, leads the R&D services of a high performance building consulting firm, and has led projects to assess the risk of viral infections within buildings.