Whether we like it or not, the COVID-19 pandemic has forced every building professional to learn about infection control. Once a consideration limited to health care facilities, reducing the infectivity of the indoor environment is now the No. 1 concern in every occupied building. This priority even trumps energy conservation as demonstrated by recommendations for maximum ventilation rates irrespective of the outdoor temperature.
Airborne transmission of SARS-CoV-2, including distances over a 6-foot limit, has now been deemed the most influential transmission route by the U.S. Centers for Disease Control and Prevention (CDC). Engineers and building managers now have the opportunity and responsibility to save lives by decreasing virus exposure in breathing zones. The opportunity goes beyond COVID-19.
We now know that many diseases can be prevented or decreased by limiting indoor exposure to particulate matter, organic gases (hydrogen and carbon chains), inorganic gases, and low ambient relative humidity. For example, we now know that inhaling fine particles increases heart disease, strokes, and can even trigger premature birth. Water-soluble gases mix with our respiratory tract mucus to gain access to our tissues, while non-polar gases can diffuse directly through our cell walls and cause organ damage. Ambient air with low relative humidity (RH) causes increased reactivity and inflammation in cells lining our bronchial tubes as well as other problems from even mild tissue dehydration.
Furthermore, harm from pollutant and adverse thermal conditions does not require days or even hours of exposure. In some cases, damage begins after several minutes. While some of us voluntarily ingest harmful molecules if we choose to smoke or drink excessive volumes of alcohol, all of us can be involuntary toxin–ingestors when they are non-detectible in the indoor air surrounding us.
The added dimension of protecting health requires that engineers understand that indoor exposures are only one half of the equation. The other half is understanding the direct impact of indoor conditions on occupant immunity and overall health.
On closer inspection of the list, monitoring air quality is more straightforward than quantifying the health consequences of exposures because health impact involves variables that can be difficult to capture. These often elusive variables are occupant age, activity levels, liver function and its ability to detoxify chemicals, and other underlying states of health or disease. Furthermore, indoor exposures can combine to become more impactful than individual compounds. For example, when indoor RH is less than 40%, inhaled particles can gain deeper entry into lungs and cause greater damage than the same particles in the healthy RH 40%-60% zone.
ASHRAE states, “Engineers are better able to keep indoor environments safe and productive while protecting and preserving the outdoors.” To fulfill the promise for safety, building professionals must understand not only how to decrease indoor pollutants but also understand how indoor conditions impact occupant immunity and general health. Despite the complexity, we must at least not confuse air quality measurements and the health impact of the indoor environment.
Clearly, the human body does not exist in a silo. Our cells, tissues, and organs interact with and are impacted by our environment. I am confident building professionals will embrace the opportunity to save lives as we fight COVID-19 and all infectious diseases that are transmitted through the indoor environment.