One of the unexpected benefits of the pandemic has been the improvement of outdoor air quality. When stay-at-home measures first went into effect last spring, they resulted in a measurable drop in common air pollutants like nitrogen dioxide. According to the Center for Research on Energy and Clean Air, NO2 levels declined by 27% after municipalities adopted such measures, and harmful particles under 2.5 micrometers in diameter (PM2.5) dropped by 5%.
Now that mobility restrictions have eased, air pollution has unfortunately returned to near pre-COVID-19 levels. Nevertheless, this period of decreased pollution during the pandemic has brought increased scrutiny to the harmful effects of dirty air. For example, CREA calculates that 4,600 deaths were avoided in Delhi, one of the world’s most polluted cities, due to the coronavirus lock-down. Approximately the same number of Delhi residents died from coronavirus-related complications during the same period.
So far, COVID-19 has claimed nearly 1 million lives worldwide. Meanwhile, air pollution is responsible for 7 million deaths annually. According to the World Health Organization, only one in 10 people worldwide breathe air that meets WHO’s recommended quality guidelines. Although wildfires and vehicles have attracted much of the recent blame for dirty air, buildings comprise a significant part of the problem. According to the World Green Building Council, “the contribution of the built environment [to air pollution], in both the construction and operational phases, cannot be underestimated.”
Of the nearly 40% of global CO2 missions that buildings contribute, 28% is associated with building operations while the remainder is attributed to building construction. Fuel-related emissions also include PM2.5 and PM10 particles, and construction dust (from materials like concrete, wood, or silica) represents a significant source of PM10 pollution. Returning to the example of Delhi: A 2016 report indicated that construction dust comprises 30% of air pollution in the city. According to Anti Toxic Watch Alliance environmentalist Gopal Krishna: “The construction sites are full of ultrafine, nanofine, silica, and asbestos particles, which are very tiny and cause respiratory diseases among workers and others who are under the exposure.” If construction contributes nearly a third of Delhi's air pollution, it stands to reason that it is also a major cause of the pollution-related illnesses and deaths there.
During the current pandemic, poor air quality may also be intensifying the public health crisis. The CREA mortality figures cited above consider COVID-19 and air pollution data separately. However, a recent Harvard study determined that dirty air exacerbates the coronavirus' effects, particularly for those with long-term exposure to air pollution. The nationwide survey of U.S. COVID-19 mortality levels concluded that “an increase of 1 μg/m3 in PM2.5 is associated with an 8% increase in the COVID-19 death rate.” To put that number in perspective, the average concentration of PM2.5 in Delhi is nearly 100 μg/m3.
Closing the windows and staying inside isn't necessarily a solution. Poor indoor air quality can also intensify the coronavirus's deleterious effects. According to a study in the Journal of Exposure Science & Environmental Epidemiology, “3.8 million people worldwide prematurely die from illnesses attributable to indoor air," and dirty household air has “even greater relevance now that many individuals are spending more time at home.”
Given that we normally spend as much as 90% of our time indoors, that is where most of our exposure to air pollution occurs. Interior environments are characterized by their own distinctive forms of pollution that are generated by reactive chemicals found in construction materials, furnishings, paint, furniture, cleaning agents, combustion appliances, and other substances. These materials emit unsaturated, nitrated, and oxygenated volatile organic compounds as well as secondary ozonides and secondary organic aerosols. The trend towards making buildings airtight, thereby reducing fresh air recharge rates, has intensified the presence of these and other “stealth pollutants.”
Notably, the adverse influence indoor pollutants have on COVID-19 sufferers undermines the fundamental logic of public health protocols. The strategy of isolating infected individuals in their homes is based on the idea that the reduced likelihood of transmission will ease the burden on the healthcare system. Yet because common indoor pollutants exacerbate the virus's effects, infected individuals may have a greater need for medical attention due to the poor air quality in some home environments. As the authors argue in that Journal of Exposure Science & Environmental Epidemiology article, “society fails to gain the full benefits of stay-at-home orders because the healthcare system is utilized regardless, and those most at-risk for COVID-19 complications are also placed at greater risk of exposure.”
In these ways, the built environment plays a more vital role in public health than conventionally understood. Polluted air generated from building construction, operation, and indoor material chemistry remains a crucial problem—one that is thwarting our attempts to fight the pandemic. If we have learned a consequential lesson from COVID-19, it is that architecture must make clean air a fundamental priority.
