Before you read any further, take a long, slow, deep breath. Congratulations! If you’re sitting in a typical American home, office building, or school, about 3 percent of the air you breathed in recently came out of the lungs of the people in the room with you right now.
Breathing in one another’s air is kind of nasty when you think about it. We would never drink from the same cup of water that every one of our co-workers had just sipped out of. But something very similar happens all day long in our offices, schools, homes, buses, and even airplanes. All day, every day, we sit around breathing in what other people expel from their lungs. It’s the respiratory equivalent of drinking everyone else’s backwash.
The gross-out factor notwithstanding, inhaling someone else’s breath is not a big deal if they’re not sick. But if they’re actively infectious, they’re constantly releasing viruses packaged in small respiratory aerosols that form deep in the lungs.
How many pathogens you take in depends on one factor in particular: how much fresh air is coming into the building. Most buildings are poorly ventilated. But in a good building—that is, one designed to bring in significantly more outdoor air than building codes in the United States and elsewhere typically require—the proportion of indoor air that comes from other people’s lungs can be brought down to a level at which infection across the room is unlikely.
Throughout the 21st century, employers and commercial-real-estate developers have tried to make workplaces more attractive by adding showy amenities, such as gyms, coffee bars, and beanbag chairs, that supposedly foster creativity and cooperation and keep younger workers happy. Before the coronavirus pandemic, the interior designers and HR professionals who decide how offices look paid little attention to ventilation—an invisible variable that determines whether people can think well at their desk and whether coughs, colds, and other respiratory ills will circulate within a company.
But as companies and their employees ponder what the post-pandemic office will be like, the cool new amenity won’t be a foosball table. It’ll be something we should have had all along—clean air.
I oversee the Healthy Buildings program at Harvard’s public-health school. Our research focuses on how indoor air affects cognition and other aspects of human well-being. (I should note that I also advise businesses, nonprofits, government leaders, and real-estate companies on ventilation and other healthy-building strategies.) In the United States, an engineering guideline known as “acceptable indoor air quality” governs how much air is brought into a building. The problem is right there in the name: I don’t know about you, but I don’t want acceptable air quality; I want good air quality. Instead of being designed to meet a bare-minimum standard, buildings should optimize human health.
The failure to do so landed us in the predicament we are in now: a global pandemic caused by an airborne respiratory virus that spreads almost entirely indoors and has claimed millions of lives around the globe.
Our lack of attention to the air we breathe indoors looks reckless in hindsight. Humanity is now an indoor species. Americans spend 90 percent of our lives indoors. You take 6,000 breaths in your workplace on an average day. Over the past 100 years, humans have made astonishing gains in public health by focusing on the basics of clean water, food safety, and sanitation. But as dozens of my scientific colleagues around the world and I argued recently in the journal Science, governments have not similarly prioritized cleaning up the air that most people breathe most of the time. “In the 21st century,” the article urged, “we need to establish the foundations to ensure the air in our buildings is clean … just as we expect for the water coming out of our taps.”
As a basic toxicology rule asserts, the dose makes the poison. By reducing the dose of coronavirus that people inhaled, higher levels of ventilation and filtration could have kept a lot of indoor spread of COVID-19 at bay. Yet with the exception of hospitals, most buildings were not designed to limit the spread of infectious diseases. Instead, architects in recent decades have designed buildings, and their owners have operated them, with the goal of making them airtight. This mindset has helped with energy efficiency, but it has the distinct downside of concentrating indoor pollutants—not only those from our lungs but also the chemicals emanating from chairs, carpets, cleaning agents, and personal-care products. As a result, we were living and working in a sick-building era even before the coronavirus arrived.
That era is coming to an end. COVID-19 has prompted a universal awakening about the power of our buildings to make us sick or keep us well. At this point, really, who wants to go back to a building that isn’t healthy?
The good news is that every building can improve. Cars need tune-ups; so do buildings. Frequent inspections reveal missing filters, closed dampers, and malfunctioning fans. Over time, older HVAC equipment can be replaced with newer, more powerful, more energy-efficient technology. These upgrades will involve some expense, but building owners and their tenants will get a higher return from them than from gimmicky office furnishings—and not just because better air quality protects workers from COVID-19.
My team at Harvard recently published research on the health of several hundred office workers around the world for more than a year. We found that people performed better on cognition tests when the ventilation rate in their working environment was higher. When they were exposed to more outdoor air, they responded to questions more quickly and got more answers right.
Our team reached a similar finding a few years back in a tightly controlled laboratory setting. In that study, people did notably better on cognitive tasks when carbon dioxide made up about 600 parts per million of the air they breathed than when it made up about 1,000 parts per million. (CO2 indoors comes primarily from human exhalation and therefore makes a useful proxy measure; the lower the CO2 level, the better the ventilation.) In our new research, we observed the effect in real buildings globally. We also observed a reduction of worker performance even at indoor CO2 levels that many researchers had previously assumed were perfectly fine.
Our recent research also looked at how short-term exposure to a category of small airborne particulates called PM2.5 affected human cognitive function. PM2.5—the name refers to particulate matter less than 2.5 microns in diameter—comes from sources such as power plants, cars, and wildfires and is typically considered an outdoor pollutant. But outdoor air pollutants penetrate indoors. And because Americans tend to breathe more air indoors than out, we counterintuitively breathe more outdoor air pollution indoors than we do outside. PM2.5 was already known to cause cardiovascular disease and asthma attacks. Our study found that less indoor exposure to the pollutant was also associated with quicker response times on cognitive-function tests.
Some of these findings might seem contradictory: Bringing in more outdoor air should be good for cognition, but outdoor air is polluted with particles that hurt cognition. This is where better filtering comes in. We found that buildings with high levels of filtration had about 40 percent less PM2.5 indoors. By capturing pollutants before people inside have to breathe them, buildings can give people the benefits of outdoor air without the downside. Healthy buildings improve your well-being and cognition while also protecting you against outdoor pollutants and infectious diseases.
In the past, a layperson could not easily tell how well a building was ventilated. Assessing a room’s carbon-dioxide level, for example, used to require a scientific instrument. But you can now buy a good CO2 monitor for about $200. Citizen scientists can easily find out when an occupied space barely meets the acceptable-air-quality standard—or even falls short of it—and will share those results on social media.
Beyond helping end the pandemic, better ventilation and filtration will make everyone healthier and more productive. Once constructed, buildings are slow to change, as owners put off upgrades that will yield long-term gains. But COVID-19 will prompt people to ask more questions about their workplaces—and will force the hand of employers and building owners. Foosball tables are no longer enough. The world finally has to pay attention to indoor air.