Take your age and multiply it by 0.9. That’s your indoor age, or the number of years that you’ve spent inside your home or office, according to Joseph G. Allen, director of the healthy buildings program at Harvard’s T. H. Chan School of Public Health. For most people, it’s equal to about 90% of their life.
These days, the amount of time people spend indoors is likely closer to 100%. Covid-19 has forced us indoors in an unprecedented shift in the way we live, work, and love. In many parts of the world, the pandemic has meant no more commutes, travel, weddings, or team sports—the activities that used to make up the 10% of our lives we spent outdoors are mostly gone.
That shift has sparked an awakening in how we view our indoor environments. Covid-19 is an airborne disease, and one of the main takeaways of the last year is that ventilation saves lives. But what’s in our indoor air affects our health beyond Covid. In fact, the quality of our air has a disproportionate effect on our physical and mental well-being—so much so, argues Allen, that our building managers have a greater impact on our health than our doctors.
Past pandemics and decades of research have transformed the way in which engineers and architects understand how the built environment affects our health. But the way we build our homes and our offices hasn’t evolved in tandem with the science, in part because of what many experts consider to be a false dichotomy between energy efficiency and healthy buildings—the idea that if you let a building breathe, you will waste energy, which is more expensive for the consumer and bad for the environment.
Now, with the twin crises of Covid-19 and climate change, it’s clear that buildings—the places where we spend most of our time—are not fit for purpose. But they can become tools to help us lead healthier lives. That starts with cleaning up the air we breathe indoors.
Experts know that crises can create windows of opportunity for action, but they also know that those windows are short-lived. “There is certainly a peak of interest” in indoor air pollution because of Covid-19, says Jose-Luis Jimenez, a professor of chemistry at the University of Colorado Boulder. “It will go down; we just don’t want it to go down to zero.”
The “dirty secret” of outdoor air pollutants is that most of our exposure to them actually happens indoors, according to “Healthy Buildings: How indoor spaces drive performance and productivity,” a book that Allen co-authored with John Macomber, a senior lecturer at Harvard Business School. “People who have been working in indoor air pollution for years, like me,” explains Nicola Carslaw, a professor of indoor air chemistry at the University of York, “have always felt that indoors is ignored” by policymakers, the public, and even the broader scientific community, which for a long time was more focused on outdoor air pollution.
Air is made up of particles and gases that interact with each other. Indoor air pollutants can come from outdoors, from our stuff, from our buildings, or from us—the things we do or products we put on our bodies. Studies show that, under normal conditions, an estimated 50% of outdoor air infiltrates the median American home. That means common and dangerous pollutants like particulate matter are floating around indoors, too. These can come from human or natural sources such as power plants, cars, or plants (pollen), but their size is what makes them dangerous: They are smaller than 2.5 microns or 10 microns (hence the names PM2.5 or PM10), can get into the lungs and bloodstream through the respiratory tract, and cause health problems.
We also generate pollutants by simply existing indoors. Some of the more common are volatile organic compounds (VOCs), which can emanate from furniture, cleaning products, and building materials. These compounds can be harmful to our health on their own and they can also interact with each other and the people in a room in ways that harm us; an example that Allen and Macomber use in their book is limonene, a chemical that is added to cleaning products for its smell, but that reacts with the ozone that occurs naturally in air to form formaldehyde, which can cause cancer. And even if we don’t generate these pollutants in our homes, they can waft in from neighboring buildings or other parts of our buildings.
The sum of the particles and gases in our air make up our indoor air quality, or IAQ, and they affect each of us very differently, according to Lisa Ng, an indoor air quality expert at the National Institute of Standards and Technology (NIST), a US government agency. That’s why “there is no one metric to say what is ‘good’ or ‘bad’ indoor air quality.” Everyone is impacted by PM2.5 but asthmatics, for example, will be more sensitive to its effects than others. Still “there is a general agreement that the more we can lower these levels indoors the better,” Ng says, “because there are reactions that happen between chemicals and particulates that we don’t even understand yet.”
Long-term exposure to high levels of particulate matter is associated with higher rates of:
- Hospital admissions
- Death from heart attacks and strokes
- Death from respiratory diseases
- Lung cancer
- Asthma (and more severe asthma for those who already have it)
- In fetuses, premature birth and low birth weight, which in turn is linked to chronic diseases of the body, brain, and nervous system in adults
You might think that air pollution would be a great equalizer; no matter how rich you are, you still have to breathe. But in many countries—though not all—both indoor and outdoor air pollution disproportionately affect the poor and marginalized, who are more likely to live in densely-populated areas and poorly-ventilated homes near busy roads (where nitrogen dioxide emitted from cars can waft into houses through open windows).
Indoor air pollution is also a problem that affects more poor countries than rich ones: In 2016, according to the World Health Organization (WHO), the air in 98% of large cities in low- and middle-income countries exceeded its outdoor PM2.5 guidelines, compared to 56% of large cities in high-income countries. The 15 most polluted cities in the world are all in India or China.
Covid-19 is not the first pandemic, nor will it be the last.
In the late 19th and early 20th century, influenza killed 22 to 58 million people. Most of those died of the Spanish flu of 1918. There were also major outbreaks of diseases like cholera and tuberculosis, as well as wars.
Visionaries like Florence Nightingale knew that sick patients would benefit from fresh air, sunlight, space, and hygiene. Working with wounded soldiers in Crimea in 1854, Nightingale was able to reduce the mortality rate in one hospital from 40% to 2% by spacing out the beds, opening windows, and sanitizing the space. She later developed guidelines that influenced how post-war British hospitals were built. Among other things, she called for more distance between beds and for hospital gardens to grow medicinal herbs and allow patients to exercise.
Infectious disease prevention was a priority for 20th century modernist architects. In his 1931 book Towards a New Architecture, Swiss-French architect Le Corbusier described an ideal modernist home as having a kitchen positioned so that cooking smells wouldn’t spread throughout the house, ample ventilation and windows in every room, and no thick carpets or heavy furniture. “A house is only habitable when it is full of light and air, and when the floors and walls are clear,” he wrote.
“Then we lost our way,” laments Harvard’s Allen. In the 1950s, engineers began using cheaper and more industrial materials in buildings, some of which scientists have now discovered are toxic. After fluorescent lighting was invented, architects started to rely on it to bring light into people’s homes and offices, instead of using the building’s architecture (what’s known as passive design), creating a sealed-off indoor environment.
The invention of air conditioning had a more mixed track record: It made life bearable for people who live in overheated places, and central mechanical ventilation filters and distributes air throughout a building. But air conditioning uses carbon-emitting fossil fuels to generate electricity: According to the US-based Climate Institute, roughly “20% of the total electricity used in buildings around the world goes towards air conditioners and electric fans,” and that is expected to triple by 2050 as a growing middle class in poor countries becomes more able to afford AC.
When the 1973 oil embargo brought an end to cheap energy, “a whole generation [of designers] had lost that skill” of passive design, says Kevin Van Den Wymelenberg, the founder of the Institute for Health in the Built Environment at the University of Oregon. Instead of taking advantage of a building’s orientation or proximity to greenery in order to save energy, “we started tightening up our building envelopes and lowering the amount of fresh air that comes in in an effort to conserve energy,” Allen explains.
By the 1980s, says Van Den Wymelenberg, “we designed buildings completely around esthetic exterior expression and whatever happened on the inside was irrelevant.” That’s when the term “sick building syndrome” entered the lexicon—the idea that spending too much time in open-plan offices in air-tight buildings with no natural light can make you feel sick. “For the past 40 years, we’ve designed our buildings to not bring in enough air and not use good filters,” argues Allen, “We knew it was a problem before Covid-19.”
Not only were buildings making us sick, they were contributing to climate change: According to Allen and Macomber, “buildings represent the largest consumers of materials of all industries on Earth.” Experts who realized this created the green building movement of the late 1990s, whose goal was to “promote sustainability in the building and construction industries.” The first formal institution of this movement was the US Green Building Council (USGBC), formed in 1993, and later expanded to other countries in 1998 as World GBC.
By the 2010s, it became clear that making buildings sustainable wasn’t enough. “As we continue to meet the market demands of today, we must also begin responding to the market demands of tomorrow,” USGBC executive Mahesh Ramanujam said at a conference in Beijing in 2014. “Indeed, a new market is emerging for which we all must be at the ready: buildings that promote human health.”
The green building movement transitioned into the healthy buildings movement to promote the idea that buildings can become tools to fight pandemics and to improve both our well-being and our productivity—and that this can be done in ways that minimize the impact they have on climate change. The foundational principles of a healthy building include aspects relevant to indoor air like ventilation and moisture, but go beyond it to look at health holistically, placing value on elements like lighting, noise, water quality, and safety.
At its heart, the healthy buildings movement is calling for a return to the basic principles of modernist architecture: Let light and air in, ventilate, and minimize indoor and outdoor sources of pollutants. “Perimeter ventilation through a window and daylight is the gold standard,” says Mark Fretz, associate director of outreach at the University of Oregon’s Institute for Health in the Built Environment.
It might seem like those principles are incompatible with the goal of tackling climate change. But today, architects can design buildings that are friendly to both the environment and human health. “There’s a widespread perception that if you improve air quality or any other aspect of indoor environmental quality, you’re going to increase energy use and cut against goals of zero emission, zero energy use buildings,” says William Bahnfleth, a professor of architectural engineering at the Pennsylvania State University. “I don’t believe that.”
An efficient heating and cooling system, equipped with a filter designed to trap fine particles, is key. Companies are working to develop more accurate and cheaper IAQ sensors that can control this system to better suit the people occupying the space. “If we design systems to identify where there are people, then they can control temperature and humidity and the amount of outdoor air that’s delivered to those locations and… that can create huge energy savings,” Bahnfleth argues. Having a unit with a fan and a high-efficiency filter that is routinely checked and replaced can make a huge difference.
The pandemics of the past 100 years revolutionized building design, and Covid-19 could do it too, says the University of Oregon’s Van Den Wymelenberg. That starts with designing buildings with good ventilation systems, that are connected to nature, that don’t waste energy but let in air and light, and that make people healthier, not sicker—and doing it equitably, so that clean air doesn’t become one more thing that gives the rich a leg up over the poor. “My vision, my dream, my hope for the future of buildings is that we design with intention for health, energy, and community,” he says. “We’ve got to do better.”
Short of waiting for the effects of the pandemic to trickle down into architectural design and building codes, there are things you can do right now to improve your air quality, says Ng. These involve pulling three main levers: You, your space, and your building.
“The primary indoor pollutant is people,” says Van Den Wymelenberg. “Everything that we breathe out, everything that we exhaust, that sheds off our skin, all the skin care products that we put on our body—all of those things sloughed off into the built environment.” To that we’ll add: everything you do in your home or your office, including cooking, smoking, cleaning, or just existing. “The key is to avoid fragrance products where you don’t need them, and when you’re cleaning or cooking, to ventilate,” says the University of York’s Carslaw. “If everybody did that it would solve a lot of issues.”
Teaching people about the common sense ways in which they can reduce their exposure to pollutants at home or in the office requires an understanding of human behavior—why it is, for example, that most of us don’t turn our range hoods on when we cook (pdf, p. 7). “If you don’t understand how people use their homes,” she adds, “it doesn’t matter how much you understand about the chemistry, it’s a waste of time.”
Another major source of indoor air pollution is furniture and the materials we use to build our homes and offices. New furniture “off-gasses” more chemicals, so Carslaw recommends investing in second-hand furniture, unless the latter was owned by a smoker (in which case, beware of the effects of third-hand smoke). An easy rule of thumb is to dust and clean your space regularly and avoid things that collect and store particles, like carpets. Finally, some people with respiratory conditions or who live in particularly polluted areas might want to invest in air purifiers for their homes, but experts say they should make sure the device is equipped with a HEPA filter that they regularly clean and change.
Your building is one of the toughest levers to pull because, short of moving to a different address, there’s not much you can do if your landlord or property manager isn’t being cooperative. Allen and Macomber recommend getting your building’s ventilation system and the quality of the air and the water in your home tested regularly by a technician. If your building is mechanically ventilated—that is, uses a filter to remove particles—they suggest upgrading the filter to a higher value, and increasing the ventilation rate of your building.
Covid-19 could be the crisis that leads to systemic change in indoor air pollution, says the University of Colorado Boulder’s Jimenez. But there’s also a real risk that this change won’t be equitable and will instead further entrench socioeconomic inequalities that exacerbate climate change and pandemics.
Some solutions are cheap and effective. The University of York’s Carslaw points to India, where many women cook indoors using solid fuels like coal that can cause lung cancer. “You need a $5 cooker hood in most homes and the problem is solved, for indoors anyway,” she says. Some solutions are more expensive but worth considering given the costs of inaction. Ng believes US states should invest in better filters for every public school. “Unfortunately, the state of the US school system is that there is a lot of disparity and some schools aren’t able to even buy textbooks, let alone buy upgraded filters.”
“Why is it acceptable to have our children and the people who take care of them in schools breathe bad air?” asks Paula Olsiewski, a biochemist and contributing scholar at the Johns Hopkins Center for Health Security. She believes health insurance companies should reimburse people for buying portable air cleaners the same way they would cover people’s inhalers or insulin—because dirty air is making us sick like our underlying conditions, and worsening those to boot. “You can buy the $800 [air purifier] that has bells and whistles and [measures] this and the other things, but you can also buy one for $150, or you can make one,” she adds.
As the problem of air pollution has worsened worldwide, companies have stepped into the gap left by governments and regulators in order to sell us products that allegedly make our air cleaner. Some of it works, but there’s also “lots of snake oil stuff,” says Carslaw, “that at best is doing nothing but at worst is making things worse.”
For example, for the modest price of $125, one company will sell you 580 ml of fresh air “farmed” from the British countryside using a net. (Yes, that’s a true story.) Another company sells 8 liter tubes of air collected from six locations in Switzerland for about $20. Some market it specifically as an antidote to air pollution, others as a way to fix homesickness—a company called My Baggage advertises bottles of “authentic air from the London Underground, fish and chips aroma from Norfolk, and fresh mist from the summit of Snowdonia,” while Etsy has an entire canned air section.
To be clear, though no studies have proven that breathing cans of air improves or harms your health, there’s also no evidence that it works. And while it’s easy to dismiss canned air as a joke, the truth is that if the air we breathe wasn’t so polluted, there probably wouldn’t be a market for it.
The next frontier for change will take place with standard-setting bodies and regulators, who have focused on outdoor air pollution for so long that, until recently, they virtually ignored the indoor space. “There was this enormous imbalance that even though we spent all this time indoors, all the chemical measurements were developed for outdoors,” says Jimenez.
In the US, there is no national indoor air quality standard, but the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), a professional organization, developed guidelines known as standard 62.1 that are widely referenced in building codes, according to Bahnfleth. Some argue it doesn’t go far enough; in their book, Allen and Macomber recommend increasing buildings’s ventilation rates from the “acceptable minimum” set out by ASHRAE of about 20 cubic feet per minute (cfm) per person to at least 30 cfm per person.
Both the green and healthy building movements have organizations that inspect and certify buildings according to their standards. They include the Indian Green Building Council, the US-based International WELL Building Institute and its WELL Building Standard, or RESET, a sensor-based standard developed in China. These organizations are helping disseminate the science of healthy buildings around the world: The US Centers for Disease Control and Prevention’s Fitwel certification system, for example, has an Asian advisory council. Since some of the world’s most polluted air can be found in the Global South, those countries should be a priority for the movement, as well as research into how buildings can best serve women and people of “races and ethnicities that have been historically under-represented in research,” writes Allen.
Since outdoor air quality impacts indoor air quality, Bahnfleth believes it should be taken into account in regional building and construction standards. A building in Bangor, Maine, one of the cleanest metropolitan areas in the US, may need a different HVAC system than one in Los Angeles in the middle of last year’s wildfires. And Jimenez suggests that restaurants, bars, and other public spaces should display indoor air quality readers to let patrons know what kind of air they’re breathing, the same way New York City’s letter grading system lets them know if the restaurant is sanitary. “You can only improve what you measure,” he says.
Of course, any action taken to improve outdoor air pollution, such as stricter regulation or greater adoption of electric vehicles, will have a beneficial impact on indoor air pollution too, because “as we pollute the outdoor air, we are polluting our indoor air,” says Ng.
Our homes and offices can do more than help us avoid disease; they can make us healthier. Allen feels “a real responsibility right now to help get this message out and help shape what comes next so we don’t revert back to the sick building era.”
Whatever happens, Covid-19 is shaping up to be an inflection point for indoor air pollution, says Olsiewski. “I think we’re just at the beginning.”