To Make a Building Healthier, Stop Sanitizing Everything
Improve the ventilation, even spread some good germs. If you
want people to be healthy and productive, tend the microbiome.
Four years ago a doctoral student in architecture asked Luke Leung to help him come up with a
thesis topic. Leung, an engineer whose projects include the world’s tallest
building, the Burj Khalifa in Dubai, proposed the question: What is heaven?
“The student did a lot of research and found that no matter
the faith—Islam, Judaism, Christianity—heaven is always a place with a garden
and running water,” recalls Leung, director of the sustainable engineering
studio of Skidmore Owings & Merrill, the architectural behemoth better
known as SOM. “So then we started questioning, ‘If that is heaven, what exactly
is the place we are living in?’ ”
In the Western world, humans spend 90% of their time
indoors. The average American spends even more than that—93%—inside buildings
or cars. For years scientists have sounded the alarm that our disconnect from the outdoors is linked to a host of chronic
health problems, including allergies, asthma, depression, irritable bowel
syndrome, and obesity. More recently, experts in various fields have begun
studying why buildings, even those designed to be as germ-free as possible, are
vectors for disease, not the least Covid-19.
“There was a study of more than 7,300 cases in China, and
guess how many people caught the disease outdoors?” Leung asks. “Just two.”
Early testing following Black Lives Matter protests in Minnesota also suggested
that transmission of SARS-CoV-2 outside is rare, even when thousands of people
gather, talking, yelling, and chanting—at least when most of those people wear
masks. Out of more than 13,000 protesters tested, only 1.8% were positive.
Other states showed similar results.
Leung says a “misalignment with nature” in building design
is partly to blame for our scourge of chronic diseases and the current
pandemic. The relative lack of air flow
and sunlight is an obvious issue; temperature, humidity, and indoor air
pollution also play a role. But there’s another, less discussed factor: the microbiome of the built environment,
which encompasses trillions of microbes including bacteria, fungi, and
viruses.
Until about 15 years ago, very few scientists—and even fewer
architects, designers, and engineers—paid attention to indoor microbes, with
the exception of problematic outcroppings such as black mold and legionella,
the bacteria that causes Legionnaires’ disease. That changed after the 2001
anthrax attacks, when letters laced with deadly bacteria were mailed to
politicians and the offices of news outlets, killing 5 people and infecting 17
more. Experts at the nonprofit Alfred P.
Sloan Foundation began contemplating what role buildings might play in
mitigating bioterrorism threats. Realizing we knew almost nothing about which
microbes exist indoors, the foundation poured tens of millions of dollars
into research. Soon scientists uncovered rich ecologies of fast-evolving
indoor microbe populations. Crucially, most had little overlap with
outdoor populations, including salutary species that humans co-evolved with
over millions of years.
Now, with a global pandemic raging, these researchers are
suddenly in demand. “Our calendar is fairly full,” says Kevin van den
Wymelenberg, director of the Biology and the Built Environment Center at the
University of Oregon. He used to receive two or three inquiries per week,
asking for advice on how to improve the health of a building. Now he gets 20 a
day. “It’s everyone from hospitals, to large commercial real estate portfolios,
to nursing homes and school districts, to personal friends who run a barber
shop and are trying to decide whether or not they should blow out the hair of
their patrons.”
Of course, the most urgent microbe-related question is where
to find SARS-CoV-2 and how to kill it. Beyond that, there are also long-term
questions. How can we promote indoor
microbe populations that don’t make us chronically ill or harbor deadly
pathogens? Can we actually cultivate beneficial microbes in our
buildings the way a farmer cultivates a field? Experts including Van den
Wymelenberg are confident all this is possible. “I really believe our
building operators of the future and our designers will be thinking about how
to shape the microbiome,” he says.
The term “microbiome” is most often used to refer to the
population of microbes that inhabit our body, many of which help produce
vitamins, hormones, and other chemicals vital to our immune system, metabolism,
mood, and much more. In the typical person, microbial cells are as numerous as
those containing human DNA and cumulatively weigh about 2 pounds. In recent decades our personal microbiomes
have been altered by factors such as poor dietary habits, a rise in cesarean-section
births, overprescription of antibiotics, overuse of disinfectants and other
germ fighters, and dwindling contact with beneficial microbes on animals and in
nature. According a 2015 study, Americans’ microbiomes are about half as diverse as those of the
Yanomami, a remote Amazonian tribe.
Like our bodies, the buildings we inhabit are also teeming
with microbes. “Inhale deeply,” writes Rob Dunn, a professor of applied ecology
at North Carolina State University, in his 2018 book Never Home Alone. “With
each breath you bring oxygen deep into the alveoli of your lungs, along with
hundreds or thousands of species. Sit down. Each place you sit you are
surrounded by a floating, leaping, crawling circus of thousands of species.”
Dunn says more species of bacteria have been found in homes than there are
species of birds and mammals on Earth. In 2015, researchers found that indoor
air contains nearly equal concentrations of bacteria and viruses. (Almost all
viruses are harmless, and some may be beneficial.) Over time these many
microbes have adapted to survive, and even thrive, everywhere from our
pillowcases and toothbrushes to the more extreme climates of our dishwashers,
showerheads, ovens, and freezers.
Many are derived from humans, or likely feed off human
debris. Like Pigpen from the comic strip Peanuts, each of us has a plume of
microbes spewing off our body at a rate of about 37 million bacteria and 8
billion fungal particles per hour; the difference is that our plumes are
invisible to the naked eye. Indoors, the impact is measurable. One study notes
that it takes less than 24 hours for a hotel
guest to colonize a room with their personal microbes, erasing all traces
of previous guests and making the space microbially identical to their home.
Considering our perpetual emanations, it’s easy to envision
how the coronavirus might spread within a room. A single sneeze discharges
roughly 30,000 microbe-filled droplets traveling at up to 200 mph. A cough releases about 3,000
droplets, which reach speeds of 50 mph. A simple exhale produces 50 to
5,000 droplets. We know
that a person infected with influenza releases as many as 33 viral particles
per minute just breathing and about 200 million per sneeze. Meanwhile, exposure
to just a few hundred SARS-CoV-2 particles may be enough to cause infection.
Outdoors our invisible plumes almost always disperse
quickly, which is a very good thing in the case of Covid carriers. “Any virus
that is released into the air is rapidly diluted, moved by wind currents, and
spread out across a seemingly infinite space,” says Linsey Marr, an expert in
infectious disease transmission and professor of civil and environmental
engineering at Virginia Tech. “It’s almost like putting a drop of dye into the
ocean vs. putting it into a glass of water.” Sunlight also inactivates viruses in as little as five
minutes—eight minutes in the case of SARS-CoV-2. A study from the
Department of Homeland Security found that the coronavirus can hang around
indoors in the dark for hours.
Facing an invisible and potentially deadly virus, the
understandable impulse has been to whip out some Clorox and go to battle. But
indiscriminate bleach-bombing could backfire. For one thing, misdirected
efforts may be a colossal waste of time and money. New York City, for example,
announced in the spring that for the first time, it was closing the subway
system during early-morning hours to deep-clean every train. “It’s all
theater!” says Jack Gilbert, a professor and microbiome researcher at the
University of California at San Diego. “You bleach the subway, the bleach dries
up and becomes inactive. If just one person who has Covid-19 interacts with
that surface, the four hours of cleaning have no effect.” And because we now
know SARS-CoV-2 is most often transmitted through the air, cleaning efforts
seem even more futile.
A more serious risk is that attempts to sterilize our surroundings can kill off bacteria critical
for human health—or, even worse, inadvertently promote the survival and
evolution of more dangerous bugs, including antibiotic-resistant superbugs. “We should be worried,” says Rob
Knight, founding director of the Center for Microbiome Innovation and a
professor of pediatrics at UCSD. “If we’re overzealously stripping off all the bacteria that would naturally
be there, then we may be creating homes for bacteria and maybe even viruses
that are harder to remove.”
No amount of chemicals will get rid of everything, and
what’s left behind is often undesirable. Microbiologists have swabbed the
International Space Station to find out what happens inside an enclosed,
supposedly sterile chamber in which every bit of food and equipment has been
disinfected within a
specially designed NASA facility. As it turned out, microbes were everywhere,
almost all of them human derived. Among the most common were bacteria
associated with feces, stinky feet, and armpits, which is perhaps why the ISS has been described as smelling like a
mix of plastics, garbage, and body odor.
Here on Earth, proper hygiene is effective in minimizing
exposure to pathogens such as those that cause food poisoning and strep throat,
but we tend to go nuclear, using harsh chemicals when soap and water could do
the job. For years antimicrobials
have been added to everything—wall paint, kitchen sponges, underwear, lip
gloss. Now we’ve become more extreme.
“It’s just speculation, but we could see a blip where this
generation of kids has more immune-related conditions”
In hopes of zapping SARS-CoV-2 straight out of the air, some
building managers are installing so-called bipolar
ionization units, even though they may not work against Covid and
sometimes generate harmful gases such as the lung irritant ozone. As for
the antimicrobial cleaning agents and
surface coatings being liberally applied throughout offices and other
public spaces, we may be introducing large quantities of poorly understood,
potentially poisonous chemicals into our everyday life—as well as speeding the evolution of
disastrous superbugs.
“The more we use the same antimicrobials in different
contexts, the more opportunity these microbes have to develop resistance,” says
Erica Hartmann, an engineering professor at Northwestern University who focuses
on indoor microbiology and chemistry.
“If they’re developing resistance to the antimicrobial itself, that’s
not great, because then we’ve lost an important product in our cleaning
arsenal. But if they also develop resistance
to clinically relevant antibiotics, of which we have precious few, that’s
an even bigger concern—and there’s evidence that both of those things happen.”
Wiping out good
bacteria along with the bad has also been linked to chronic health
problems. One often-cited series of studies, begun in 1998, examined the relationship between cleanliness and
disease in the Finnish-Russian border region of Karelia, where people share
similar genetics. On the wealthier, cleaner Finnish side, people were as many
as 13 times more likely to suffer from inflammatory disorders as on the
Russian side, where the majority live in rural homes, keep animals, and
cultivate their own gardens.
Our pandemic-era anti-germ crusade may not have a big impact
on the already formed microbiomes of adults. But infants and young children, who need exposure to a wide variety
of microbes to train their developing immune systems, could be more
adversely affected. “It’s just speculation, but we could see a blip where this
generation of kids has more immune-related conditions,” Knight says,
“especially in places where people have had to stay quarantined indoors, where
kids didn’t get to go outside as much.”
Leung of SOM began thinking about the microbiology of
buildings years before the pandemic. It’s not something he tends to mention to
prospective clients. “If you tell a client, ‘Let’s talk about microbes,’
they’ll say, ‘Get out of here—next!’ ” he says. “We have to address it
carefully.”
Beyond using organic
materials and maximizing access to natural light and outdoor spaces, Leung
says lots can be done to make buildings healthier at the microbial level. For
safer air he extols the use of filters designed to eliminate SARS-CoV-2
and other pathogens and contaminants, but he cautions against bipolar
ionization technology and says air
shouldn’t be sterilized over long durations. Whenever possible, Leung
suggests deploying ventilation systems that pump offices full of microbially diverse outdoor air. Among his
current projects is the 31-story WeBank
tower in Shenzhen, which upon completion in 2022 will draw air through
trees planted on balconies before it’s funneled inside. “Sometimes we also open
up buildings at night,” Leung says, noting that the outdoor air is first
measured for pollutants. “During the day people want air conditioning, but
when they’re gone you can recharge the building with microbes from outside.”
Proper ventilation is particularly important in
energy-efficient buildings, which, like spaceships, are designed to be sealed
off from the outside world. In addition to delivering fresh oxygen and
eliminating the brain-numbing buildup of carbon dioxide, good airflow and
filtration reduce exposure to a long list of mostly unregulated and unmonitored chemicals found indoors. These include known
carcinogens and endocrine disrupters, which reside in carpets, computers,
free-floating dust, office chairs, paint, and more. Outdoor pollution also seeps inside buildings and gets trapped,
especially during hours when ventilation systems are turned off. All this means indoor air is often far worse than outdoor
air, with levels of some contaminants rising to 10 times higher or more.
For businesses, better
air quality alone translates to an estimated $6,500 to $7,500 of added
annual productivity per employee, mainly a result of improved wakefulness
and acuity, say Joseph Allen and John Macomber, Harvard professors who in April
published the book Healthy Buildings.
By contrast, they note, a study of more than 3,000 workers in 40 buildings
found that 57% of all sick leave was attributable to bad air.
Disturbingly, Allen and Macomber also write that up to 90% of American schools don’t meet the minimum ventilation requirements—and
that those standards are already far below optimal.
In London, Los
Angeles, Mumbai, and other polluted cities, outdoor air needs to be heavily
filtered before being pumped indoors, and most
beneficial outdoor microbes likely don’t survive. But in cleaner and
greener areas, simply opening windows has proved effective. “After taking antibiotics, you’re supposed to eat yogurt to replenish with probiotics,” says Mark Fretz, a
colleague of Van den Wymelenberg at the University of Oregon, where he’s a
research assistant professor at the Institute for Health in the Built
Environment. “For your buildings, the yogurt is essentially opening your
window.”
In 2012 researchers compared the microbiomes of a hospital
room in Portland, Ore., with operable
windows with one in which windows were permanently sealed. “It was very
difficult to find a hospital that even had an operable window,” Fretz says.
Opening the window, it turned out, resulted in far more microbial diversity
throughout the room, including species found on plants and leaves. Notably,
there was also a significantly lower chance of encountering pathogens. (Side
note: Potted plants also seed indoor
spaces with valuable natural microbes—and they measurably improve human
happiness, physical and mental health, and even original thinking—but they
barely improve air quality.)
Another means of achieving healthier air is humidification, currently an extreme rarity in
North America, as any office worker who’s struggled through a dry and
overheated winter season knows. “Most of our commercial buildings in the U.S. are not humidified,”
Leung says. “And that’s why the pandemic could get even worse this winter.” Not
only does sufficient moisture in the
air allow the human immune system to function at its best, it also causes
viral particles to drop to the floor and die more quickly. According to
some calculations, viruses in dry air can survive six times as long as those in
buildings with a relative humidity of
about 40%.
Of course, building interventions alone can’t eliminate the
risk of SARS-CoV-2 contagion, so it’s best to keep social distancing and
wearing masks. In the meantime, scientists at universities and startups are
racing to develop microbial sensors for air filters, building surfaces,
wastewater, and even indoor air. “We have tools
to help us see the unseen,” Van den Wymelenberg says. For now those
detection tools are in their infancy, relying on the arduous process of
repeatedly collecting samples and transporting them to labs for testing.
“There’s no reason this stuff can’t work. We’re already heavily manipulating the
microbiome in our buildings, just not deliberately”
Gilbert has ambitious plans for microbial interventions in
buildings. Trained as a microbial
ecologist, and with experience working on soils, plants, and marine systems, he was initially skeptical when
he learned the Sloan Foundation was promoting something called the Microbiology
of the Built Environment. “I thought it was a joke,” Gilbert says. “I’ll admit
it, I thought there can’t be much microbiology in the built environment, so why
would anyone be interested?”
Then, in the winter of 2012, he got a visit from Paula
Olsiewski, a program director for the Sloan Foundation. At that point he was a
professor at the University of Chicago, and when the meeting was over, a
blizzard had descended on the city. “I offered to drive her back to her hotel
because I had a car that could handle the snow,” Gilbert recalls. “But it was
snowing so heavily that the drive took two and a half hours, and in that time
she convinced me.”
Now at the forefront of microbiome research, human and
environmental, Gilbert was even permitted to sample President Obama’s
microbiome in 2016. (He’s not allowed to disclose the results.) When the
pandemic hit, Gilbert quickly redirected much of his research funding toward
studying SARS-CoV-2. He has one project together with Knight’s lab to
see how the virus travels through hospitals, where it most often takes up
residence, and whether it piggybacks on nefarious bacteria, as the influenza
virus often does.
He also has a second,
more counterintuitive study under
way: In an undisclosed California hospital, Gilbert is investigating whether adding harmless bacillus bacteria into medical facilities reduces the
prevalence of pathogens, including multidrug-resistant bacteria and
viruses. “If you don’t have anything on a
freshly disinfected surface, and you cough your virus-laden bacteria onto
the table, it will survive there,” Gilbert says. “But if there’s a high enough abundance of bacillus,
then the bacillus will outcompete and exclude other pathogens that land
on the surface.” Similar studies have been done in the past, with encouraging
findings, but Gilbert’s is more rigorous.
The idea of putting bacteria to work cleaning isn’t as
far-fetched as it might sound. In the 1940s a Danish company called Novozymes started selling environmental
microbes for decontaminating wastewater. In the 1980s and ’90s it also
contracted with the U.S. government on a large-scale bioremediation project to
help clean up the Exxon Valdez oil tanker spill. About the same time, Novozymes
sent researchers looking for bugs that might help clean home septic tanks,
restaurant grease traps, pet stains, and much more. Among their best finds were
grease- and odor-cutting bacteria discovered in the outdoor grill
sites of Virginia parks and the kitchen of a Florida restaurant.
Today, Novozymes is worth about $16 billion, and its
microbes are key ingredients in dozens of home-care brands. These include
the likes of Aunt Fannie’s Microcosmic
Probiotic-Powered Multi-Surface Cleanser and Counter Culture Probiotic Cleaning
Tonic. “We clean the way nature has been cleaning for 4 billion
years … with probiotics,” reads Counter Culture’s website. The idea is to
deploy an army of microbes that eat away at dirt, debris, and organic
matter, also degrading the stuff left in cracks and crevices. Last year
even Reckitt Benckiser LLC introduced a
probiotic cleaner called Veo, which the company says will “help
contribute to the balancing of the home microbiome.”
Going a step further, scientists are studying whether
salubrious environmental microbes can be introduced into urban homes to reduce
the prevalence of inflammatory diseases. In Finland, one group seeded the
doormats of city dwellers with about 30 grams (1 ounce) of forest soil so
residents could drag outdoor microbes inside. The six-month experiment showed
the rugs did shift the indoor air to include more outdoor microbes. Next the
researchers want to run a large-scale study to see whether forest-soil-impacted
rugs can improve the immune systems of infants and young children. (Another
Finnish group is bypassing the rugs and simply smearing infants with a soil
preparation to find out if there are health benefits.)
So far no one knows exactly which outdoor microbes are
beneficial or how much exposure is best. Still, a number of startups are
marketing bacteria sprays for homes and businesses. Belgium-based TakeAir advertises an “air enricher” that
disperses soil- and ocean-derived microbes through existing ventilation systems
to create “a 100% natural and protective biosphere for your building
users.” Clients include a Belgian chain of gyms and a housing project in
Antwerp. Another front-runner, Betterair
in Israel, sells “the world’s first organic air and surface probiotic,” a
freestanding microbe mister that retails for $400. (Refill cartridges are
$99.)
It’s only a matter of time before these technologies become
better understood and more widespread. “There’s absolutely fascinating research
to be done,” Gilbert says. “I want to maybe engineer bacillus so it has
properties that can stimulate the immune systems of people in a room.” Van den
Wymelenberg is also hopeful: “There’s no reason this stuff can’t work,” he
says. “We’re already heavily manipulating the microbes in our buildings, just
not deliberately.”
On a Tuesday afternoon in June, Leung takes my call while
teaching his 18-year-old son to drive. Asked about the probiotic air enhancers, he laughs. “It actually says a lot about
human beings,” he says. “We’ve created buildings so sterile that now we have
to buy nature and spray it back in. That’s how silly we are.”
Perhaps the pandemic will serve as a wake-up call. “This is
our chance to right our wrongs of the past 200 years,” he says, speaking of restoring our relationship with soils,
plants, and animals. It won’t be easy. Over the next 40 years, the total
amount of indoor square footage will roughly double worldwide, reports science
journalist Emily Anthes in her book The Great Indoors. Given the horrors of
Covid, many businesses and building managers will also work their hardest to
sanitize indoor environments like never before, perhaps causing unintended
consequences.
In the meantime, the climate crisis is compounding potential
health risks as flooding, wildfires, and man-made disasters destroy the natural
world, exposing us to dangerous new diseases while annihilating the microbes we
likely need to prevent widespread chronic illness (not to mention those we may
need as medicines). Already, Leung says,
urban air is often
depleted of healthful natural bacteria. “In the wintertime, when the
leaves are gone from trees, do you know what the main thing is you find in
urban air?” he asks. “Microbes from animal feces.”
Still, the pandemic may be changing our perspective on
indoor life—and even physically altering our microbiomes. Although some people
are cleaning too much, eating more junk food, and drinking more alcohol, prescriptions for antibiotics are markedly
down from last year, according to the Centers for Disease Control and
Prevention. One explanation is a decrease in non-Covid illnesses as a result
of social distancing.
And though people aren’t mingling as much or sharing
microbes—which can be beneficial when pathogens aren’t involved—those lucky
enough to live where they aren’t required to hole up indoors are spending more
time in nature. “I mean, I see neighbors outside I didn’t even know existed,
and they’re working in dirt that they’re pretending is a garden,” one
microbiome expert says. As businesses allow employees to work from home, many
are also abandoning urban life for greener settings.
But winter is upon us, and the pandemic is surging once
again as more people move indoors. If we don’t adjust our lifestyle and start
making our buildings healthier from a microbial standpoint now, Leung says,
we’ll get hit even harder. “If you think this pandemic is bad, wait another 50
years when we have a much older population and much higher health-care costs.”
In the not-so-distant future, he warns, three interrelated
factors will increasingly affect our well-being: climate change, chronic health
problems, and more pandemics. “We’re going to have to design for that,” Leung
says. “And it’s going to be important to
bring humans and nature together again—like in heaven.”
