Humans in the 21st century spend most of their time indoors, but the air we
breathe inside buildings is not regulated to the same degree as the food we
eat and the water we drink. A group of 39 researchers from 14 countries,
including two from the University of Colorado Boulder, say that needs to
change to reduce disease transmission and prevent the next pandemic.
In a Perspectives piece published in Science May 14, they call for a
"paradigm shift" in combating airborne pathogens such as SARS-CoV-2, the
virus that causes COVID-19, demanding universal recognition that respiratory
infections can be prevented by improving indoor ventilation systems.
"Air can contain viruses just as water and surfaces do," said co-author
Shelly Miller, professor of mechanical and environmental engineering. "We
need to understand that it's a problem and that we need to have, in our
toolkit, approaches to mitigating risk and reducing the possible exposures
that could happen from build-up of viruses in indoor air."
The paper comes less than two weeks after the World Health Organization
(WHO) changed its website to acknowledge that SARS-CoV-2 is spread
predominantly through the air, and 10 months after the WHO acknowledged the
potential for aerosol transmission and 239 scientists (including Miller and
Jose-Luis Jimenez) signed an open letter to medical communities and
governing bodies about the potential risk of airborne transmission. The
researchers now call on the WHO and other governing bodies in this new
article to extend its indoor air quality guidelines to include airborne
pathogens and to recognize the need to control hazards of airborne
transmission of respiratory infections.
Such a shift in ventilation standards should be similar in scale to the 19th
century transformation that took place when cities started organizing clean
water supplies and centralized sewage systems. But it would also correct a
major scientific misperception that arose around the same time.
When people in London were dying of cholera in the 1850s, scientists assumed
the disease was airborne. But British physician John Snow discovered that
microorganisms in contaminated water were the reason. Similarly, Hungarian
physician Ignaz Semmelweis showed that handwashing before delivering a baby
greatly reduced postpartum infections. While these discoveries encountered
great resistance in their time, scientists eventually agreed that in these
cases, water and hands--not air--were the vector for disease.
Then in the early 20th century, American public health expert Charles Chapin
erroneously attributed respiratory infections caught in close proximity to
other people to large droplets produced by an infected person, which fall
quickly to the ground. As a result, he stated that airborne transmission was
almost impossible.
Yet in 1945, scientist William Wells published a paper in the predecessor to
Science, lamenting that while we were investing in disinfecting water and
keeping our food clean, we had done nothing for our indoor air, given the
denial of airborne transmission. His research on measles and
tuberculosis--caused by airborne pathogens--challenged this notion in the
20th century, but didn't break it.
Now that the research on SARS-CoV-2 finally has brought to light that many
respiratory diseases can be transmitted through the air, researchers argue
that we must take action.
"Let's now not waste time until the next pandemic," said said co-author
Jose-Luis Jimenez, fellow in the Cooperative Institute of Research Sciences
(CIRES) and professor of chemistry at CU Boulder. "We need a societal
effort. When we design a building, we shouldn't just put in the minimum
amount of ventilation that's possible, but instead we should keep ongoing
respiratory diseases, such as the flu, and future pandemics in mind."
The long-standing misunderstanding of the importance of airborne
transmission of pathogens has left a large gap of information in how to best
construct and manage building ventilation systems to mitigate the spread of
disease--with the exception of some manufacturing, research and medical
facilities. Instead, buildings have focused on temperature, odor control,
energy use and perceived air quality. So while there are safety guidelines
for chemicals such as carbon monoxide, there are currently no guidelines,
globally or in the U.S., that regulate or provide standards for mitigating
bacteria or viruses in indoor air resulting from human activities.
"Air in buildings is shared air--it's not a private good, it's a public
good. And we need to start treating it like that," said Miller.
Lidia Morawska, lead author on the article and director of Queensland
University of Technology's International Laboratory for Air Quality and
Health, said there needs to be a shift away from the perception that we
cannot afford the cost of control. She notes that the global monthly cost
from COVID-19 had been conservatively estimated as $1 trillion and the cost
of influenza in the U.S. alone exceeded $11.2 billion annually.
While detailed economic analysis has yet to be done, estimates suggest
necessary investments in building systems may be less than 1% of the
construction cost of a typical building.
Ventilation systems should also be demand-controlled to adjust for different
room occupancies, and differing activities and breathing rates, such as
exercising in a gym versus sitting in a movie theatre, according to
Morawska. For spaces that cannot improve ventilation to an appropriate level
for the use of the space, she said air filtration and disinfection will be
needed.
Because buildings consume over one-third of energy globally, much from
heating or cooling outdoor air as it is brought indoors, it would be useful
to design a "pandemic mode," that would allow for buildings to only use more
energy when necessary, said Jimenez.
The researchers also call for national comprehensive indoor air quality
(IAQ) standards to be developed and enforced by all countries, and for this
information to be available to the public.
For this to happen, however, many more than scientists will need to
understand its importance.
"I think there is a certain amount of demand that needs to start coming from
the consumer and from the person who works in these indoor spaces in order
to push change," said Miller.
Reference:
Morawska L, Allen J, Bahnfleth W, et al. A paradigm shift to combat indoor
respiratory infection. Science. 2021;372(6543):689-691. doi:
10.1126/science.abg2025