- Scientists are calling for ventilation systems to be overhauled in the same way as public water sources were in the 1800s after cholera was detected in foetid pipes.
- The authors demand the universal acknowledgement that improving indoor ventilation will help prevent infections.
- The researchers stated, “To reduce the risk of infection, avoid spending prolonged periods of time in densely populated areas.”
A subtle revolution has swept the world of medicine. Authorities have finally admitted what many scientists have been saying for over a year: the coronavirus could spread through the air.
The World Health Organization and the U.S. Centers for Disease Control and Prevention’s new acceptance has concrete implications: Scientists are calling for ventilation systems to be overhauled in the same way as public water supplies were in the 1800s after cholera was discovered in foetid pipes.
Researchers said in a report published in the journal Science on Friday that cleaner indoor air will not only combat the pandemic, but will also reduce the risk of catching flu and other respiratory infections, which cost the United States more than $50 billion last year. The cost of improving ventilation and filtration in buildings will be offset by avoiding these germs and their related illness and productivity losses.
“We are accustomed to having clean water flowing from our taps,” said Lidia Morawska, a distinguished professor in the Queensland University of Technology’s School of Earth and Atmospheric Sciences in Brisbane, Australia, who led the research. Similarly, she said over Zoom, “we should expect safe, pollutant- and pathogen-free air” from indoor spaces.
The study’s authors, a group of 39 scientists from 14 countries, are calling for universal acceptance that better indoor ventilation systems will help prevent infections. They want the WHO to expand its indoor air quality guidelines to include airborne pathogens, as well as higher airflow, filtration, and disinfection rates, as well as sensors that enable the public to assess the quality of the air they’re breathing.
They wrote that a “paradigm change on the scale that occurred in 1842 when Chadwick’s Sanitary Report led the British government to encourage cities to integrate clean water sources and centralised sewage systems.”
“No one takes responsibility for the air,” said Morawska. “It’s sort of assumed that the air could be of any quality — that it could contain viruses and pathogens.”
SARS-CoV-2 multiplies in the respiratory tract, allowing it to spread in small particles released by an infected person’s nose and throat during breathing, humming, coughing, and sneezing.
The biggest particles, such as visible spittle spatters, fall quickly and settle on the ground or surrounding surfaces, while the tiniest particles, such as invisible aerosols, can be carried further and remain aloft for longer, depending on humidity, temperature, and airflow.
The debate has been sparked by these aerosol particles, which can persist for hours and migrate indoors.
While airborne infections such as tuberculosis, measles, and chickenpox are more difficult to track than pathogens spread through contaminated food and water, research conducted over the last 16 months supports the involvement of aerosols in the pandemic virus’s spread.
Official guidelines for public mask use and other infection-control measures have resulted as a result of this. Those, too, came after aerosol scientists lobbied for stricter controls to reduce risk.
Last July, Morawska and a colleague released an open letter supported by 239 scientists urging authorities to support additional precautions including increased ventilation and avoiding recirculating potentially virus-laden air in buildings.
Though the Geneva-based organisation maintains that the coronavirus spreads “mainly between people who are in close contact with each other, usually within 1 metre,” or around 3 feet, WHO advice has been updated at least twice since then.
That is an oversimplification, according to Morawska, who is the director of a WHO collaborating centre on air quality and health.
“This 1 metre isn’t magical,” Morawska said. The higher the concentration of infectious particles and the shorter the time it takes for infection to occur, the closer you are to an infected individual. “The focus drops when you move away,” she said.
According to Morawska, in poorly ventilated, enclosed indoor spaces, infectious aerosols remain concentrated in the air for longer.
While a high density of people in such settings raises the number of people who may be exposed to an airborne infection, enclosed indoor spaces that aren’t crowded can also be dangerous, according to Morawska.
“The WHO is gradually modifying the language,” she explained.
According to Raina MacIntyre, professor of global biosecurity at the University of New South Wales in Sydney, Morawska, a Polish-born physicist who was previously a fellow of the International Atomic Energy Agency, can take credit for the WHO’s shifting stance.
“Professor Morawska’s contribution had a real impact by pushing WHO’s hand,” MacIntyre said in an email, citing her “world-leading experience in aerosol research.”
Last week, MacIntyre wrote in The Conversation that the position of airborne transmission “has been denied for too long, partly because expert groups that advise government have not included engineers, aerosol scientists, occupational hygienists, and multidisciplinary environmental health experts.”
“For over a year, a false narrative dominated public discourse,” she said. “While the pandemic wreaked mass devastation on the planet, this culminated in hygiene theatre — scrubbing of hands and surfaces for little benefit.”
Since “they don’t want to lose face,” Julian Tang, a clinical virologist and honorary associate professor in the department of respiratory sciences at England’s University of Leicester, said some people employed in infection prevention and control and related fields have stuck rigidly to beliefs that minimised aerosol transmission despite evidence to the contrary.
“As new data becomes accessible, we all have to adapt and progress,” Tang said. This is particularly true in public health, where “outdated and unsupported thinking and behaviours can cost lives,” he said.
Morawska expressed her hope that the pandemic’s emphasis on face masks and the dangers of inhaling someone else’s exhaled breath would spur the adoption of healthier indoor air.
“If we don’t do what we’re saying now, the next time a pandemic, particularly one triggered by a respiratory pathogen, comes along, it’ll be the same,” she said.