The global health authorities are gradually accepting something that many researchers have argued for over a year: the coronavirus can spread through the air.
That new acceptance, by the World Health Organization (WHO) and the US Centers for Disease Control and Prevention (CDC), comes with strong implications as scientists are calling for ventilation systems to be completely restructured like public water supplies were in the 1800s after pipes were found to harbor cholera.
Cleaner indoor air won’t just fight the pandemic, it will minimize the risk of catching flu and other respiratory infections that cost the world more than $50 billion a year, researchers said in a study in the journal Science. Avoiding these germs and their associated sickness and productivity losses would, therefore, balance the cost of upgrading ventilation and filtration in buildings.
“We are used to the fact that we have clean water coming from our taps,” said Lidia Morawska, a distinguished professor in the school of earth and atmospheric sciences at the Queensland University of Technology in Brisbane, Australia, who led the study. Likewise, “we should expect clean, pollutant- and pathogen-free air” from indoor spaces, she said.
The study’s authors, comprising 39 scientists from 14 countries, are demanding universal recognition that infections can be prevented by improving indoor ventilation systems. They want the WHO to extend its indoor air quality guidelines to cover airborne pathogens, and for building ventilation standards to include higher airflow, filtration and disinfection rates, and monitors that enable the public to gauge the quality of the air they’re breathing.
Relevance in the COVID-19 era
SARS-CoV-2 (COVID-19 causing virus) multiplies in the respiratory tract, enabling it to spread in particles of varying sizes emitted from an infected person’s nose and throat during breathing, speaking, singing, coughing and sneezing.
The biggest particles, including visible spatters of spittle, fall fast, settling on the ground or nearby surfaces, whereas the tiniest aerosols invisible to the naked eye can be carried farther and stay aloft longer, depending on humidity, temperature and airflow. It’s these aerosol particles, which can linger for hours and travel indoors, that have started the controversy.
Although airborne infections, like tuberculosis, measles and chickenpox are harder to trace than pathogens transmitted in tainted food and water, research over the past 16 months supports the role aerosols play in spreading the pandemic virus.
That’s led to official recommendations for public mask-wearing and other infection-control strategies. But, even those came after aerosol scientists lobbied for more-stringent measures to minimize risk.
Ms. Morawska and a colleague published an open letter backed by 239 scientists last July requesting authorities endorse additional precautions, such as increasing ventilation and avoiding recirculating potentially virus-laden air in buildings.
Is 1-meter enough?
WHO guidance has been amended at least twice since, though the Geneva-based organization maintains that the coronavirus spreads “mainly between people who are in close contact with each other, typically within 1 meter,” or about 3 feet.
But Ms. Morawska, who heads a WHO collaborating center on air quality and health, says that’s an oversimplification. “There’s nothing magic about this 1 meter,” she said. The closer to an infected person, the higher the concentration of infectious particles and the shorter the exposure time needed for infection to occur. “As you are moving away, the concentration decreases.”
Ms. Morawska said she hopes the attention that the pandemic has drawn to face masks and the risks associated with inhaling someone else’s exhaled breath will be a catalyst for cleaner indoor air. “If we don’t do the things we are saying now, next time a pandemic comes, especially one caused by a respiratory pathogen, it will be the same,” she said.