Updated on March 11, 2025 at 4:56pm ET
On the evening of March 7th, 2020, I told a friend that I was on my airport terminal phone and was afraid to write an article that risked ruining my journalistic reputation. I was talking to a small but close aerobologist community about the possibility that the novel coronavirus could easily move from person to person. Scientists emphasized that the idea of airborne transmission of new viruses remains largely theoretical, but they seemed quite concerned.
When my story comes out the following week, as far as I know, it is the first article by a journalist, that the virus causing Covid-19 can travel efficiently through the air, potentially covering many meters of gas clouds released by coughing and sneezing. To avoid excessive worries, I insisted on calling the virus “air.” It said, “Corona Virus is not in the air, but it is definitely tied to the air.” That idea was not immediately accepted. Two weeks later, the World Health Organization tweeted, “Fact: #covid19 is not in the air.” However, as the pandemic unfolds, it has become clear that the coronavirus actually spread through air communication.
By then, parallel ventilation debates have emerged amid loud discussions about mask mandates, vaccine boosters, and individual responsibility for the health of others. Worn an N95 or receiving a third Covid shot was ultimately an individual choice, but breathing safer air in indoor spaces required buy-in from larger players like education departments and transportation. Some supporters maintained clean air as a kind of public interest. If it was successful, this idea would have represented one of the most enduring pathways for governments to reduce the risk of people more commonly from Covid and airborne diseases.
In the United States, the federal government regulates outdoor air quality, but indoor air monitoring is relatively low. The state and local jurisdictions pick up some of the slack, which creates a patchwork of rules regarding indoor air. Local investments in better aviation quality infrastructures also vary greatly. For example, a 2022 survey of Covid ventilation measures in US public school districts found only about a quarter of those expected to use or use HEPA filters with dense meshes that trap indoor air particles. A small percentage (8%) have also installed air rinsing systems incorporating ultraviolet rays that can kill bacteria.
For decades, experts have pushed the idea that governments should pay more attention to indoor air quality. In his new book, Air-Borne: The hidden history of life we breathejournalist Carl Zimmer shows this long arc of debate. He believes Richard Riley, a giant in the aerobic field who helped show that tuberculosis is in the air, believes that there is no need to ensure that the air that individuals breathe is clean. Just as the government regulates the safety of water flowing through indoor pipes, air safety in indoor public spaces must be overseen.
More than half a century ago the coronavirus pandemic, Zimmer reports that Riley positioned the idea as an alternative to broad-based masking requirements, seeking “a kind of benevolent tyranny.” If cleaner air is one of the best ways to reduce the social burden of illness, the two best ways to achieve that were to encourage people to wear masks in public spaces or to install better ventilation. The latter approach means breaking the air – “the individual is freed from direct responsibility.” Riley reasoned in his 1961 book, which he co-authored:
The medical breakthroughs over the next few years may have dented enthusiasm for the idea. Zimmer writes that the world is not particularly interested in the details of airborne disturbance transmission due to the major advances in vaccines in the 1960s. Thanks to the new vaccine, doctors have a way to prevent measles, and WHO has launched a campaign to eradicate natural po, and polio appears to be leaving. In addition, researchers came up with an arsenal of life-saving antibiotics and antivirals. When our defenses were very strong, it wasn’t very important how the virus reached us.
But in the first year or so of the coronavirus pandemic, one of the only defenses against Covid was to avoid it. And when debate escalated over how well the virus spread in the air, the science of aerobicology plunged into the spotlight. Some citizens have begun fighting for good ventilation. Grassroots efforts have emerged to put home-made air purifiers and portable HEPA filters in public places. Teachers opened classroom windows when they learned there was no proper ventilation for the school, travelers began carrying carbon dioxide monitors to measure air quality on planes, and restaurants began offering outdoor meals.
The federal government has taken several small steps to promote better ventilation. In mid-2023, the CDC issued new recommendations that encourage five air changes per hour for every building (essentially replacing all air in a room). But it is a recommendation, not a requirement, but rather that local governments and owners of public buildings are slow to take on the burden of installing or overhauling ventilation systems. Part of that was certainly due to the difficult price tag. In 2020, the government’s Accountability Office estimated that around 36,000 school buildings had substandard systems for heating, ventilation and cooling. The estimated cost of upgrading the system and ensuring safe air quality at all schools in the country is approximately $72 billion for the calculated experts. Portable HEPA filters, on the other hand, are noisy and can require space, making them a less ideal long-term solution.
In most cases, the momentum for improving indoor air quality has faded, as interest waned in the 1960s. Five years after Covid-19 promoted US closures, hospitalization and mortality rates due to illness are only a small part of what was once, and public debates about ventilation have declined. To truly improve indoor air quality on a social scale is a long-term investment (and what the Trump administration seems to be very unlikely to take on, given its reduction in other environmental safety protections). But better ventilation will also limit the costs of non-Covid illnesses. Tuberculosis is in the air, and measles is terribly good at spreading like this. There is also evidence of air seeding of common pathogens such as influenza, which caused an estimated 28,000 deaths in the US during the 2023-24 flu season. The same applies to RSV, or respiratory syncytial virus. This causes 58,000 to 80,000 hospitalizations of children under the age of five in the United States each year, killing as many as 300 children. Virologists are also asking whether avian flu can evolve and efficiently transmit air.
For those of us who are still worried about airborne illness, it feels like it has changed very little. We were at the start of the pandemic. I remember that moment at the airport and later worried about panic. Because during my flight I was the only person wearing an n95, so I was wearing it a few months ago in the dusty crawl space under my house. On the plane, I felt like a weirdo. These days, when I take public transport, I am once again almost always the only masker. Sometimes I feel ridiculous. But just last week, a woman coughed into my head while I was sitting on the subway. At that moment, I was happy to wear a mask. But I would have felt even more at ease if the enclosed space in the metrocar had been designed to cleanse the air of what she might have released and not reach me.
This article originally incorrectly used travelers to measure air quality on planes using carbon monoxide monitors. In fact, they used carbon dioxide monitors.
