The new war on bad air

In January 1912, in the depths of a New York City winter, an unusual new apartment complex opened on the Upper East Side. The East River Homes were designed to help poor families fend off tuberculosis, a fearsome, airborne disease, by turning dark, airless tenements inside out. Passageways led from the street to capacious internal courtyards, where outdoor staircases wound their way up to each apartment. Floor-to-ceiling windows opened onto balconies where ailing residents could sleep. The rooftops drew tenants outside with covered porches and reclining seats, on which tuberculosis patients convalesced. “It is believed that this type of dwelling will not only be an efficient aid in the actual treatment of cases of incipient tuberculosis, but an even greater benefit will be its influence as a measure of prevention,” wrote Dr. Henry Shively, who ran a tuberculosis clinic and developed the idea for the complex.

One of the paramount lessons of the COVID-19 pandemic is that fresh air matters. Although officials were initially reluctant to acknowledge that the coronavirus was airborne, it soon became clear that the virus spread easily through the air indoors. As the pandemic raged on, experts began urging building operators to crank up their ventilation systems and Americans to keep their windows open. The message: A well-ventilated building could be a bulwark against disease. It was not a novel idea. More than a century ago, when infectious diseases ravaged cities in the United States and Europe, public health reformers preached the power of good ventilation, and open-air homes, hospitals and schools sprang up in New York, London and other locales on both sides of the Atlantic. But over the last century, society lost hold of that idea. Scientific advances turned pathogens into problems that could be solved at the individual, biomedical level, with medicines and vaccines, rather than through infrastructure or societal change. Skylines became crowded with air-conditioned towers. An energy crisis encouraged engineers to seal structures tightly. And by the time the coronavirus arrived, Americans were spending their days in schools, offices and homes that could barely breathe.

“So you get a virus that spread nearly entirely indoors butting up against our building infrastructure that we know is not designed for health,” said Joseph Allen, an expert on healthy buildings at the T.H. Chan School of Public Health at Harvard.

Three years later, many Americans have a new, hard-earned appreciation for the health benefits of clean air. But some experts worry that the lesson may not stick. The COVID-19 public health emergency has now expired, and public attention has shifted to other airborne threats, such as the acrid wildfire smoke that has recently smothered many Eastern cities. Given these developments, it might be tempting to seal our buildings back up again.

That would be a mistake, experts say, especially in an era that is certain to bring more pandemics and air-quality crises. Being better prepared for the future, they say, will require us to avoid the missteps of the past.

“There’s a real history of forgetting, especially in the United States,” said Sara Jensen Carr, an architect at Northeastern University who studies the connection between design and health. “I think we’re on the verge of forgetting the importance of fresh air again.”

In the 19th-century city, infectious diseases — tuberculosis, cholera, smallpox, yellow fever, typhoid — were an ever-present danger. Many aspects of the squalid urban environment, with its overflowing sewers and lack of clean drinking water, fuelled these outbreaks. But poor ventilation was also to blame.

In New York City’s notorious tenements, many rooms lacked windows to the outdoors, and buildings were sometimes packed together so tightly that an open window provided little breeze. Conditions were especially dismal in cellar apartments. “Their foul, damp, sepulchral-like air being never visited by pure air and sunlight, they are fitter receptacles for the dead than the living,” the Association for Improving the Condition of the Poor wrote in an 1853 report. Germ theory had not yet gained widespread acceptance; instead, the longstanding theory of miasma held that disease was the result of “bad air.” So sanitary reformers began calling for an overhaul of urban spaces, including improvements in ventilation. “An abundant supply of fresh air, at a proper temperature, is the first requisite of health in every place,” the Citizens’ Association of New York wrote in a report published in 1865.

New York undertook a variety of reforms, including restricting airless, underground apartments; requiring windows to the outdoors; and providing more space between buildings. Other cities and states developed new building codes and ventilation standards. “Ventilation comes next to godliness,” the president of the American Society of Heating and Ventilating Engineers declared in 1895, at the organization’s annual meeting.

“The entire building is designed around promoting the movement of fresh air,” said Annmarie Adams, an architectural historian at McGill University. Outdoor air became part of the treatment regimen for tuberculosis, inspiring the design of sanitariums and fuelling an open-air school movement that had students attending class on rooftops, in army tents and on ferries.

It is difficult to prove that better-ventilated buildings made a difference. Death rates — both overall and from certain diseases, such as tuberculosis — did drop after New York implemented sweeping sanitary reforms, although these gains cannot be attributed to ventilation alone.

Still, in the decades since, numerous studies have concluded that improving ventilation, including boosting natural ventilation by opening doors and windows, can reduce the transmission risk of numerous infectious diseases, including tuberculosis and influenza. In one recent study, researchers put patients with COVID-19 in a controlled chamber; when they increased the ventilation, the viral load in the air was reduced.

We have an opening to wage a new war on bad air, experts said, one that will be aided by tools and technologies that were not available to 19th-century sanitary reformers. But the key insight, and the animating spirit, is unchanged. “Our buildings,” said Dr. Allen, of Harvard, “should be seen as a public health tool.”