Ed Nardell

In the late 1970s, Edward Nardell, MD, of the Division of Global Health Equity and Pulmonary Division, decided to become an expert on tuberculosis (TB). Friends and colleagues raised their eyebrows: “People said, ‘Why are you doing that?’” Nardell recalled. “They said, ‘TB used to be a problem, but it’s no longer a problem.’”

In fact, TB remains the leading cause of death from a single infectious agent, resulting in the deaths of 1.4 million people worldwide in 2019. “Year in and year out, tuberculosis kills people on the order of the COVID-19 pandemic,” Nardell said. “I suspect that deaths due to COVID-19 will exceed those due to tuberculosis this year, but TB isn’t going away.”

The relentlessness of TB has driven researchers like Nardell to spend their careers studying the transmission and prevention of respiratory diseases—work that has received renewed interest during the COVID-19 pandemic. As restaurants, office buildings, transportation hubs, and community facilities reimagine operations, they are seeking assistance from experts like Nardell, who has conducted pioneering work in air disinfection.

Lessons from Outbreaks Past

It was 1977, and Nardell, fresh out of his pulmonary medical training at Massachusetts General Hospital, began working for the Boston Department of Public Health.

“I was assigned to do TB-control when it was considered to be, frankly, relatively unimportant,” he said.

But two notable events soon transpired. One, with a less immediately evident impact on Nardell’s career, occurred in 1983, during a TB outbreak among Haitian immigrants in Cambridge. Nardell offered an outreach-worker position to a young medical student at Harvard named Paul Farmer. Years later, Farmer, MD, MPH, would become a prominent physician, anthropologist, and Nardell’s own division chief at the Brigham.

The second incident presented more direct implications for Nardell’s work. In 1985, the U.S. experienced a resurgence of TB, and Nardell, at that point the TB control officer for the Massachusetts Department of Public Health, led the response to an outbreak at the Pine Street Inn homeless shelter in Boston. TB experts largely assumed transmission between individuals at the shelter was unlikely because many guests had previously been exposed to TB, and reinfection was thought to be impossible. Nardell, however, discovered that reinfection was occurring at the shelter, and his findings were published in the New England Journal of Medicine.

In pondering how to stop TB transmission at a communal center like a shelter, Nardell remembered a lecture by famed pulmonologist and TB expert Richard Riley, MD, describing ultraviolet (UV) germicidal irradiation, a method of killing airborne bacteria and viruses. Unlike UV light from the sun, which penetrates the skin and can cause cataracts or cancer, properly installed UV germicidal irradiation has no long-term or severe side effects, though it can cause mild skin or eye irritation. The UV light is applied above individuals’ heads, in the “upper room,” and disinfection occurs as air from the upper room mixes with the air breathed in the “lower room” by its inhabitants.

Nardell contacted Riley, and together they installed UV air disinfection in the homeless shelter. Since then, he’s worked in other shelters, hospitals, clinics, and correctional facilities to install germicidal UV. Cambridge Hospital, where Nardell worked for many years, uses the technology, as does the Brigham.

This form of air purification is quite effective, but Nardell believes it is under-utilized, especially in high-income countries with advanced heating, ventilation, and air conditioning systems. Nardell spent a large part of his career working in countries where TB burdens are high and where the only practical way to maintain adequate levels of air disinfection is through upper room germicidal irradiation. Elsewhere, air purification systems tend to use the principles of ventilation (bringing fresh air into the room) and filtration (catching particles in the air using filters), but these tactics are less effective in combatting airborne pathogens.

“Lighting experts may know about UV irradiation, but they’re not involved in public health issues,” Nardell said. “This technology is not taught to engineers, so it really has fallen between disciplines, and a lot of people don’t know about it.”

With the COVID-19 pandemic, however, this has begun to change.

A New Niche

In the wake of the Pine Street Inn outbreak and the 1985 to 1992 resurgence of TB in the U.S., Nardell spent decades continuing to study air disinfection. A large part of his research has been centered in South Africa, where he works in a unique air sampling facility containing hundreds of guinea pigs — one of three of its kind ever built — to study TB transmission and intervention.

Much of his research has focused on controlling TB in limited-resource settings, which are well-suited for UV irradiation. “The routine germicidal UV that we’ve been using for decades is actually fairly inexpensive,” Nardell said, noting that a fixture costs between $500 and $700 if made in-country. “If you compare upper room germicidal UV and air changes per hour with mechanical ventilation, upper room is much cheaper.”

Amidst the COVID-19 pandemic, Nardell believes that UV technologies can offer promising public health solutions. The Division of Global Health is working with Oklahoma homeless shelters to install UV germicidal irradiation, and Nardell hopes that similar projects will be undertaken in other resource-limited settings, such as correctional facilities and public schools, where ventilation systems may be poor.

Thus far, many of the groups installing UV technologies are well-resourced. They include airports, a Cambridge private school, and a flagship London coffee shop, which is using more expensive forms of germicidal UV that are less penetrating and can therefore be used in confined spaces. The airline industry is exploring the possibility of using this form of germicidal UV, called “Far UV,” on airplanes, and the Seattle Space Needle uses it in its elevator.

“It’s not widely available yet, but in the next few months you’ll see more of it,” Nardell said. “It will hopefully become cheaper over time as it becomes more common.”

By using these technologies, restaurants, transit centers, retail spaces, and salons may be better equipped to create environments that limit COVID-19 transmission. Nardell emphasizes that unlike TB, COVID-19 appears to be transmitted in a variety of ways, making air disinfection just one tool in the COVID-19-response arsenal, but a promising one nonetheless.

“For many years, we’ve been trying to train people in these technologies,” Nardell said. He has co-directed a summer course at the Harvard T.H. Chan School of Public Health called “Building Design and Engineering Approaches to Airborne Infection Control,” which brings together architects, engineers, and health care workers from around the world to address public health challenges.

“My own father was a builder and I always felt interested in buildings,” Nardell said. “To be involved in the space between the build environment — architecture and engineering — and medicine has been very rewarding.”

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