Skip to Content
MIT News: 77 Mass Ave

Germicidal danger

While useful for killing pathogens like those that cause covid-19 and the flu, sanitizing ultraviolet lights may cause unwanted chemical reactions that create indoor air pollution.

a UV lamp in a room with framed pictures of virus shapes
José-Luis Olivares/MIT | iStock

Devices that emit germicidal ultraviolet light at a wavelength considered safe for humans have been touted as a way to reduce airborne pathogens like SARS-Cov-2 in poorly ventilated indoor spaces, but new lab experiments show they can produce compounds that are dangerous to breathe.

The trouble begins when the ultraviolet light interacts with oxygen to form ozone, which is itself a health risk. “But also, once you make ozone, there’s a possibility for all these other oxidation reactions,” says Jesse Kroll, professor of civil and environmental engineering, who reported the results with colleagues at MIT and elsewhere. 

“If you have volatile organic compounds in the environment, which you do basically in all indoor environments, then these oxidants react with them and you make these fine particles and oxidized volatile organic compounds, which in some cases turn out to be more harmful to human health than their unoxidized precursors,” adds Victoria Barber, who worked on the research as an MIT postdoc and is now an assistant professor at UCLA. 

While the researchers still see a potentially significant role for the germ-killing lights, they say it’s important to use them with appropriate ventilation and not as a substitute for it. 

Keep Reading

Most Popular

10 Breakthrough Technologies 2024

Every year, we look for promising technologies poised to have a real impact on the world. Here are the advances that we think matter most right now.

Google DeepMind used a large language model to solve an unsolved math problem

They had to throw away most of what it produced but there was gold among the garbage.

The worst technology failures of 2023

The Titan submersible, lab-grown chicken, and GM’s wayward Cruise robotaxis made our annual list of the worst in tech.

AI for everything: 10 Breakthrough Technologies 2024

Generative AI tools like ChatGPT reached mass adoption in record time, and reset the course of an entire industry.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at with a list of newsletters you’d like to receive.