Many efforts to reduce transmission of diseases like Covid-19 and the flu have focused on measures such as masking and isolation, but another useful approach is reducing the load of airborne pathogens through filtration or germicidal ultraviolet light. Conventional UV sources can be harmful to eyes and skin, but newer sources that emit at a different wavelength, 222 nanometers, are considered safe.

However, new research from MIT shows that these UV lights can produce potentially harmful compounds in indoor spaces. While the researchers emphasize that this doesn’t mean the new UV lights should be avoided entirely, they do say the research suggests it is important that the lights have the right strength for a given indoor situation, and that they are used along with appropriate ventilation.

The findings are reported in the journal Environmental Science and Technology, in a paper by recent MIT postdoc Victoria Barber, doctoral student Matthew Goss, Professor Jesse Kroll, and six others at MIT, Aerodyne Research, and Harvard University.