Is far-UVC safe for people? What the research shows so far

Why UV safety is a fair question

People have been warned about ultraviolet light for decades, and with good reason. Conventional germicidal UV-C at 254 nm can cause skin burns and painful eye inflammation, and it can damage DNA in living skin cells. So when a device promises UV disinfection while people are in the room, it deserves careful scrutiny.

The physics behind far-UVC safety

The key difference is penetration depth. Light at 222 nm is absorbed so strongly by proteins that it cannot pass through the dead outer layer of the skin, called the stratum corneum, or the tear layer covering the eye. The living cells underneath, which are the ones that matter for burns and skin cancer, are largely shielded. Germicidal 254 nm light, by contrast, penetrates much deeper.

What studies in people show

In a clinical trial at Kobe University in Japan, published in PLOS ONE in 2020, 20 healthy volunteers had areas of their backs exposed to 222 nm light at doses from 50 to 500 mJ/cm². None of them developed skin redness at any dose. At the highest dose, the number of bacteria on the skin fell significantly. The researchers did measure a small but statistically significant increase in a marker of DNA damage in the irradiated skin, which is one reason why experts continue to recommend staying within exposure limits.

A pilot study at the National University Hospital in Singapore treated pressure ulcers in 16 patients with 222 nm light over two weeks. Across 68 sessions, 87% showed a reduction in bacteria, and no adverse events were reported.

Putting it in context with sunlight

A 2021 study from the University of Dundee and NHS Tayside used computer modelling to compare DNA damage in the skin from far-UVC lamps with damage from ordinary sunlight. Under the current exposure limits, the model estimated that it would take around 30,000 hours of a filtered 222 nm lamp to cause the same DNA damage in the deepest layer of the skin as 10 minutes of moderate spring or summer sunshine. The authors also noted that the effects of far-UVC absorbed in the outermost skin layer are not yet fully understood.

Filtering makes a real difference

The same Dundee study found that an unfiltered 222 nm lamp caused far more DNA damage than a filtered one, because unfiltered lamps also emit some longer, more penetrating wavelengths. Animal research from Columbia University reached a similar conclusion: filtered 222 nm light killed MRSA on surgical wounds in mice as effectively as 254 nm light, without the skin damage seen with 254 nm.

What is still being studied

Independent reviews are clear that the evidence is promising but not complete. A 2021 review of over 100 papers noted that long-term, high-dose studies are still limited and that more research on the human eye is needed. The International Ultraviolet Association also points to ozone generation by some lamps as something to measure and manage.

The practical takeaway

For hospitals and clinics, the message from the research is to choose far-UVC systems that use filtered lamps, have been independently tested, and are installed so that exposure stays within recognised limits. Used this way, far-UVC is one of the most promising ways to reduce infections in spaces that are never empty.