Kobe University-Ushio Inc. Joint Study Finds Repetitive Irradiation with 222 nm UV-C Does Not Cause Skin Cancer

16 Apr 2020

Ushio Inc. 222 nm UV-C Research

Oude Meer, The Netherlands (April 2020) – Ushio Inc. (TYO: 6925; headquarters in Tokyo, Japan) and a research group from Kobe University have demonstrated via animal experimentation that repeated irradiation of 222 nm ultraviolet radiation (UV-C) does not cause skin cancer, suggesting it is safe for human skin and eyes. This technology is expected to be used in a wide range of antibacterial and viral inactivation applications.

The results were published in Photochemistry & Photobiology on March 29, 2020, and will be presented at the 2020 American Society of Photobiology Biennial Meeting in Chicago.

This research was supported by KAKENHI Grants-in-Aid for Scientific Research (JP16k10126).

Highlights

Repeated irradiation of 222 nm UV-C does not cause skin cancer in highly susceptible mice.
Results suggest 222 nm UV-C is also safe for human skin and eyes.
The lamp used included an optical filter for 222 nm wavelength; no skin cancer or cataracts were observed in the mice.
Direct irradiation of 222 nm germicidal lamps on humans is considered safe, enabling broad applications.

Background of Research

Natural UV-C (200–280 nm) is absorbed by the ozone layer. 254 nm UV-C lamps are used for anti-microbial applications but are not safe for human exposure. The 222 nm lamp, developed for medical use, required proof of non-carcinogenic exposure and safety for repeated human exposure.

According to Kobe University, 222 nm UV-C is as effective as 254 nm for disinfection but needed safety confirmation.

Research Methodology

Researchers repeatedly irradiated 222 nm UV-C on xeroderma pigmentosum group A model mice, which are highly susceptible to skin cancer. The lamp included a Kr-Cl excimer lamp and an optical bandpass filter.

All control mice irradiated with UV-B developed skin cancer and eye injuries. No mice in the 222 nm group developed skin cancer or microscopic abnormalities.

222 nm UV-C only penetrates the uppermost skin layer, causing no DNA damage to epidermal cells.

222 nm UV-C irradiation safety diagram — Figure 1: Kobe University-Ushio Inc. study on 222 nm UV-C safety

Future Developments

222 nm UV-C can be directly irradiated on human skin, enabling applications such as hand sanitisation in medical facilities and disinfection in public spaces.

Glossary

Cataracts: Clouding of the eye lens due to protein changes, often from UV exposure.
Xeroderma pigmentosum: A genetic disorder causing high risk of skin cancer from UV exposure.

Research Paper Information

Title: Long-term effects of 222 nm ultraviolet radiation C sterilizing lamps on mice susceptible to ultraviolet radiation
DOI: 10.1111/php.13269
Authors: Nozomi Yamano, Makoto Kunisada, Sachiko Kaidzu, Kazunobu Sugihara, Aiko Nishiaki-Sawada, Hiroyuki Ohashi, Ai Yoshioka, Tatsushi Igarashi, Akihiro Ohira, Masaki Tanito, and Chikako Nishigori
Journal: Photochemistry & Photobiology

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Since 1964, Ushio Group has been a leading manufacturer of specialist industrial light sources. Ushio Europe, established in 1985, offers over 3,000 solutions for various industries. Visit ushio.eu for more information.

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Source: Ushio America Inc.