Press Releases
November 11, 2022

Long-term Safety of the Eye When Exposed to 222nm UV-C Light Indoors and Its Effect on the Inactivation of Pathogenic Microorganisms

Ushio Inc. and a group of researchers led by Masaki Tanito, professor and Kazunobu Sugihara, assistant professor in the Department of Ophthalmology in Shimane University's Faculty of Medicine observed and researched the safety of 222nm Far UV-C on the eye and also conducted an experiment on its effect on the inactivation of microorganisms. No acute or chronic adverse effects impacting the eyes were found.

The experiment researching microorganism inactivation showed 90% bacterial inactivation of Staphylococcus aureus and 99% bacterial inactivation of φX174 phages. These results were published in Photochemistry and Photobiology on September 8, 2022.

Details of research and experiment

  • Observation and research on the safety of 222nm Far UV-C on the eye

Before and after installation of a unit equipped with Ushio’s Care222 filtered far UV-C disinfection technology, researchers checked for ultraviolet ray-induced eye problems in the healthcare professionals regularly working at a clinic over a one-year period. The results showed no acute or chronic adverse effects.

Figure 1. Ophthalmologic outpatient clinic

Figure 2. Typical case

Table 1. Findings・Microorganism inactivation experimentMicroorganism inactivation tests were conducted at the clinic where the observation and research was performed. The results showed 90% bacterial inactivation of Staphylococcus aureus and 99% inactivation of φX174 phages.

Figure 3. Far UV-C irradiation at 222nm to check the microorganism inactivation effect

Figure 4. Far UV-C irradiation at 222nm to check microorganism inactivation effect (results of Staphylococcus aureus culture)

Figure 5. Far UV-C irradiation at 222nm to check microorganism inactivation effect (results of φX174 phage culture)

The results showed no effect on the eyes or facial skin of humans and showed that microorganisms would be effectively inactivated under the irradiation conditions equivalent to or below the 22mJ/cm2 recommended before 2022 by the ACGIH, the international safety standard for 222nm (threshold limit value, hereinafter “TLV”).1

Ushio collaborated with domestic and international research institutions on the research, and confirmed the safety of 222nm irradiation in regards to acute and chronic disorders in the skin and eyes. In the field of ophthalmology, Ushio will continue to work with Shimane University to conduct more detailed research. We will also continue to contribute to the establishment of a secure and safe society using light, in the pursuit of antiviral measures at medical institutions, social welfare facilities, aircraft, passenger ships, and other spaces; and the commercialization of filtered far UV-C technology with a focus on its application in medical devices.

1 ACGIH (American Conference of Governmental Industrial Hygienists) recommends the threshold limit value (TLV) regarding acute disorder from ultraviolet radiation. Based on the ACGIH's TLV recommendation, international standards established in different regions (IEC, UL, JIS) specify acceptable amounts of ultraviolet rays, including 222nm.


About the paper published in Photochemistry and Photobiology
  • Information about the paper
    Title: “One-year ocular safety observation of workers and estimations of microorganism inactivation efficacy in the room irradiated with 222-nm far ultraviolet-C lamps.”
    Authors: Kazunobu Sugihara, Sachiko Kaidzu, Masahiro Sasaki, Sho Ichioka, Yuji Takayanagi, Hiroshi Shimizu, Ichiya Sano, Katsunori Hara and Masaki Tanito
    Journal: Photochemistry and Photobiology. 2022, currently being printed

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