Volume 7 (2026) - Issue 1 (Feb 2026)

Effects of 222-nm Far-UVC Light on Mutagenesis in S. Typhimurium

Tianyi Iris Shen ^1,* , Sephina Cai ² , Jalen Hu ³

¹ Montclair Kimberley Academy, Montclair, New Jersey 07042-1707, United States
² School of Kunming, Kunming, Yunnan Province 650000, China
³ Ramsey High School, Ramsey, NJew Jersey 07446, United States
^*Authors to whom correspondence should be addressed.

Received: 2026-9-13 / Accepted: 2026-10-16 / Published: 2026-10-19

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DOI: https://doi.org/10.37906/isteamc.2026.2

Abstract Far-UVC light (222 nm) has emerged as a promising antimicrobial technology for airborne disinfection due to its limited ability to penetrate the outer dead layers of human skin and eyes. However, its potential to induce permanent mutagenesis—rather than repairable structural DNA damage—remains insufficiently characterized. To evaluate this hazard, we conducted an Ames reverse-mutation assay across three genetically distinct Salmonella enterica serovar Typhimurium strains (TA100, TA102, and TA135), exposing them to 222 nm far-UVC and conventional 254 nm UVC light. After accounting for radiation-induced cell cytotoxicity via initial survival assays (0–80 mJ/cm²), revertant colony counts were measured to identify wavelength-specific mutational mechanisms. Survival assays revealed dose-dependent cell killing, with the repair-deficient strain TA1535 showing the highest sensitivity. Ames assay profiles demonstrated contrasting mutational pathways: conventional 254 nm UVC-induced high reversion in strains TA100 and TA135, confirming direct structural DNA photoproduct formation, whereas 222 nm far-UVC produced a marked surge in TA102 revertants with minimal response in TA100 and TA135. These findings indicate that 222 nm far-UVC is not biologically inert; rather than direct base-pair substitution damage, it drives mutagenesis predominantly through indirect oxidative stress pathways. Safety standards and risk assessments for continuous far-UVC deployment must therefore account for potential cumulative oxidative hazards resulting from repeated daily exposures.

Research Areas: Environment, Health & Medicine, Genetics, Microbes, STEM

Keywords: Mutagenesis, Ultraviolet light, Far-UVC light, Ultraviolet germicidal irradiation, Cytotoxicity, DNA damage, Ames assay