UV-C penetrates only the superficial layers of the skin and eye, with the shortest wavelengths hardly penetrating at all to living cells (epidermis), so only a very mild, transitory “sunburn” (erythema) occurs from accidental over-exposure of skin areas. Even though GUV lamps can pose a theoretical delayed hazard, incidental UV exposures in the workplace would not significantly increase one’s lifetime risk for cataract or skin cancer when compared to daily exposure to the UV radiant energy in sunlight. Solar UV is much more penetrating and reaches the germinative (new-cell producing) layers in the skin, with the result that skin cancer risk is significant, and sunburns can be severe. There is a small amount of UV-B (297, 303, 313 nm) from a low-pressure mercury lamp, but this is insignificant unless exposures are experienced at least an order of magnitude or more above the safety limits for 254 nm.
 International Commission on Illumination (CIE). CIE 187:2010, UV-C Photocarcinogenesis Risks from Germicidal Lamps. Vienna: CIE; 2010.