A revision of ultraviolet MPEs

The current maximum permissible exposure (MPE) limits for short ultraviolet radiation in ANSI Z136.1 (2014) have not been re-evaluated and updated for decades. With the use of UV-C (100 - 280 nm) excimer lasers in surgical and material processing applications there has been a need to re-study the available biological data for eye and skin exposures in this spectral region. There is no change currently in MPEs as a function of wavelength below 302 nm. In reality, the potential hazards below 270 nm are currently overstated, and dual limits (thermal and photochemical) for pulsed lasers and photochemical limits for lengthy (additive) exposures. At very short wavelengths, such as the 193-nm wavelength of the ArF excimer laser, photons have an absorption depth of less than 1 µm and as a result the photochemical limits can be greatly increased for extended exposures. Proposed updates are provided.