Ocular UV protection : revisiting safe limits for sunglasses standards.

Abstract

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) establishes that the safe limits regarding ultraviolet radiation exposure in the spectral region 180nm–400nm incident upon the unprotected eye(s) should not exceed 30 Jm-2 effective spectrally weighted (spectral weighting factors are provided by ICNIRP); and the total (unweighted) ultraviolet radiant exposure in the spectral region 315nm–400nm should not exceed 104 Jm-2. However, it should be considered that the spectral range from 180nm–280nm does not reach the surface of the Earth, since it is absorbed by the ozone layer of the atmosphere. The Brazilian Standard for sunglasses protection, NBR15111(2004), as well as the British Standard BSEN1836(2005) and American Standard ANZI Z80.3(2009), requires the UV protection in the spectral range 280nm–380nm, but does not take into account the total (unweighted) UVA radiant exposure. These limits are discussed in this work and calculations have been made for 27 state capitals of Brazil to understand the limits that should be involved in order to protect the eyes of the Brazilian population. These calculations and considerations may be extended to other countries as well. As a conclusion, we show that the upper limit for the UVA protection of 400nm should be included in the Brazilian standard, as well as the irradiance limits. Furthermore, the parameters for the resistance to irradiance test required on the Brazilian standard are also discussed herein as well the significance of this test. We show that the test should be performed by the sun simulator for a longer period than currently required.