Photosensitization: an underestimated risk for workers exposed to natural and artificial optical radiation during work

Introduction
The exposure to optical radiation in the UV and visible range may induce phototoxic and/or photoallergic reactions involving eyes and skin, interacting with photosensitizing chemical agents which may be present in the tissues of these organs. Photosensitizing agents can enter skin and eyes from the tissue surface or from blood (if the chemical is inhaled or ingested), so either local or systemic exposure is possible. A lot of drugs, environmental and occupational pollutants, cosmetic components, plants extracts and food components may exhibit photosensitizing activity. Photosensitization is clearly recognised by the EU directive 2006/25/CE (protection of workers exposed to artificial optical radiation during work).

Methods
Photosensitizing agents, jointly with occupational settings, critical wavelengths, exposure routes, types of reaction and, if available, doses or levels of exposure are reviewed. Also, critical features in health surveillance of workers exposed to photosensitizers are stressed.

Results
A widespread range of chemicals may have photosensitizing properties: a not exhaustive list is reported in some ICNIRP publications devoted to optical radiation. In several indoor and outdoor occupational settings workers may be exposed to optical radiation and photosensitizing chemicals. The authors point out the importance of taking into account photosensitization in the risk assessment procedures and the crucial role of workers’ health surveillance and information in preventing photosensitization reactions.

Discussion
The identification of a photosensitization risk in occupational settings is sometimes difficult. A detailed analysis of the working features is required, but the exposure assessment for a lot of photosensitizers may be hard. Also, occupational exposure limits for both optical radiation and, if existing, photosensitizing chemicals are not necessarily protective with regard to this type of risk. For these reasons health surveillance and information of workers exposed to photosensitizers (including drugs) play a key role in preventing phototoxic and photoallergic reactions.