Background: Ultraviolet radiation (UVR) and crude coal tar (CCT) containing PAHs can accelerate the skin-aging process (SAP). However, UVR induces the formation of an important protective factor in SAP (vitamin D).

Objective: To determine the relation of SAP to selected risks and benefits of combined dermal exposure to UVR and coal tar (PAHs).

Methods: The study group consisted of patients with chronic stable plaque psoriasis and treated by Goeckerman therapy (GT; daily dermal application of UVR and 5% CCT ointment). The levels of urinary 1-hydroxypyrene (1-OHP), oxidative stress (DNA and RNA damage), genotoxic damage (chromosomal aberration in peripheral lymphocytes; ABC), 25-hydroxy-vitamin D [25(OH)D] and the PASI score were evaluated before and after GT.

Results: Intensive dermal absorption of PAHs was confirmed by increased levels of 1-OHP (p<0.01). After the therapy, we found an increased level of oxidative stress (p<0.05), an increased level of genotoxic damage (ABC; p<0.001), a high efficiency of the treatment (p<0.001) and an elevated production of 25(OH)D (p<0.01). We also found a relationship between the duration of UVR and the genotoxic damage (p<0.01), vitD (p<0.05) and the PASI score (p<0.05). Furthermore, we found a relationship between oxidative stress and 25(OH)D (p<0.05) and between genotoxic damage and the PASI score (p<0.05).

Conclusion: Dermal exposure to UVR and coal tar (PAHs) enhances the level of oxidative stress and genotoxic damage and thus contributes to SAP. However, the exposure is very effective as a treatment and elevates the production of 25(OH)D, the protective factor in SAP. According to our results, UVR is probably a more hazardous factor in SAP.