Chromosomal alterations in peripheral blood lymphocytes, urinary mutagenicity and excretion of polycyclic aromatic hydrocarbons in six psoriatic patients undergoing coal tar therapy.

Six male non-smoking subjects treated for psoriasis with topical applications of pure coal tar or 4% coal tar-containing ointment were examined in order to assess the genotoxic risk associated with this type of therapy. Mutagenicity in urine samples collected before and during the coal tar therapy was evaluated in the plate incorporation assay on Salmonella typhimurium strain TA98 in the presence of S9 mix and beta-glucuronidase. Total urinary polycyclic aromatic hydrocarbon (PAH) levels were evaluated in parallel by high resolution gas chromatography/mass spectrometry. In addition, sister chromatid exchanges and chromosomal aberrations were also analysed in peripheral blood lymphocytes collected before, during and after the end of the coal tar applications. The results suggest that urinary mutagenicity levels as well as the frequencies of chromosome aberrations and sister chromatid exchanges in lymphocytes are related to the levels of exposure to coal tar. Moreover the kinetics of repair of chromosome damage in relation to different exposure levels and the capacity of the urinary mutagenicity assay to correctly identify the exposure to significant levels of PAH are discussed.