1,2-Dihydroxynaphthalene as biomarker for a naphthalene exposure in humans.

The possibly carcinogenic properties of naphthalene are, regarding to its ubiquitary presence, of environmental-medical and occupational-medical importance. Seven isomeric dihydroxynaphthalenes (DHN) were examined for their suitability as biomarkers in human biomonitoring and to get insights in human naphthalene metabolism. We developed a GC-MS-method for the quantification of 1,2-, 1,4-, 1,5-, 1,6-, 1,7-, 2,6- and 2,7-DHN after solid phase extraction and derivatization with BSA/TMCS. The internal burden of DHN after exposure to naphthalene was determined by measuring urine collected from smokers and non-smokers among the general population and among occupationally exposed persons. The elaborated method can be regarded as specific and sensitive procedure to quantify the seven different DHN. In human urine, we detected 1,2-DHN as main metabolite in 54 of the 55 analysed samples. Median 1,2-DHN values (range) were 1012 μg/L (22-6477 μg/L) for workers and 8 μg/L (<LOD-62 μg/L) for controls. 1,4-, 1,7-, 2,6- and 2,7-DHN were quantified in 61-89% of the samples (range <LOD-113 μg/L). 1,5- and 1,6-DHN were not detected in human urine. In the urine samples of workers, median-concentrations of 1,2-DHN were about tenfold higher than those of the established biomarkers 1- and 2-naphthol, while in our control collective comparable concentration of 1,2-DHN and 1- and 2-naphthol were found. 1,2-DHN showed to be the most sensitive biomarker for an internal exposure to naphthalene. It is clearly superior to 1- and 2-naphthol which up till now have been used for biomonitoring purposes. Moreover 1,2-DHN is the precursor of the possibly ultimate carcinogenic metabolite of naphthalene, 1,2-naphthoquinone. This way the diagnostical reliability of 1,2-DHN predominates the other naphthalene metabolites. So out of analytical and diagnostical reasons 1,2-DHN seems to be the most promising biomarker for the estimation of environmentally and occupationally caused internal exposures to naphthalene.