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

Abstract

Objectives: 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.

Methods: 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.

Results: 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.