The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated a BAR (“Biologischer Arbeitsstoff Referenzwert”) for naphthalene, considering 1‐ and 2‐naphthol in urine to characterize the internal exposure. Naphthalene is classified in category 2 for carcinogenic substances and designated with an “H” because of its contribution to the toxicological hazards due to penetration through the skin in vitro and dermal absorption in vivo.
In a number of biomonitoring studies, the excretion of 1‐ and 2‐naphthol in urine of persons occupationally not exposed to naphthalene was examined. Tobacco smoking affects the naphthol excretion significantly, thus non‐smokers and smokers have to be considered separately. Up to now, no data of representative collectives of the German general population are available. Therefore, the largest German study was considered for the evaluation, where urine samples of 95 non‐smokers were analysed and a 95th percentile for the sum of 1‐ and 2‐naphthol (after hydrolysis) of 33.6 µg/l (30.6 µg/g creatinine) was found. These results are in good accordance with other national and international studies. Therefore, a BAR of 35 µg 1‐ plus 2‐naphthol (after hydrolysis)/l urine was evaluated for non‐smokers. Sampling time is at the end of exposure or the end of the working shift and after long term exposure at the end of the working shift after several shifts. For the interpretation of the result, the smoking status of the persons has to be considered. In case of an occupational co‐exposure to other polycyclic aromatic hydrocarbons (PAH), the analysis of additional PAH‐metabolites is recommended (see MAK Documentation “Polycyclic Aromatic Hydrocarbons”).