Naphthalene [BAT Value Documentation, 2018]

Abstract

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”).

Simple and reliable method to simultaneously determine urinary 1- and 2-naphthol using in situ derivatization and gas chromatography-mass spectrometry for biological monitoring of naphthalene exposure in occupational health practice

“…1-NAP and 2-NAP are excreted in the urine as glucuronide and sulfate conjugates. 6 In order to cleave these conjugates, enzymatic hydrolysis was carried out according to the procedure employed in a previous study. 10 IS 1 (5000 µg/L, 20 µL), 0.5 mol/L acetate buffer (pH 5.0, 1 mL), and β-glucuronidase/ arylsulfatase (20 µL) were added to a glass test tube containing urine (2 mL).…”

“…6 Among them, 1-naphthol (1-NAP) and 2-naphthol (2-NAP) have been used as biomarkers for exposure to naphthalene in humans. 6 For non-smokers, the DFG has proposed a biological reference value (Biologischer Arbeitsstoff-Referenzwert, BAR) of 35 μg/L (after hydrolysis) for 1-NAP plus 2-NAP in urine. 6 This BAR defines the urinary 1-NAP and 2-NAP level in the population who are not occupationally exposed to naphthalene (ie, the background level).…”

“…6 For non-smokers, the DFG has proposed a biological reference value (Biologischer Arbeitsstoff-Referenzwert, BAR) of 35 μg/L (after hydrolysis) for 1-NAP plus 2-NAP in urine. 6 This BAR defines the urinary 1-NAP and 2-NAP level in the population who are not occupationally exposed to naphthalene (ie, the background level). No OEL based on biological monitoring for naphthalene has been proposed by the JSOH; also, no biological exposure index for naphthalene has been proposed by the ACGIH.…”

“…OELs have not been proposed by the JSOH or the DFG. More than 30 naphthalene metabolites have been identified in mammals 6 . Among them, 1‐naphthol (1‐NAP) and 2‐naphthol (2‐NAP) have been used as biomarkers for exposure to naphthalene in humans 6 .…”

“…More than 30 naphthalene metabolites have been identified in mammals 6 . Among them, 1‐naphthol (1‐NAP) and 2‐naphthol (2‐NAP) have been used as biomarkers for exposure to naphthalene in humans 6 . For non‐smokers, the DFG has proposed a biological reference value (Biologischer Arbeitsstoff‐Referenzwert, BAR) of 35 μg/L (after hydrolysis) for 1‐NAP plus 2‐NAP in urine 6 .…”