The distribution and excretion of 1-methylnaphthalene in rats exposed to 1-methylnaphthalene by inhalation

Objectives 1-Methylnaphthalene (1-MN) is a constituent of polycyclic aromatic hydrocarbons, the chemicals that have become ubiquitous in the environment as result of natural and industrial process. This paper reports a study on the distribution and excretion of 1-MN in rats after single and repeated inhalation exposure to 1-MN vapor. Material and Methods Male Wistar rats were exposed to 1-MN vapor at nominal concentrations of 50 mg/m³ or 200 mg/m³ in the dynamic inhalation chambers (TSE Systems Head Nose Only Exposure) for 6 h (single exposure) or 5 days (6 h/day, repeated exposure). Blood, urine and tissue samples were collected during and after the exposure. Blood, urine and tissue concentrations of 1-MN were estimated by gas chromatography using the headspace technique. Results The elimination of 1-MN from blood followed an open 2-compartment model. The concentration in rat tissues was dependent on the magnitude and time of exposure. After repeated exposure, the concentration 1-MN in tissue decreased in comparison to single exposure. The elimination of 1-MN with urine after single and repeated exposure to 1-MN occurred mainly in the samples collected during the first day of collection. Conclusions 1-Methylnaphthalene was rapidly eliminated from the blood and tissues of animals exposed by inhalation to 1-MN. In repeated exposure, there was probably a significant increase of 1-MN metabolism in rats exposed to low and high 1-MN doses. Under conditions of repeated 1-MN exposure, no significant systemic 1-MN accumulation could be observed. Int J Occup Med Environ Health 2018;31(6):763–770