(Mono-) Exposure to Naphthalene in the Abrasives Industry: Air Monitoring and Biological Monitoring

Abstract

Exposure to the bicyclic aromatic hydrocarbon naphthalene occurs in most cases along with other polycyclic aromatic hydrocarbons. Here we report from an investigation of 63 healthy, non-smoking male employees in the abrasives industry where naphthalene is the only relevant chemical exposure. Exposure assessment was performed using a combination of Air and Biological Monitoring over nearly a whole working week (Mo.–Th.). Air measurements were carried out during the shift on Thursday with the GGP mini-sampling system, combining particle and vapour sampling at low flow rates. In urine spot samples, the metabolites 1- and 2-naphthol were measured Mo.–Th. pre- and post-shift (for the reference group only Mo. pre- and Th. post-shift). With regard to naphthalene concentrations measured in air and concentrations of its metabolites (1- and 2-naphthol) in urine, study participants could be divided into a high and a low exposure group, and a reference group. The naphthalene concentration in air was in the range of 0.1–11.6 mg m−3, and naphthol concentrations (sum of 1- and 2-naphthol) in post-shift urine were in the range of <1 to 10 127 µg l−1. Naphthalene concentrations in air and naphthol concentrations in urine were closely correlated, indicating mainly airborne exposure at the investigated workplaces. As expected from toxicokinetic data, internal body burden increased slightly during a working week and did not completely decline over a work-free weekend to background concentrations observed in occupationally not exposed persons. Taking into account the observed increase in pre- and post-shift values during the working week, urine sampling for Biological Monitoring at workplaces should be carried out after several preceding shifts. Our data allow the derivation of biological limit values for the sum of 1- and 2-naphthol in urine corresponding to occupational exposure limits for naphthalene in air.

Naphthalene: irritative and inflammatory effects on the airways

“…The goal was to evaluate the irritative and inflammatory effects of naphthalene on the eyes and the airways in exposed workers by using a series of various enpoint measures including self-reported work-related complaints and intensities of odor and irritation perception, nasal endoscopy, smell sensitivity, and inflammatory markers in serum, NALF and IS. A previous report on this cohort revealed that naphthalene in air was high and, specifically in working areas with direct handling of naphthalene, short-term peak concentrations up to 145.8 mg/m 3 could be observed (Weiss et al 2020 ).…”

“…These assumptions have been confirmed specifically for our collective. In example, previously published data on exposure to naphthalene in the collective presented here (Weiss et al 2020) revealed high naphthalene shift concentrations up to 11.6 mg/m 3 with short-term peak concentrations up to 145.8 mg/m 3 (e.g., sieving pure naphthalene). In addition, biological monitoring revealed 1-and 2-naphthol concentrations in post shift urine up to 10.1 mg/L.…”

“…Exposure assessment (air and biological monitoring) in all groups has been previosly outlined in detail (Weiss et al 2020 ). In brief, median naphthalene concentrations in air (Thursday) in the highly and moderately exposed group was 6.30 mg/m 3 and 0.59 mg/m 3 , whereas it was 0.13 mg/m 3 in the controls and thus well below the former occupational exposure limit of 0.5 mg/m 3 in Germany (AGS 2011 ) (Table 2 ).…”

“…Based on previously published data on exposure assessment in air, results on biological monitoring, and workplace description and working history, the participants could be divided into a highly ( n = 22) and a moderately exposed ( n = 17) group to naphthalene, and a reference group ( n = 22) (Weiss et al 2020 ). The highly exposed group included employees directly exposed to naphthalene while mixing, sieving, moulding, or pressing naphthalene containing formulations.…”

1,2-dihydroxynaphthalene as Biomonitoring of Occupational Exposure to Naphthalene

“…According to some studies, the recommended biomonitoring of naphthalene exposure is 1and 2-naphthol in urine (Sams, 2017;Takeuchi et al, 2020;Weiss et al, 2020). However, there are several metabolites that can also be detected and used for biomonitoring of exposure.…”