Naphthalene?an environmental and occupational toxicant

Abstract

For many years naphthalene had been considered as a non-carcinogenic polycyclic aromatic hydrocarbon (PAH). Airborne naphthalene concentrations have always been observed to be below the limit values of various national committees, such as the threshold limit value (TLV) of the American Conference of Governmental Industrial Hygienists (ACGIH) and the MAK of the Deutsche Forschungsgemeinschaft (DFG) (10 ppm). Since 2000, when the US National Toxicology Program revealed clear evidence of the carcinogenic activity of naphthalene in rats, international agencies [the International Agency for Research on Cancer (IARC), the US Environmental Protection Agency (US EPA), DFG] have reclassified naphthalene as a potential human carcinogen, and the European Union (EU) is currently preparing a new risk assessment report. It is presently unknown how to protect humans from health risks resulting from occupational and environmental naphthalene exposure. Knowledge about the external and internal exposure of humans serves as the key determinant in a comprehensive risk assessment. We review here ambient monitoring studies concerning the external naphthalene exposure that results from ubiquitous environmental sources (indoor and outdoor air, water, soil, food) and from a variety of critical workplaces (coking plants, creosote impregnation, distillation of coal tar and naphthalene, manufacture of refractories, graphite electrodes, aluminium and mothballs). Based on results of ambient monitoring studies published so far, a new hygiene-based exposure limit of 1.5 mg naphthalene per cubic metre of air (0.3 ppm) is proposed. Furthermore, results from biological monitoring studies are summarised in this article. The internal burden was almost exclusively determined by means of the urinary metabolites 1-naphthol and 2-naphthol, but it is currently not possible for one to evaluate a biological tolerance level (BAT) or a biological exposure index (BEI). Based on the toxicokinetics and metabolism of naphthalene, the central question on its carcinogenicity is briefly sketched. Naphthoquinones play an important role in this context. Their adducts with macromolecules may be the parameters of choice for the estimation of effects to human health.

Analysis of Urinary Metabolites of Polycyclic Aromatic Hydrocarbons in Incineration Workers

“…Hara and Itani 13) summarized the median 1OHP as ranging between 0.03 and 0.27 µmol/mol Cr (0.06 and 0.53 µg/gCr) for nonsmokers and between 0.07 and 0.76 µmol/mol Cr (0.14 and 1.5 µg/gCr) for smokers. Mean 2NP ranging between 1.1 and 2.2 µg/l for non-smokers and between 5.1 and 17.2 µg/l for smokers has been reported 10) . In the results of our study, 1OHP was relatively lower, while 2NP was almost the same as those of previous studies.…”

“…The reasons for measuring them are that their urinary concentrations are relatively high and their measurements are easier compared to those of carcinogenic PAHs, such as benzo [a]pyrene. Recently naphthalene was reclassified as being possibly carcinogenic to humans by IARC in 2002 10) . Consequently, the importance of measuring naphthalene metabolite levels has increased.…”

Simultaneous assessments of occurrence, ecological, human health, and organoleptic hazards for 77 VOCs in typical drinking water sources from 5 major river basins, China

“…Naphthalene is one of polycyclic aromatic hydrocarbons (PAHs), which was commonly detected in China (Guo et al, 2012;Liu and Zhou, 2011;Ma et al, 2014), while seldom detected in the USA (Carter et al, 2008;Moran et al, 2004;Rowe et al, 2007). For many years, naphthalene had been considered as a non-carcinogenic PAH, but in 2000, the US National Toxicology Program revealed clear evidence of the carcinogenic activity of naphthalene in rats (Preuss et al, 2003). Hexachlorobutadiene is used as solvent, heat transfer liquid, as well as hydraulic liquid.…”

“…Results showed that OHI values of common VOCs (data are not shown) except naphthalene in the Yellow River basin and the Liaohe River basin were far below 1, so common VOCs rarely cause taste and odor problems. Naphthalene have not only been classified as a potential human carcinogen (Preuss et al, 2003), but also as an odor of mothballs (Young et al, 1996). Aldehydes were often reported to be associated with fishy odor episode (Suffet et al, 2004;Watson et al, 2001;Zhao et al, 2013).…”

Radical scavenging effects of 1-naphthol, 2-naphthol, and their sulfate-conjugates

“…As noted earlier, 1-Nap and 2-Nap are often used as prototype substrates for some SULTs in Phase-II drug metabolism research (Allali-Hassani et al, 2007;Arand et al, 1987). In the human body, urinary Nap has been pro-posed as a biomarker for the exposure to carbaryl (carbamate insecticide; 1-naphthyl methylcarbamate) applied in a variety of crops (Sams, 2017), and for workers occupationally exposed to naphthalene (Preuss et al, 2003(Preuss et al, , 2004Sams, 2017). Sulfate conjugation of xenobiotics by SULTs may alter the physico-chemical properties of those compounds that are bioactive, and is widely assumed to result in the inactivation of their biological activity (Mulder and Jakoby, 1990;Falany and Roth, 1993;Weinshilboum and Otterness, 1994).…”