Biomonitoring Summary

Polycyclic Aromatic Hydrocarbons Overview


CAS No. 91-20-3

General Information

Naphthalene is produced commercially from coal tar and petroleum.It is used in producing an assortment of chemicals: phthalate plasticizers, naphthalene sulfonates and dyes, the insecticide carbaryl, and synthetic leather tanning chemicals. Naphthalene is an intermediate in manufacturing several pharmaceuticals. Crystalline naphthalene has been used as a moth repellent. Naphthalene is the most abundant PAH in cigarette smoke (Ding et al., 2005), and it is present in fossil fuel smoke and exhaust fumes, especially from diesel and jet fuels. Non-occupational exposure typically occurs through inhaling ambient and indoor air, and cigarette smoke. Naphthalene can be absorbed through the skin as a result of handling moth repellent or wearing clothes stored with moth repellent. Workers may be exposed via inhalation or dermal absorption in settings such as naphthalene production, coal coking operations, and wood treatment with creosote.

In the body, naphthalene metabolism is complex, leading to biologically reactive metabolites and other metabolites that are excreted in the urine. In studies of workers, naphthalene air concentrations were correlated with 1- and 2-hydroxynaphthalene urine concentrations (Bieniek 1994; 1997). Both naphthalene and the insecticide carbaryl are metabolized to 1-hydroxynaphthalene, making it difficult to distinguish between these exposures in the general population (Meeker et al., 2007). In contrast, only naphthalene metabolism results in 2-hydroxynaphthalene in urine.

Humans can develop hemolytic anemia and jaundice after high dose naphthalene exposure by either inhalation or ingestion, or from skin exposure to clothing and bedding treated with naphthalene moth repellents (ATSDR, 2005). Exposure to naphthalene vapor can irritate the eyes and respiratory tract. High dose and chronic exposure in occupational settings can result in cataracts or lens opacities (ATSDR, 2005). OSHA has established a workplace standard. IARC considers naphthalene to be a possible human carcinogen, and NTP considers that it is reasonably anticipated to be a human carcinogen.

Biomonitoring Information

Urinary levels of 1-hydroxynaphthalene and 2-hydroxynaphthalene (1-naphthol and 2-naphthol, respectively) reflect recent exposure. Levels similar to those reported in NHANES 2001–2002 and 2003–2004 subsamples have been found in small studies of pre-school children, adolescents and non-occupationally exposed adults (Kang et al., 2002; Kim et al., 2003; Kuusimaki et al., 2004; Wilson et al., 2003). Smokers typically have urinary 1- and 2-hydroxynaphthalene levels that are about 2 to 3 times higher than nonsmokers in both occupationally exposed and general populations (Campo et al., 2006; Nan et al., 2001; Serdar et al., 2003a, 2003b). Depending on the intensity of exposure, workers exposed to naphthalene have been found to have geometric mean urinary 1- and 2-hydroxynaphthalene levels that range from around 2 to 100 times higher than the levels in the Fourth Report (Bieniek 1997; Elovaara et al., 2006; Nan et al., 2001; Serdar et al., 2003a).

Finding a measurable amount of 1- or 2-hydroxynaphthalene in the urine does not imply that the level causes an adverse health effect. Biomonitoring studies on levels of 1- and 2-naphthalene provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of naphthalene than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.


Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene. August 2005 (update) [online] Available at URL: 5/26/09

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Campo L, Buratti M, Fustinoni S, Cirla PE, Martinotti I, Longhi O, et al. Evaluation of exposure to PAHs in asphalt workers by environmental and biological monitoring. Ann NY Acad Sci 2006;1076:405-420.

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Elovaara E, Mikkola J, Makela M, Paldanius B, Priha E. Assessment of soil remediation workers’ exposure to polycyclic aromatic hydrocarbons (PAH): Biomonitoring of naphthols, phenanthrols, and 1-hydroxypyrene in urine. Toxicol Lett 2006;162:158-163.

Kang JW, Cho SH, Kim H, Lee CH. Correlation of urinary 1-hydroxypyrene and 2-naphthol with total suspended particulates in ambient air in municipal middle-school students in Korea. Arch Environ Health 2002;57(4):377-382.

Kim YD, Lee CH, Nan HM, Kang JW, Kim H. Effects of genetic polymorphisms in metabolic enzymes on the relationships between 8-hydroxydeoxyguanosine levels in human leukocytes and urinary 1-hydroxypyrene and 2-naphthol concentrations. J Occup Health 2003;45(3):160-167.

Kuusimaki L, Peltonen Y, Mutanen P, Peltonen K, Savela K. Urinary hydroxy-metabolites of naphthalene, phenanthrene and pyrene as markers of exposure to diesel exhaust. Int Arch Occup Environ Health 2004;77(1):23-30.

Meeker JD, Barr DB, Serbar B, Rappaport SM, Hauser R. Utility of urinary 1-naphthol and 2-naphthol levels to assess environmental carbaryl and naphthalene exposure in an epidemiology study. J Expo Sci Eviron Epidemiol 2007;17(4):314-20.

Nan HM, Kim H, Lim HS, Choi JK, Kawamoto T, Kang JW, et al. Effects of occupation, lifestyle and genetic polymorphisms of CYP1A1, CYP2E1, GSTM1 and GSTT1 on urinary 1-hydroxypyrene and 2-naphthol concentrations. Carcinogenesis 2001;22(5):787-793.

Serdar B, Egeghy PP, Waidyanatha S, Gibson R, Rappaport SM. Urinary biomarkers of exposure to jet fuel (JP-8). Environ Health Perspect 2003a;111(14):1760-1764.

Serdar B, Waidyanatha S, Zheng Y, Rappaport SM. Simultaneous determination of urinary 1- and 2-naphthols, 3- and 9-phenanthrols, and 1-pyrenol in coke oven workers. Biomarkers 2003b;8(2):93-109.

Page last reviewed: April 7, 2017