Synonyms: Naphthalin; Naphthaline; Naphthene

OSHA IMIS Code Number: 1810

Chemical Abstracts Service (CAS) Registry Number: 91-20-3

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: QJ0525000

Department of Transportation Regulation Number (49 CFR 172.101) and 2012 Emergency Response Guidebook [4 MB PDF, 392 pages]: 1334 133 (crude or refined); 2304 133 (molten)

NIOSH Pocket Guide to Chemical Hazards - Naphthalene: Physical description, chemical properties, potentially hazardous incompatibilities, and more

U.S. Environmental Protection Agency (EPA) Hazard Summary - Naphthalene: Uses, sources and potential exposure, acute and chronic health hazard information, and more

National Toxicology Program (NTP) carcinogenic classification: Reasonably anticipated to be a human carcinogen [144 KB PDF, 3 pages]

International Agency for Research on Cancer (IARC) carcinogenic classification: Group 2B [70 KB PDF, 21 pages] (possibly carcinogenic to humans)

EPA carcinogenic classification: Carcinogenic potential cannot be determined

EPA Inhalation Reference Concentration (RfC): 3x10^-3 mg/m³

Agency for Toxic Substances and Disease Registry (ATSDR) Inhalation Minimal Risk Level (MRL): 0.0007 ppm (chronic)

NIOSH Immediately Dangerous to Life or Health (IDLH) concentration: 250 ppm

Notes on Other Potential Health Effects and Hazards

1. EPA's oral reference dose (daily oral exposure likely to be without an appreciable risk of deleterious effects during a lifetime) for naphthalene is 0.02 mg/kg/day (EPA 2000).
2. At least one study has shown that exposure to naphthalene in the air at a workplace can lead to DNA strand breaks, which are often seen as a precursor to tumor formation (Marczynski et al. 2005).
3. There have been numerous reports of hemolytic anemia and cataracts following occupational exposure to naphthalene (ATSDR 1995).
4. Naphthalene in expired air has been studied as a biomarker of dermal and inhalational exposure to jet fuel, but the elimination in breath is fairly rapid, with a halftime of 19 to 25 minutes (Egeghy et al. 2003).
5. Occupational monitoring of naphthalene exposure usually involves the measurement of the urinary metabolites 1-naphthol and 2-naphthol (Preuss et al. 2003).
6. The EPA reference concentration is based on an inhalation study in mice in which hyperplasia and metaplasia in respiratory and olfactory epithelium, were observed  in nearly all the animals at 30 ppm, which was the lowest dose tested (EPA 1998).
7. The NTP classification of naphthalene as reasonably anticipated to be carcinogenic to humans, and the IARC classification as Group 2B, possibly carcinogenic to humans, was based on an inhalation bioassay in rats and mice (IARC 2002).

Date Last Revised: 12/11/2012

Literature Basis

• ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Naphthalene. 2001.
• ATSDR: Toxicological Profile for Naphthalene, 1-Methylnaphthalene and 2-Methylnaphthalene. 2005.
• Egeghy, P.P., Hauf-Cabalo, L., Gibson, R. and Rappaport, S.M.: Benzene and naphthalene in air and breath as indicators of exposure to jet fuel. Occup. Environ. Med. 60(12): 969-976, 2003.
• EPA IRIS Napthalene (1998)
• IARC Monographs on Evaluation of Carcinogenic Risks to Humans, Volume 82, Naphthalene, 2002
• Marczynski, B. et al.: Genotoxic risk assessment in white blood cells of occupationally exposed workers before and after alteration of the polycyclic aromatic hydrocarbon (PAH) profile in the production material: comparison with PAH air and urinary metabolite levels. Int Arch Occup Environ Health 78(2): 97-108, 2005.
• NIOSH: Occupational Health Guideline for Naphthalene. September 1978.
• NIOSH/IPCS: International Chemical Safety Cards - Naphthalene. April 21, 2005.
• National Toxicology Program (NTP). Toxicology and carcinogenesis studies of naphthalene in B6C3F1 mice (inhalation studies). Technical Report Series No. 410. NIH Publication No. 92-3141. (1992).
• NTP 12th Report on Carcinogens Napthalene, 2011 [144 KB PDF, 3 pages].
• Preuss, R., Angerer, J. and Drexler, H.: Naphthalene - an environmental and occupational toxicant. Int. Arch. Occup. Environ. Health 76(8): 556-576, 2003.

Laboratory Sampling/Analytical Method:

• sampling media: Chromosorb 106 Tube (100/50 mg sections, 60/80 mesh)
  analytical solvent: Carbon Disulfide
  maximum volume: 10 Liters
  maximum flow rate: 0.2 L/min (TWA)
  maximum volume: 3 Liters
  maximum flow rate: 0.2 L/min (STEL)
  current analytical method: Gas Chromatography; GC/FID
  method reference: OSHA Analytical Method (OSHA 35)
  method classification: Fully Validated
  note: Submit as a separate sample.

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