Synonyms: Benzene hexahydride; Hexahydrobenzene; Hexamethylene; Hexanaphthene

OSHA IMIS Code Number: 0810

Chemical Abstracts Service (CAS) Registry Number: 110-82-7

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: GU6300000

Department of Transportation Regulation Number (49 CFR 172.101) and 2012 Emergency Response Guidebook [4 MB PDF, 392 pages]: 1145 128

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

National Toxicology Program (NTP) carcinogenic classification: Not listed

International Agency for Research on Cancer (IARC) carcinogenic classification: Not listed

U.S. Environmental Protection Agency (EPA) carcinogenic classification: Data is inadequate for an assessment of human carcinogenic potential

EPA Inhalation Reference Concentration (RfC): 6 mg/m³

Agency for Toxic Substances and Disease Registry (ATSDR) Inhalation Minimal Risk Level (MRL): Not established

NIOSH Immediately Dangerous to Life or Health (IDLH) concentration: 1,300 ppm (10% LEL)

Notes on Other Potential Health Effects and Hazards

1. Vapor/air mixtures are explosive. Heating will cause a rise in pressure and a risk of bursting (NIOSH/IPCS 2008).
2. Highly flammable (NIOSH/IPCS 2008).
3. In human volunteers exposed to ~300 ppm of cyclohexane for 8 hours, the major urinary metabolites were 1,2- and 1,4-cyclohexanediol and their glucuronide conjugates. The mean elimination half-lives of these metabolites ranged from 16 to 17 hours (Mráz et al. 1998).  
4. In contrast, workers exposed to lower airborne levels of cyclohexane from glues (geometric mean: 27 ppm) showed a 16-hour between-shift decrease in urinary cyclohexanol, from 876 to 96 µg/liter, yielding an estimated biological half-life of approximately 5 hours (Yasugi et al. 1994).
5. EPA reference concentration established based on a two generation laboratory reproductive and developmental toxicity study resulting in reduced body weight in offspring and effects on hearing. (EPA 2003)

Date Last Revised: 11/16/2012

Literature Basis:

• ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Cyclohexane. 2002.
• EPA Cyclohexane (CASRN 110-82-7), 2003
• EPA Toxicological Review of Cyclohexane in Support of IRIS listing, 2003 [476 KB PDF, 87 pages]
• Kreckmann, KH; Baldwin, JK; Roberts, LG; et al. (2000) Inhalation developmental toxicity and reproduction studies with cyclohexane. Drug Chem Toxicol 23(4):555-73.
• Mráz, J. Gálová, E., Nohová, H. and Vítková, D.: 1,2- and 1,4-Cyclohexanediol - major urinary metabolites and biomarkers of exposure to cyclohexane, cyclohexanone, and cyclohexanol in humans. Int. Arch. Occup. Environ. Health 71(8): 560-565, 1998.
• NIOSH: Occupational Health Guideline - Cyclohexane. 1978.
• NIOSH/IPCS: International Chemical Safety Cards - Cyclohexane. April 10, 2008.
• Yasugi, T. et al.: Exposure monitoring and health effect studies of workers occupationally exposed to cyclohexane vapor. Int. Arch. Occup. Environ. Health 65(5): 343-350, 1994.

Laboratory Sampling/Analytical Method:

• sampling media: Charcoal Tube (100/50 mg sections, 20/40 mesh)
  analytical solvent: Carbon disulfide
  alternate analytical solvent: (99:1) Carbon Disulfide:Dimethylformamide
  maximum volume: 5 Liters
  maximum flow rate: 0.2 L/min
  current analytical method: Gas chromatography; GC/FID
  method reference: NIOSH Analytical Method (NIOSH 1500 [127 KB PDF, 8 pages])
  method classification: Partially Validated

** All Trademarks are the property of their respective owners.

Accessibility Assistance: Contact the OSHA Directorate of Technical Support and Emergency Management at (202) 693-2300 for assistance accessing PDF materials.