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SECTION 1. CHEMICAL IDENTIFICATION

CHEMINFO Record Number: 264
CCOHS Chemical Name: Cyclohexane

Synonyms:
Benzene hexahydride
Hexahydrobenzene
Hexamethylene
Hexanaphthene

Chemical Name French: Cyclohexane
Chemical Name Spanish: Ciclohexano
CAS Registry Number: 110-82-7
UN/NA Number(s): 1145
RTECS Number(s): GU6300000
EU EINECS/ELINCS Number: 203-806-2
Chemical Family: Saturated alicyclic hydrocarbon / cycloalkane / cyclohexane
Molecular Formula: C6-H12

SECTION 2. DESCRIPTION

Appearance and Odour:
Colourless liquid with gasoline-like odour.(9)

Odour Threshold:
Wide range of values: 10.5-784 ppm (detection) (9); 25 ppm (1); 35 ppm (recognition) (9); 300 ppm (detection) (eye and mucous membrane irritation.(1)

Warning Properties:
NOT RELIABLE - Odour and irritation are not sufficient warning against exposure to hazardous concentrations.

Uses and Occurrences:
Solvent for fats, oils, waxes, resins and coatings; paint and varnish remover; extracting essential oils; production of nylon and numerous other chemicals and as a laboratory reagent.


SECTION 3. HAZARDS IDENTIFICATION

EMERGENCY OVERVIEW:
Colourless liquid with gasoline-like odour. EXTREMELY FLAMMABLE LIQUID AND VAPOUR. Can accumulate static charge. Vapour is heavier than air and may spread long distances and accumulate in low-lying areas. Distant ignition and flashback are possible. Liquid can float on water and may travel to distant locations and/or spread fire. Central nervous system depressant. High vapour concentrations may cause headache, nausea, dizziness, drowsiness, confusion, unconsciousness and death. Aspiration hazard. Swallowing or vomiting of the liquid may cause aspiration into the lungs.



POTENTIAL HEALTH EFFECTS

Effects of Short-Term (Acute) Exposure

Inhalation:
The acute toxicity is very low. In common with other alicyclic hydrocarbons, cyclohexane is a central nervous system depressant. Inhalation can cause headache, nausea, dizziness, drowsiness and confusion. Very high concentrations may cause unconsciousness and death. Vapour may be somewhat irritating to nose and throat, although relatively high concentrations can be tolerated without irritation to the mucous membranes.(5)

Skin Contact:
Direct contact with liquid may cause mild irritation. Based on animal studies, cyclohexane can be absorbed through the skin.(5)

Eye Contact:
Cyclohexane is not known as an eye irritant. Vapour may irritate the eyes. 300 ppm has been reported to be somewhat irritating to the eyes.(1) Splashes of liquid in the eyes may cause temporary irritation.

Ingestion:
Animal toxicity information indicates that cyclohexane has very low toxicity if ingested. Ingestion of extremely large doses may cause nausea, vomiting, diarrhea, headache and other symptoms of central nervous system depression, as described for "Inhalation" above. Cyclohexane can be readily aspirated into the lungs. Aspiration is the "breathing" of a material into the lungs when it is swallowed or vomited. Severe lung irritation, damage to lung tissues or death can result.
Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

Cyclohexane exposure has been associated with blood disorders but in these cases benzene exposure has also occurred, which would account for the blood changes.(4) No conclusions can be drawn about cyclohexane.

SKIN CONTACT: Cyclohexane dissolves skin oils. Undiluted cyclohexane causes skin irritation on prolonged contact.(5)

EFFECTS ON NERVOUS SYSTEM: Nerve damage of the extremities, such as the hands and feet (peripheral neuropathy) has been reported in workers exposed to petroleum solvlents containing mixtures of chemicals including cyclohexane.(13) A small number of workers exposed to low levels of cyclohexane at 28 ppm (range 5-211 ppm) for 1-2 years showed no evidence of neurotoxic effects when compared to controls.(14)

The nervous system effects of n-hexane have been well established and occur through a major metabolite (2,5-hexanedione).(15) Inhalation exposure studies with 8 volunteers found the major metabolites of cyclohexane to be cyclohexanediols.(16) While it is not possible to rule out neurotoxic effects from cyclohexane exposure, they are not expected from occupational exposure.

Carcinogenicity:

There is no human or animal information available.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human information available. No conclusions can be drawn from one animal study.

Reproductive Toxicity:
Insufficient information

Mutagenicity:
Positive results have been obtained in one study with cultured lymphocytes.(4) Negative results were obtained in bacteria.

Toxicologically Synergistic Materials:
Insufficient information

Potential for Accumulation:
Unlikely to accumulate since it is readily metabolized and excreted.


SECTION 4. FIRST AID MEASURES

Inhalation:
This product is extremely flammable. Take proper precautions (e.g. remove any sources of ignition). Remove source of contamination or move victim to fresh air. If breathing has stopped, trained personnel should begin artificial respiration or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately. Obtain medical attention immediately.

Skin Contact:
Remove contaminated clothing, shoes and leather goods (e.g., watchbands, belts). Wash gently and thoroughly with water and non-abrasive soap for at least 5 minutes or until the chemical is removed. If irritation persists, obtain medical advice immediately.

Eye Contact:
Quickly and gently blot or brush away excess chemical. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 5 minutes or until the chemical is removed, while holding the eyelid(s) open. Obtain medical advice immediately.

Ingestion:
Never give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If vomiting occurs naturally, have victim lean forward to reduce risk of aspiration. Repeat administration of water. Obtain medical attention immediately.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.

All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.



SECTION 5. FIRE FIGHTING MEASURES

Flash Point:
-20 deg C (-4 deg F) (closed cup) (10)

Lower Flammable (Explosive) Limit (LFL/LEL):
1.3% (10)

Upper Flammable (Explosive) Limit (UFL/UEL):
8% (10)

Autoignition (Ignition) Temperature:
245 deg C (473 deg F) (10)

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material.

Sensitivity to Static Charge:
Cyclohexane can accumulate static charge by flow or agitation due to its very low electrical conductivity (1.9 pS/m).(18) Vapour can be ignited readily by static discharge of sufficient energy. Minimum ignition energy: 0.22 millijoules.(18)

Fire Hazard Summary:
Extremely flammable liquid. Material will readily ignite at room temperature. Vapour is heavier than air and may travel a considerable distance to a source of ignition and flash back to a leak or open container. Liquid can float on water and may travel to distant locations and/or spread fire. Vapour can accumulate in confined spaces, resulting in a toxicity and flammability hazard. During a fire, irritating/toxic gases may be generated. Containers may explode in the heat of the fire.

Extinguishing Media:
Carbon dioxide, dry chemical powder, alcohol foam or polymer foam. Water may be ineffective because it may not cool the material below its flash point.(19) Fire fighting foams are the extinguishing agent of choice for most flammable liquid fires.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or protected location. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products.
Stop leak before attempting to stop the fire. If the leak cannot be stopped, and if there is no risk to the surrounding are, let the fire burn itself out. If the flames are extinguished without stopping the leak, vapours could form explosive mixtures with air and reignite.
Water can extinguish the fire if used under favourable conditions and when hose streams are applied by experienced firefighters trained in fighting all types of flammable liquid fires.
Containers may rupture in the heat of the fire. Isolate materials not yet involved in the fire and protect personnel. Move containers from fire area if this can be done without risk. Otherwise, fire-exposed containers or tanks should be cooled by application of hose streams and this should begin as soon as possible (within the first several minutes) and should concentrate on any unwetted portions of the container. If this is not possible, use unmanned monitor nozzles and immediately evacuate the area.
If a leak or spill has not ignited, use water spray in large quantities to disperse the vapours, to protect personnel attempting to stop a leak and to flush spills away from ignition sources. Solid streams of water may be ineffective and spread material.
For a massive fire in a large area, use unmanned hose holder or monitor nozzles; if this is not possible withdraw from fire area and allow fire to burn. Stay away from ends of tanks. Withdraw immediately in case of rising sound from venting safety device or any discolouration due to fire.
Firefighters may enter the area if positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) and full Bunker Gear is worn.



NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) HAZARD IDENTIFICATION

NFPA - Health: 1 - Exposure would cause significant irritation, but only minor residual injury.
NFPA - Flammability: 3 - Liquids and solids that can be ignited under almost all ambient temperature conditions.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.

SECTION 9. PHYSICAL AND CHEMICAL PROPERTIES

Molecular Weight: 84.16

Conversion Factor:
1 ppm = 3.44 mg/m3; 1 mg/m3 = 0.291 ppm at 25 deg C (calc.)

Physical State: Liquid
Melting Point: 6.6 deg C (44 deg F) (3)
Boiling Point: 81 deg C (178 deg F) (1,4,6)
Relative Density (Specific Gravity): 0.779 at 20 deg C (water = 1) (1,6)
Solubility in Water: Sparingly soluble (5.5 mg/100 mL at 20 deg C) (6)
Solubility in Other Liquids: Very soluble in ethanol, diethyl ether, acetone and benzene.(1,3)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = 3.44 (9)
pH Value: Not applicable
Vapour Density: 2.9 (air = 1) (5,6)
Vapour Pressure: 10.27 kPa (77 mm Hg) at 20 deg C (6,19)
Saturation Vapour Concentration: 101300 ppm (10.13%) at 20 deg C (calc.)
Evaporation Rate: 6.1 (butyl acetate = 1); 2.6 (diethyl ether = 1) (20)
Critical Temperature: 280.4 deg C (537 deg F) (20)

Other Physical Properties:
VISCOSITY-DYNAMIC: 1.02 mPa.s (1.02 centipoises) at 17 deg C (20)
VISCOSITY-KINEMATIC: 1.31 mm2/s (1.31 centistokes) at 17 deg C (calc.)
SAYBOLT UNIVERSAL VISCOSITY: Less than 32.6 seconds (3)
SURFACE TENSION: 24.6 mN/m (24.6 dynes/cm) (20)
CRITICAL PRESSURE: 4053 kPa (40 atm) (20)


SECTION 10. STABILITY AND REACTIVITY

Stability:
Normally stable

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.


STRONG OXIDIZING AGENTS (e.g. peroxides, nitrates and perchlorates) - may react violently. Increased risk of fire and explosion.(19)

Hazardous Decomposition Products:
None

Conditions to Avoid:
Heat, open flames, static discharge, sparks and other ignition sources.

Corrosivity to Metals:
Not corrosive


SECTION 11. TOXICOLOGICAL INFORMATION

LD50 (oral, 14-day old rat): 6200 mg/kg (cited as 8.0 mL/kg) (21)
LD50 (oral, young adult rat): 30400 mg/kg (cited as 39.0 mL/kg) (21)
LD50 (oral, older rat): 12850 mg/kg (cited as 16.5 mL/kg) (21)
LD50 (oral, mouse): 813 mg/kg (22, unconfirmed)

LD50 (dermal, rabbit): Greater than 18000 mg/kg (4)

Skin Irritation:

Cyclohexane was tested for irritancy on rabbit skin using different protocols. Depending on the protocol, cyclohexane was found to be either marginally a skin irritant or marginally not a skin irritant.(2) Repeated application to rabbit skin caused slight temporary irritation and thickening.(7)

Effects of Short-Term (Acute) Exposure:

Inhalation:
The primary effect of inhaling cyclohexane is depression of the central nervous system. The order of symptoms shown by experimental animals with increasing dosage is lethargy, prostration, increased respiration, convulsions, coma and finally death resulting from respiratory paralysis. Acute toxicity of inhaling cyclohexane is very low, but a narrow margin exists between narcosis and death. The minimum concentration of inhaling producing narcosis in mice was 14500 ppm for 2 hours. Mice tolerated exposure to 29000 ppm for 1 hour, but died within 15 minutes of exposure to 43600 ppm. The minimum lethal concentration for mice has been reported to be 112300 ppm.(4) Exposure of mice and rabbits to 18000 ppm produced trembling within 5-6 minutes, disturbed equilibrium within 15 minutes, recumbency (lying down) within 25 minutes in mice and within 30 minutes in rabbits, and finally death, in mice.(3,4) Rabbits survived a single 8-hour exposure of 18500 ppm (1.85%), but 26000 ppm was lethal after 1 hour. A concentration of 12600 ppm resulted in lethargy, narcosis, increased respiration rate and convulsions. A concentration of 3330 ppm caused no visible effects.(1)

Skin Contact:
Massive doses applied to rabbit skin resulted in slight changes in liver and kidneys.(3) Application of cyclohexane to the skin of rabbits produced changes similar to those following oral administration, indicating that cyclohexane can be absorbed through the skin. However, anesthesia was not observed. Toxic changes in the heart, liver and kidneys were found in the animals, in addition to chronic bronchitis and some vascular degeneration in the lungs. No deaths occurred.(7)

Ingestion:
The minimum lethal dose of cyclohexane in rabbits was reported to be 5.5-6.0 g/kg. Single oral doses of 1.0-5.5 g/kg in rabbits produced severe diarrhea within 1-1.5 hours. The respiratory rate increased considerably. All rabbits were lethargic, but no true narcosis or convulsions were noted.(7) Lethal oral doses in rabbits led to severe diarrhea, circulatory collapse and death without prominent central nervous system depression or anesthesia. Generalized vascular damage and collapse and liver and kidney damage were found in the dead rabbits.(7) Aspiration of 0.2 mL cyclohexane into the lungs killed 2 of 3 rats within 24 hours.(4)

Effects of Long-Term (Chronic) Exposure:

Inhalation:
No major toxic effects have been reported in long-term inhalation studies. No effects were observed in rabbits exposed to 434 ppm for 8 hrs/day for 26 weeks, in a monkey exposed to 1220 ppm for 6 hrs/day for 50 days and in rats exposed to 2550 ppm 10 hr/day, 6 days/week for 30 weeks.(4,5) Minor changes were observed in the liver and kidneys of rabbits exposed to 786 ppm cyclohexane for 50 periods of 6 hrs each.(1) No toxic changes were found in rabbit tissues after exposure for the same period at a concentration of 434 ppm (1.46 mg/L).(1) Exposure of rabbits to cyclohexane for 6-8 hr/day for 2-26 weeks produced deaths at 7445 ppm and higher. Convulsions, tremors, narcosis and paresis (partial paralysis of the legs) were noted. In addition, lethal concentrations produced eye irritation, salivation, lethargy, laboured breathing, and cyanosis prior to death.(4) Cyclohexane has not shown the neurological effects found with similar exposures to n-hexane. Rats were exposed intermittently to 1500 and 2500 ppm cyclohexane for 9-10 hr/day, 5 days/week for up to 30 weeks. No effect on body weight, peripheral neuropathy or pathological changes in the tibial nerves were seen.(4,9) Metabolic studies with rabbits have shown small amounts of a neurotoxic metabolite in urine.(16)

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
Exposure of pregnant mice to a solvent mixture including cyclohexane produced no external malformations in spite of very high concentrations used. Maternal death and reduced weight gain were reported.(17) No conclusions can be drawn from this study.


SECTION 16. OTHER INFORMATION

Selected Bibliography:
(1) Cyclohexane. In: Documentation of the threshold limit values and biological exposure indices. 6th ed. American Conference of Governmental Industrial Hygienists, 1991. p. 355-356
(2) National Institute for Occupational Safety and Health pocket guide to chemical hazards. National Institute for Occupational Safety and Health, June 1994. p. 82-83
(3) Cavender, F. Alicyclic hydrocarbons. In: Patty's industrial hygiene and toxicology. 4th edition. Volume II. Part B. Toxicology. Edited by G.D. Clayton et al. John Wiley and Sons, 1994. p. 1267-1274
(4) Longacre, S. Cyclohexane. In: Ethel Browning's toxicity and metabolism of industrial solvents. 2nd ed. Volume 1. Hydrocarbons. 2nd edition. Elsevier Science Publishers, 1987. p. 225-235
(5) API toxicological review : cyclohexane. 2nd ed. American Petroleum Institute, 1962
(6) Verschueren, K. Handbook of environmental data on organic chemicals. 3rd ed. Van Nostrand Reinhold Company, 1996. p. 565-567
(7) Treon, J.F., et al. The physiological response of rabbits to cyclohexane, methylcyclohexane, and certain derivatives of these compounds. I. Oral administration and cutaneous application. The Journal of Industrial Hygiene and Toxicology. Vol. 25, no. 6 (June 1943). p. 199-214
(8) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(9) Health-based recommended occupational exposure limits for cyclohexane. Dutch Expert Committee for Occupational Standards (Met Nederlandstalige samenvatting). CIP-Gegevens Koninklijke Bibliotheek, 1990
(10) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 325
(11) European Communities (EC). Commission Directive 2004/73/EC. Apr. 29, 2004
(12) Grant, W.M., et al. Toxicology of the eye. 4th edition. Charles C. Thomas, 1993. p. 1127-1128
(13) Valentini, F., et al. Does n-heptane cause peripheral neutoxicity? A case report in a shoemaker. Occupational Medicine. Vol. 44 (1994). p. 102-104
(14) Yuasa, J., et al. Investigation on neurotoxicity of occupational exposure to cyclohexane: a neurophysiological study. Occupational and Environmental Medicine. Vol. 53, no. 3 (1996). p. 174-179
(15) Perbellini, L, et al. Identification of the metabolites of n-hexane, cyclohexane, and their isomers in men's urine. Toxicology and Applied Pharmacology. Vol. 53 (1980). p. 220-229
(16) Mraz, J., et al. Markers of exposure to cyclohexane, cyclohexane and cyclohexanol: 1,2- and 1,4-cyclohexanediol. Clinical Chemistry. Vol. 40, no. 7 (1994). p. 1466-1468
(17) Tachi, N., et al. Fetotoxic effects of exposure to the vapor of organic solvents from a synthetic adhesive in mice. Environmental Contamination and Toxicology. Vol. 53 (1994). p. 471-478
(18) Chemical safety sheets: working safely with hazardous chemicals. Kluwer Academic Publishers, 1991. p. 250
(19) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 959C
(20) HSDB record for cyclohexane. Date of last revision: 96/09/04
(21) Kimura, E.T., et al. Acute toxicity and limits of solvent residue for sixteen organic solvents. Toxicology and Applied Pharmacology. Vol. 19 (1971). p. 699-704
(22) RTECS database record for cyclohexane. Last updated: 2000-12
(23) Occupational Safety and Health Administration (OSHA). Organic Vapors. In: OSHA Analytical Methods Manual. Revision Date: Oct. 31, 2001. Available at: <www.osha-slc.gov/dts/sltc/methods/toc.html>
(24) National Institute for Occupational Safety and Health (NIOSH). Hydrocarbons, BP 36-216 deg C. In: NIOSH Manual of Analytical Methods (NMAM(R)). 4th ed. Edited by M.E. Cassinelli, et al. DHHS (NIOSH) Publication 94-113. Aug. 1994. Available at: <www.cdc.gov/niosh/nmam/nmammenu.html>
(25) Jacobs, G., et al. Evaluation of the test method for skin irritation as prescribed by OECD and EEC. Journal of Toxicology. Cutaneous and Ocular Toxicology. Vol. 6, no. 3 (1987). p. 215-225
(26) CRCS Inc. Information review. Cyclohexane. TSCA Interagency Testing Committee. Date produced: July 16, 1984. EPA/OTS 40-8423031. NTIS/OTS0527468.

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.


Review/Preparation Date: 1997-03-13

Revision Indicators:
US transport 1998-03-01
Resistance of materials 1998-06-01
TLV-TWA 1999-03-01
EU Risk 2000-04-01
EU Comments 2000-04-01
TLV comments 2001-03-01
TDG 2002-05-27
PEL transitional comments 2003-10-30
PEL-TWA final 2003-10-30
Resistance of materials for PPE 2004-03-28
Bibliography 2004-11-29
EU classification 2004-11-29
EU safety 2004-11-29
Bibliography 2005-04-02
Sampling/analysis 2005-04-02
Passive Sampling Devices 2005-04-02
Bibliography 2006-04-26



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