Substance fact sheet
The National Pollutant Inventory (NPI) provides information on the types and amounts of pollutants being emitted in the Australian community.
This page provides facts about cyclohexane. It describes how you might be exposed to this substance, how exposure might effect you and the environment, common uses, comparative data about cyclohexane and its physical and chemical properties.
For more information about some of the terms used in this page, see the NPI glossary.
The National Pollutant Inventory (NPI) holds data for all sources of cyclohexane emissions in Australia.
Effects of cyclohexane on human health and the environment depend on how much cyclohexane is present and the length and frequency of exposure. Effects also depend on the health of a person or the condition of the environment when exposure occurs. Breathing large amounts of cyclohexane for short periods of time adversely affects the human nervous system. Effects range from headaches to anaesthesia, tremors, and convulsions. Contact with cyclohexane liquid or vapour can damage the eyes. These effects are not likely to occur at levels of cyclohexane that are normally found in the environment. Human health effects associated with breathing or otherwise consuming smaller amounts of cyclohexane over long periods of time are not known. Studies show that repeat exposure to large amounts of cyclohexane in air causes nervous system effects, eye damage, and respiratory effects in animals. The cyclohexane industry is now studying how its chemical affects the reproductive system and the development of the foetus of animals.
Cyclohexane enters the body when breathed in with contaminated air or when consumed with contaminated food or water. It can also be absorbed through skin contact. Cyclohexane is not likely to remain in the body due to its breakdown and removal in exhaled air and in urine.
Exposure to cyclohexane can occur in the workplace or in the environment following releases to air, water, land, or groundwater. Exposure can also occur when people use products that contain cyclohexane or when they smoke cigarettes.
See Sources for more information.
Worksafe Australia:
Maximum 8 hour time weighted average (TWA) exposure: 1,030 mg/m³
The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information.
Note that the emissions data in the NPI database is not directly comparable with these guidelines.
Cyclohexane is non-persistent in water, with a half-life of less than 2 days. The half-life of a pollutant is the amount of time it takes for one-half of the chemical to be degraded. Virtually 100% of cyclohexane will end up in the air.
The concentration of cyclohexane found in fish tissues is expected to be somewhat higher than the average concentration of cyclohexane in the water from which the fish was taken.
Cyclohexane has moderate acute toxicity to aquatic life. It has caused membrane damage in an ornamental crop species. Insufficient data are available to evaluate or predict the short-term effects of cyclohexane to birds or land animals.
Cyclohexane has moderate chronic toxicity to aquatic life. Insufficient data are available to evaluate or predict the long-term effects of cyclohexane to plants, birds, or land animals.
Cyclohexane enters the environment mainly in industrial and municipal discharges. Cyclohexane evaporates when exposed to air. It dissolves slightly when mixed with water. Most direct releases of cyclohexane to the environment are to air. Cyclohexane also evaporates from water and soil exposed to air. Once in air, it is expected to break down to other chemicals. Because it is a liquid that does not bind well to soil, cyclohexane that makes its way into the ground can move through the ground and enter groundwater. Plants and animals living in environments contaminated with cyclohexane can store small amounts of the chemical.
Cyclohexane by itself is not likely to cause environmental harm at levels normally found in the environment. Cyclohexane can contribute to the formation of photochemical smog when it reacts with nitrogen dioxide, ozone, and other volatile organic carbon substances in air.
No national guidelines.
This compound is used as a solvent to dissolve cellulose ethers, lacquers, resins, fats, waxes, oils, bitumen and crude rubber. It is also used in perfume manufacturing, during surface coating operations (lacquers), in synthesis of adipic acid for production of nylon 66 and engineering plastics, during synthesis of caprolactam in nylon 6, paint and varnish remover, in the extraction of essential oils, in analytical chemistry for molecular weight determinations, in the manufacturing of adipic acid, benzene, cyclohexyl chloride, nitrocyclohexane, cyclohexanol and cyclohexanone, in the manufacturing of solid fuel for camp stoves, in fungicidal formulations (possesses slight fungicidal action) in the industrial recrystallising of steroids, organic synthesis, recrystallising medium glass substitutes, solid fuels, in analytical chemistry and in manufacturing of adhesives.
The primary point sources are petroleum refining, automotive repair shops, and commercial printing and publishing.
Sub-threshold facilities.
Cyclohexane is a natural constituent of crude petroleum. It also occurs naturally as a plant volatile and can be released from volcanoes.
Cyclohexane has been detected in motor vehicle exhaust.
Cyclohexane is used as a solvent, oil extractant, paint and varnish remover, and in solid fuels.
Approximately 400 substances were considered for inclusion on the NPI reporting list. A ranking and total hazard score was given based on health and environmental hazards and human and environmental exposure to the substance.
Cyclohexane was ranked as 64 out of 400. The total hazard score taking into account both human health and environmental criteria is 2.2.
On a health hazard rating of 0 - 3 cyclohexane registers 0.7. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health.
On an environmental rating of 0 - 3 cyclohexane registers 1.5. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard.
Factors taken into account to obtain this ranking and these scores include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into account exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8. A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0.
| Substance name | Cyclohexane |
| CASR number | 110-82-7 |
| Molecular formula | C6H12 |
| Synonyms | hexamethylene; hexanaphthene; hexahydrobenzene, benzenehexahydride |
| Physical properties: Cyclohexane is a colourless, mobile liquid with a mild, sweet odour. It is slightly soluble in water and soluble in alcohol, acetone, benzene, ethanol, ethyl ether, olive oil, and carbon tetrachloride. Melting Point (°C): 6.47 Boiling Point (°C): 80.7 Specific Gravity: 0.779 Vapour Density: 2.98 1 ppm = 3.44 mg/m³ formula weight 84.161 |
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| Chemical properties: Cyclohexane is a flammable, non-corrosive liquid. |
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There is more information that may be useful in understanding some of the issues surrounding the NPI.