n-Hexane

2021-02-12

Hexane is an alkane of six carbon atoms, with the chemical formula C6H14. There are 5 hexane isomers; n-hexane is the unbranched isomer. [1] n-Hexane is a chemical made from crude oil. Pure n-hexane is a colourless liquid with a slightly disagreeable odour. It evaporates very easily into the air and dissolves only slightly in water. n-Hexane is highly flammable, and its vapours can be explosive. [2]

Uses [3]

Hexane is used in laboratories, primarily when it is mixed with similar chemicals to produce solvents. Common names for these solvents are commercial hexane, mixed hexanes, petroleum ether, and petroleum naphtha. The major use for solvents containing n-hexane is to extract vegetable oils from crops such as soybeans, flax, peanuts, and safflower seed. They are also used as cleaning agents in the textile, furniture, shoemaking, and printing industries, particularly rotogravure printing. N-hexane is also an ingredient of special glues that are used in the roofing, shoe, and leather industries. n-Hexane is used in binding books, working leather, shaping pills and tablets, canning, manufacturing tires, and making baseballs.

Sources of Emission & Routes of Exposure

Sources of Emission [3]

  • Industry sources: Releases from industries producing, using or handling hexane. For example, rubber and plastics products industries, oil refineries, chemical plants, footwear manufacturing, petrol, and paints and adhesives.
  • Diffuse sources: Releases from service stations; evaporation of fuels during petrol refilling; underground storage tanks that leak. Releases during use of adhesives, paints, and paint thinners.
  • Natural sources: Hexane is a natural constituent of crude petroleum. It also occurs naturally as a plant volatile and can be released from volcanoes. Furthermore, n-hexane occurs naturally in, forest fires, and some plants.
  • Transport sources: Vehicle exhaust. Evaporation of vehicle fuels from motors and vehicle fuel tanks.
  • Consumer products: Consumer products that contain small amounts of n-hexane include petrol, rubber cement, type-over correction fluids, non-mercury (low temperature) thermometers, alcohol preparations, and aerosols in perfumes. n-Hexane is also a component of preparations such as paint thinners, general-purpose solvents, degreasing agents, and cleaners.

Routes of Exposure [3,4]

n-Hexane evaporates very quickly and so the most common exposure is from breathing air-containing hexane. It can also enter via the skin. The most probable route of human exposure to hexane is by inhalation. Since it is in gasoline, nearly everyone is exposed to very small amounts of n-hexane in the air. Exposure can occur at home if you use products containing n-hexane without proper ventilation. Individuals are most likely to be exposed to hexane in the workplace. Monitoring data indicate that hexane is a widely occurring atmospheric pollutant.

Health Effects

Acute Effects

  • Acute inhalation exposure of humans to high levels of hexane causes mild CNS depression. CNS effects include dizziness, giddiness, slight nausea, and headache in humans.
  • Acute exposure to hexane vapours may cause dermatitis and irritation of the eyes and throat in humans.
  • Acute animal tests in rats have demonstrated hexane to have low acute toxicity from inhalation and ingestion exposure.

Chronic Effects

  • Chronic inhalation exposure to hexane is associated with sensorimotor polyneuropathy in humans, with numbness in the extremities, muscular weakness, blurred vision, headache, and fatigue observed.
  • Rats, chronically exposed by inhalation, have exhibited neurotoxic effects.
  • Mild inflammatory, erosive, and degenerative lesions in the olfactory and respiratory epithelium of the nasal cavity have been observed in mice chronically exposed by inhalation. Pulmonary lesions have also been observed in chronically exposed rabbits.
  • The Reference Concentration (RfC) for hexane is 0.2 milligrams per cubic metre (mg/m3) based on neurotoxicity in humans and epithelial lesions in the nasal cavity in mice.
  • EPA has not established a Reference Dose (RfD) for hexane.
  • EPA has calculated a provisional RfD of 0.06 milligrams per kilogram body weight per day (mg/kg/d) based on neurological and reproductive effects in rats.

Reproductive/Developmental Effects

  • No information is available on the reproductive or developmental effects of hexane in humans.
  • Testicular damage has been observed in male rats exposed to hexane via inhalation.
  • Teratogenic effects were not observed in the offspring of rats chronically exposed via inhalation in several studies.

Carcinogenicity

  • No information is available on the carcinogenic effects of hexane in humans or animals.
  • EPA has classified hexane as a Group D, not classifiable as to human carcinogenicity, based on a lack of data concerning carcinogenicity in humans and animals. (3,5)

Safety [6]

First Aid Measures

  • Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Get medical attention if irritation occurs.
  • Skin Contact: Wash with soap and water. Cover the irritated skin with an emollient. Get medical attention if irritation develops.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek medical attention.
  • Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention if symptoms appear.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention.
  • Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Loosen tight clothing such as a collar, tie, belt or waistband. Get medical attention if symptoms appear.

Fire and Explosion Information

  • n-Hexane is flammable.
  • Auto-ignition temperature is 225°C (437°F)
  • Flash Points: CLOSED CUP: -22.5°C (-8.5°F).
  • Carbon monoxide (CO) and carbon dioxide (CO2) are produced upon combustion.
  • Highly flammable in presence of open flames and sparks, of heat.
  • Non-flammable in presence of shocks.
  • n-hexane is a flammable liquid that is insoluble in water.
  • Dry chemical powder should be used to extinguish small fires
  • Water spray or fog should be used to extinguish large fires.
  • Special Remarks on Fire Hazards: Extremely flammable liquid and vapour. Vapour may cause flash fire.

Exposure Controls & Personal Protection

Engineering Controls

  • Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapours below their respective threshold limit value.
  • Ensure that eyewash stations and safety showers are proximal to the workstation location.

Personal Protective Equipment

The following personal protective equipment is recommended when handling n-hexane:

  • Safety glasses;
  • Lab coat;
  • Vapour respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves (impervious).

Personal Protection in Case of a Large Spill:

  • Splash goggles;
  • Full suit;
  • Vapour respirator;
  • Boots;
  • Gloves;
  • A self-contained breathing apparatus should be used to avoid inhalation of the product.
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Regulation

United States [4,7]

NIOSH: The National Institute of Occupational Safety and Health has established a Recommended Exposure Limit (REL) of no more than 50 parts per million (ppm) in workplace air or 180 mg/m3.

OSHA: The Occupational Health and Safety Administration has set a Permissible Exposure Limit of 500 ppm for n-hexane in workplace air or 1800 mg/m3).

EPA: The Environmental Protection Agency requires that spills or accidental releases of 5,000 pounds or more of n-hexane be reported to the EPA.

Australia [3]

Safe Work Australia has set a maximum 8-hour time weighted average (TWA) exposure for n-hexane of 176 mg/m3.

References

http://en.wikipedia.org/wiki/N-hexane

http://www.atsdr.cdc.gov/phs/phs.asp?id=391&tid=68

http://www.npi.gov.au/resource/n-hexane-sources-emissions

http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=392&tid=68

http://www.epa.gov/ttn/atw/hlthef/hexane.html

http://www.sciencelab.com/msds.php?msdsId=9927187