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This guideline summarizes pertinent information about n-hexane for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.
(For Structure, see paper copy)* Synonyms
Hexane, hexyl hydride, normal hexane, dipropyl, Gettysolve-B* Identifiers
1. CAS No.: 110-54-3* Appearance and odor
N-hexane is a colorless, volatile liquid with a mild, gasoline-like odor. Commercial n-hexane is a mixture of n-hexane isomers with a small amount of cyclopentane, pentane, and heptane isomers. Benzene may be present in concentrations ranging from one to six percent. (Note: The preceding sentence was reviewed by OSHA for data quality purposes in 2008. (Reference Table) Benzene contamination existed in the past at the percentage levels previously stated in many petroleum distillates but has now generally been reduced to less than 0.1%. The manufacturers' MSDS prepared according the requirements of the Hazard Communication Standard should be consulted for specific product and mixture hazard information.) Air odor threshold concentrations for n-hexane ranging from 65 to 130 parts per million (ppm) parts of air have been reported.CHEMICAL AND PHYSICAL PROPERTIES
* Physical data
1. Molecular weight: 86.1* Reactivity
1. Conditions contributing to instability: Heat, sparks, or flame.* Flammability
The National Fire Protection Association has assigned a flammability rating of 3 (severe fire hazard) to n-hexane.1. Flash point: -22 degrees C (-7 degrees F)
2. Autoignition temperature: 223 degrees C (437 degrees F)
3. Flammable limits in air (percent by volume): Lower, 1.1; upper, 7.5
4. Extinguishant: For small fires use dry chemical, carbon dioxide, water spray, or regular foam. Use water sprat, fog, or regular foam to fight large fires involving n-hexane.
Fires involving n-hexane should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. Isolate the area for 1/2 mile in all directions if a tank, rail car, or tank truck is involved in the fire. For a massive fire in a cargo area, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from the area and let the fire burn. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Vapors may travel to a source of ignition and flash back. Vapors are an explosion and poison hazard indoors, outdoors, or in sewers. Containers of n-hexane may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. If this is not possible, cool fire exposed containers from the sides with water until well after the fire is out. Do not get water inside the containers. Stay away from the ends of containers. Personnel should withdraw immediately if a rising sound from a venting safety device is heard or if there is discoloration of a container due to fire. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving n-hexane.EXPOSURE LIMITS
* OSHA PEL
The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for n-hexane is 500 ppm (1800 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration [29 CFR 1910.1000, Table Z-1].* NIOSH REL
The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for n-hexane of 50 ppm (180 mg/m(3)) as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].* ACGIH TLV
The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned n-hexane a threshold limit value (TLV) of 50 ppm (176 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 23].* Rationale for Limits
The NIOSH limit is based on the risk of skin and nervous system effects [NIOSH 1992].
HEALTH HAZARD INFORMATION
* Routes of Exposure
Exposure to n-hexane can occur through inhalation, ingestion, and eye or skin contact [Sittig 1991, p. 889].* Summary of toxicology
1. Effects on Animals: n-Hexane is a neurotoxin, a narcotic, and an irritant of the eyes, skin, and mucous membranes [Hathaway et al. 1991]. n-Hexane also causes productive and embryotoxic effects and is cytotoxic in mammalian and human test systems [NIOSH 1991]. The oral LD(50) in rats is 28,710 mg/kg, and the lowest lethal concentration in mice is 120 g/m(3) [NIOSH 1991]. Mice exposed to concentrations ranging from 1,000 to 2,000 ppm 24 hours/day for 6 days/week for 1 year developed atrophy and degeneration of hind leg muscle fibers [NLM 1992]. Mice exposed to 2,500 to 3,000 ppm n-hexane for 4 days developed liver enlargement within 24 hours of exposure onset [NLM 1992]. Rabbits exposed by inhalation to 3,000 ppm 8 hours/day for 8 days showed changes in the lungs, emphysema, necrosis of the bronchial epithelium, and atelectasis [NLM 1992]. Rats continuously exposed to 400 ppm developed anoxapathy, although intermittent exposure to 10,000 ppm 6 hours/day, 5 days/week for 13 weeks caused only mild paranodol axonal swelling [Hathaway et al. 1991]. The offspring of rats and mice exposed orally or by inhalation to n-hexane during gestation showed depressed weight gain after birth [Hathaway et al. 1991]. This agent also affects male and female reproductive capacity [Amdur 1991].* Signs and symptoms of exposure
1. Acute exposure: Acute exposure to n-hexane may cause dizziness, confusion, nausea, headache, and irritation of the eyes, nose, throat, and skin [Hathaway et al. 1991].EMERGENCY MEDICAL PROCEDURES
* Emergency medical procedures: [NIOSH to supply]
5. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard [29 CFR 1910.1200]). All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.EXPOSURE SOURCES AND CONTROL METHODS
The following operations may involve n-hexane and lead to worker exposures to this substance:
* The manufacture and transportation of n-hexaneMethods that are effective in controlling worker exposures to n-hexane, depending on the feasibility of implementation, are as follows:
* Process enclosureWorkers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR 1910.120].
Good sources of information about control methods are as follows:
1. ACGIH . Industrial ventilation--a manual of recommended practice. 21st ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
2. Burton DJ . Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
3. Alden JL, Kane JM . Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.
4. Wadden RA, Scheff PA . Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.
5. Plog BA . Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.
OSHA is currently developing requirements for medical surveillance. When these requirements are promulgated, readers should refer to them for additional information and to determine whether employers whose employees are exposed to n-hexane are required to implement medical surveillance procedures.
* Medical Screening
Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical surveillance program is intended to supplement, not replace, such measures. To detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the term of employment, and (3) at the time of job transfer or termination.* Preplacement medical evaluation
Before a worker is placed in a job with a potential for exposure to n-hexane, a licensed health care professional should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the skin, respiratory system, central nervous system, and peripheral nervous system. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American Thoracic Society.* Periodic medical evaluations
Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to n-hexane exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of n-hexane on the skin, respiratory system, central nervous system, or peripheral nervous system. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.* Termination medical evaluations
The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population.* Biological monitoring
Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. Exposure to n-hexane can be measured in the exhaled air (as n-hexane) or in urine as the 2,5-hexanedione. The biological exposure index for n-hexane in urine is 5 grams 2,5-hexanedione/gram creatinine.WORKPLACE MONITORING AND MEASUREMENT
Determination of a worker's exposure to airborne n-hexane is made using a charcoal tube (100/50 mg sections, 20/40 mesh). Samples are collected at a maximum flow rate of 0.2 liter/minute (TWA) until a maximum collection volume of 4 liters is reached. The sample is then treated with 99:1 carbon disulfide:dimethylformamide. Analysis is conducted by gas chromatography using a flame ionization detector (GC/FID). This method is described in the OSHA Computerized Information System [OSHA 1994] and is fully validated. NIOSH Method No. 1500 for hydrocarbons with boiling point ranges from 36 to 126øC (96.8 to 258.9øF) can also be used to determine a worker's airborne exposure to n-hexane. This method is the reference method for the OSHA method described above and differs only in its use of carbon disulfide as the solvent used to extract the sample [NIOSH 1994].
PERSONAL HYGIENE PROCEDURES
If n-hexane contacts the skin, workers should immediately wash the affected areas with large amounts of soap and water.
Clothing contaminated with n-hexane should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of n-hexane, particularly its potential for causing irritation and nervous system effects.
A worker who handles n-hexane should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, using toilet facilities, applying cosmetics, or taking medication.
Workers should not eat, drink, use tobacco products, apply cosmetics, or take medication in areas where n-hexane or a solution containing n-hexane is handled, processed, or stored.
n-Hexane should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of n-hexane should be protected from physical damage and should be stored separately from strong oxidizing agents.
SPILLS AND LEAKS
In the event of a spill or leak involving n-hexane, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:
1. Notify safety personnel.
2. Remove all sources of heat and ignition.
3. Ventilate potentially explosive atmospheres.
4. Do not touch the spilled material; stop the leak if it is possible to do so without risk.
5. Use non-sparking tools.
6. Water spray may be used to disperse vapors.
7. For small liquid spills, take up with sand, earth, vermiculite, or other noncombustible absorbent material and place into closed containers for later disposal.
8. Keep n-hexane out of a confined space, such as a sewer, because of the possibility of an explosion, unless the sewer is designed to prevent the build-up of explosive concentrations.
9. For large liquid spills, build dikes far ahead of the spill to contain the n-hexane for later reclamation or disposal.
U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available.
* Emergency planning requirements
n-Hexane is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III) in 42 USC 11022.* Reportable quantity requirements for hazardous releases
A hazardous substance release is defined by EPA as any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of contaminated containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required to notify the proper Federal, State, and local authorities [40 CFR 355.40].* Community right-to-know requirements
Employers are not required by EPA in 40 CFR Part 372.30 to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of n-hexane emitted or released from their facility annually.* Hazardous waste management requirements
EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Although n-hexane is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above.RESPIRATORY PROTECTION
* Conditions for respirator use
Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of n-hexane exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergencies. Workers should only use respirators that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).* Respiratory protection program
Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].PERSONAL PROTECTIVE EQUIPMENT
Workers should use appropriate personal protective clothing and equipment that must be carefully selected, used, and maintained to be effective in preventing skin contact with n-hexane. The selection of the appropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to n-hexane. The resistance of various materials to permeation by n-hexane is shown below:
(*) Material estimated (but not tested) to provide at least four hours of protection.
(**) Not recommended, degradation may occur
To evaluate the use of these PPE materials with n-hexane, users should consult the best available performance data and manufacturers' recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components.
Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve n-hexane.
Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, caustic, or other toxic substance may be splashed into the eyes.
In addition to the possible need for wearing protective outer apparel (e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk.
Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness.
Protective clothing may interfere with the body's heat dissipation, especially during hot weather or during work in hot or poorly ventilated work environments.
ACGIH . Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
ACGIH . 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
Amoore JE, Hautala E . Odor as an aid to chemical safety: odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. J of App Tox 3(6):272-290.
ATS . Standardization of spirometry -- 1987 update. American Thoracic Society. Am Rev Respir Dis 136:1285-1296.
CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.
Clayton G, Clayton F [1981-1982]. Patty's industrial hygiene and toxicology. 3rd rev. ed. New York, NY: John Wiley & Sons.
DOT . 1993 Emergency response guidebook, guide 27. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.
Forsberg K, Mansdorf SZ . Quick selection guide to chemical protective clothing. New York, NY: Van Nostrand Reinhold.
Genium [1992. Material safety data sheet No.397. Schenectady, NY: Genium Publishing Corporation.
Grant WM . Toxicology of the eye. 3rd ed. Springfield, IL: Charles C Thomas.
Grayson M . Kirk-Othmer concise encyclopedia of chemical technology. Abridged version, 3rd ed. New York, NY: John Wiley & Sons.
Hathaway GJ, Proctor NH, Hughes JP, and Fischman ML . Proctor and Hughes' chemical hazards of the workplace. 3rd ed. New York, NY: Van Nostrand Reinhold.
Amdur MO, Doull J, Klaasen CD . Casarett and Doull's toxicology. 4th ed. New York, NY: McGraw-Hill, Inc.
Lide DR . CRC handbook of chemistry and physics. 73rd ed. Boca Raton, FL: CRC Press, Inc.
Mickelsen RL, Hall RC . A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.
Mickelsen RL, Hall RC, Chern RT, Myers JR . Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.
NFPA . Fire protection guide on hazardous materials. 9th ed. Quincy, MA: National Fire Protection Association.
NIOSH [1987a]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-116.
NIOSH [1987b]. NIOSH respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-108.
NIOSH . Registry of toxic effects of chemical substances: Hexane. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.
NIOSH . Recommendations for occupational safety and health: Compendium of policy documents and statements. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 92-100.
NIOSH . NIOSH manual of analytical methods. 4th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113.
NJDH . Hazardous substance fact sheet: Hexane. Trenton, NJ: New Jersey Department of Health.
NLM . Hazardous substances data bank: Hexane. Bethesda, MD: National Library of Medicine.
OSHA . Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.
Parmeggiani L . Encyclopedia of occupational health and safety. 3rd rev. ed. Geneva, Switzerland: International Labour Organisation.
Rom WN . Environmental and occupational medicine. 2nd ed. Boston, MA: Little, Brown and Company.
Sittig M . Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications.
USC. United States code. Washington. DC: U.S. Government Printing Office.
Windholz M, ed. . Merck Index 10th ed. Rahway, NJ: Merck & Company.