OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR n

MSDS MSDS # 10020, N-Hexane from Phillips 66

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR n-HEXANE

http://www.osha.gov/SLTC/healthguidelines/n-hexane/recognition.html#healthhazard

also see http://www.osha.gov/SLTC/healthguidelines/n-hexane/index.html

INTRODUCTION

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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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.

SUBSTANCE IDENTIFICATION

* Formula

C(6)H(14)

* Structure

(For Structure, see paper copy)

* Synonyms

Hexane, hexyl hydride, normal hexane, dipropyl, Gettysolve-B

* Identifiers

1. CAS No.: 110-54-3

2. RTECS No.: MN9275000

3. DOT UN: 1208 27

4. DOT label: Flammable Liquid

* 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. 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

2. Boiling point (at 760 mm Hg): 68.9 degrees C (156 degrees F)

3. Specific gravity (water = 1): 0.66 at 20 degrees C (68 degrees F)

4. Vapor density: 2.97

5. Freezing point: -95 degrees C (-139 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): 124 mm Hg

7. Solubility: Slightly solubility in water; soluble in alcohol, acetone, ether, and chloroform.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Heat, sparks, or flame.

2. Incompatibilities: Contact of n-hexane with strong oxidizing agents should be avoided. Mixtures with dinitrogen tetraoxide may explode at 28 degrees C (82.4 degrees F).

3. Hazardous decomposition products: None reported.

4. Special precautions: None reported.

* 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].

The ACGIH limit is based on the risk of nervous system effects [ACGIH 1991, p. 754].

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].

2. Effects on Humans: n-Hexane is a narcotic agent; an irritant to the eyes, upper respiratory tract, and skin; and a neurotoxin. Exposure of humans to 5,000 ppm n-hexane for 10 minutes causes marked vertigo; exposure to 1,500 ppm results in headache and slight nausea [Hathaway et al. 1991; Clayton and Clayton 1982]. In industrial settings, exposure to levels exceeding 1,000 ppm have been reported to cause mild symptoms of narcosis [Hathaway et al. 1991]. Eye and upper respiratory tract irritation has been reported to occur in humans exposed to 880 ppm n-hexane for 15 minutes [Clayton and Clayton 1982]. Dermal contact with n-hexane results in immediate irritation characterized by erythema and hyperemia; exposed subjects developed blisters 5 hours following dermal exposure to n-hexane [Hathaway et al. 1991]. The neuropathic toxicity of n-n-hexane in humans is well documented; cases of polyneuropathy have typically occurred in humans chronically exposed to levels of n-hexane ranging from 400 to 600 ppm, with occasional exposures up to 2,500 ppm [Hathaway et al. 1991]. Distal symmetrical motor weakness is common in most cases; however, in severely affected individuals, motor weakness may extend to the pelvic and high musculature [Rom 1992]. Nerve biopsies in affected individuals show swelling of the nerve and thinning of the myelin sheath. Functional neurological disturbances usually progress for a few months after termination of exposure. Although recovery is expected to occur within a year, clinical polyneuropathy has been reported in some cases to remain after 2 years [Hathaway et al. 1991]. Blurred vision, restricted visual field, and optic nerve atrophy has been reported to occur in association with n-hexane-induced polyneuropathy. Twelve of 15 individuals working with hexane for 12 years were found to have abnormal color discrimination [Grant 1986].

* 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].

2. Chronic exposure: Long-term exposure to n-hexane may cause disturbances in sensation, muscle weakness, and distal symmetric pain in the legs. Clinical changes include muscle atrophy, decreased muscle strength, footdrop, numbness, prickling, and a tingling sensation in the arms and legs. Neurological investigations reveal decreased motor nerve conduction, neurogenic damage and swelling of peripheral nerves with thinning of the myelin sheath. These symptoms may get worse for 2 to 3 months after cessation of exposure. Changes in vision may also be a symptom of chronic exposure to n-hexane [Hathaway et al. 1991].