Disclaimer: The information contained in these guidelines is intended for reference purposes only. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The information contained in these guidelines is current as of date of publication (September, 1996); recommendations may be superseded by new developments in the field of industrial hygiene. Readers are therefore advised to regard these recomendations as general guidelines and to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR THIONYL CHLORIDE

INTRODUCTION

This guideline summarizes pertinent information about thionyl chloride 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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

SOCl(2)

* Structure

(For Structure, see paper copy)

* Synonyms

Sulfurous dichloride, sulfurous oxychloride, thionyl dichloride, thionyl chloride, sulfur chloride oxide

* Identifiers

1. CAS No.: 7719-09-7

2. RTECS No.: XM5150000

3. DOT UN: 1836 39

4. DOT label: Corrosive

* Appearance and odor

Thionyl Chloride is a colorless to pale yellow or reddish, fuming, refractive liquid with a suffocating odor.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 118.96

2. Boiling point (at 760 mm Hg): 76 degrees C (169 degrees F)

3. Specific gravity: 1.638 at 20 degrees C (68 degrees F)

4. Vapor density: Data not available.

5. Melting point: -104.5 degrees C (-156.1 degrees F)

6. Vapor pressure at 21.4 degrees C (70.52 degrees F): 100 mm Hg

7. Solubility: Miscible with carbon tetrachloride, benzene, and chloroform.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Temperatures above 140 degrees C (284 degrees F) will decompose thionyl chloride. Contact between thionyl chloride and any form of moisture should be avoided because violent reactions may occur.

2. Incompatibilities: Contact between thionyl chloride and ammonia or other bases, moisture, and dimethyl sulfoxide should be avoided. Hydrogen gas may be evolved if thionyl chloride, moisture, and metals are in contact.

3. Hazardous decomposition products: Toxic gases such as sulfur dioxide, sulfur chloride, or hydrogen chloride may be released in a fire involving thionyl chloride.

4. Special precautions: None reported.

* Flammability

Thionyl chloride is not combustible.

The National Fire Protection Association has assigned a flammability rating of 0 (minimal fire hazard) to thionyl chloride.

1. Flash point: Data not available.

2. Autoignition temperature: Data not available.

3. Flammable limits in air: Data not available.

4. Extinguishant: For small fires use dry chemical or carbon dioxide. Flood fire area with water from a distance to fight large fires involving thionyl chloride.

Fires involving thionyl chloride should be fought upwind from the maximum distance possible. Isolate the leak or spill area immediately for at least 150 feet in all directions. Do not get a solid stream of water on spilled material. Keep unnecessary people away; isolate the hazard area and deny entry. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Violent reactions with water may occur. Vapors are an explosion and poison hazard indoors, outdoors, or in sewers. Containers of thionyl chloride 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. Firefighters should wear a full set of chemical protective clothing and self-contained breathing apparatus when fighting fires involving thionyl chloride.

EXPOSURE LIMITS

* OSHA PEL

The Occupational Safety and Health Administration (OSHA) does not currently regulate thionyl chloride.

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has assigned thionyl chloride a ceiling of 1 part per million (ppm) parts of air (5 milligrams per cubic meter (mg/m³)), which should not be exceeded during any part of the working exposure [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienine (ACGIH) has assigned thionyl chloride a ceiling limit value of 1 ppm (4.9 mg/m³), which should not be exceeded during any part of the working exposure [ACGIH 1994, p. 34].

* Rationale for Limits

The NIOSH limit is based on the risk of eye, skin, and mucous membrane irritation [NIOSH 1992].

The ACGIH limit is based on the risk of irritation associated with exposure to thionyl chloride or its decomposition products [ACGIH 1991, p. 1543].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to thionyl chloride can occur through inhalation, ingestion, and eye or skin contact.

* Summary of toxicology

1. Effects on Animals: The one hour LC(50) in rats is 500 ppm [ACGIH 1991]. A concentration of 17.5 ppm thionyl chloride was lethal to cats in twenty minutes [ACGIH 1991].

2. Effects on Humans: Thionyl chloride is a severe irritantin humans. A worker exposed to an unknown concentration of thionyl chloride following a battery explosion developed severe pulmonary edema and later died [ACGIH 1991]. The concentration of sulfur dioxide (a decomposition product of thionyl chloride) in the room was later estimated to be 17,000 ppm. Thionyl chloride vapors are highly irritating to the eyes, skin, and mucous membranes [ACGIH 1991]. This is thought to be the result of the formation of hydrogen chloride and sulfur dioxide that occurs when thionyl chloride reacts with moisture.

* Signs and symptoms of exposure

1. Acute exposure: Acute exposures to high concentration of thionyl chloride or its decomposition products may result in severe skin, eye, and mucous membrane irritation and respiratory effects including edema.

2. Chronic exposure: No signs or symptoms of chronic exposure to thionyl chloride have been reported in humans.

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 thionyl chloride and lead to worker exposures to this substance:

* The manufacture and transportation of thionyl chloride
* Use in herbicides, surfactants, drugs, vitamins, and dyestuffs [ACGIH 1991, p. 1543; NLM 1992]

Methods that are effective in controlling worker exposures to thionyl chloride, depending on the feasibility of implementation, are as follows:

* Process enclosure
* Local exhaust ventilation
* General dilution ventilation
* Personal protective equipment

Workers 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 [1992]. Industrial ventilation--a manual of recommended practice. 21st ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne thionyl chloride is made using a midget fritted glass bubbler (MFGB) containing 10 milliliters of deionized water. Samples are collected at a recommended flow rate of 1 liter/minute (ceiling) for a minimum collection time of 15 minutes. Analysis is conducted by ion chromatography. This method is described in the OSHA Computerized Information System [OSHA 1994] and is not yet validated.

PERSONAL HYGIENE PROCEDURES

If thionyl chloride contacts the skin, workers should immediately wash the affected areas with soap and water.

Clothing contaminated with thionyl chloride 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 thionyl chloride, particularly its potential for causing skin burns and corrosion.

A worker who handles thionyl chloride 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 thionyl chloride or a solution containing thionyl chloride is handled, processed, or stored.

STORAGE

Thionyl chloride 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 thionyl chloride should be protected from physical damage and contact with moisture and should be stored separately from ammonia or other bases, and dimethyl sulfoxide.

SPILLS AND LEAKS

In the event of a spill or leak involving thionyl chloride, persons not wearing protective equipment and fully-encapsulating, vapor-protective clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Do not touch the spilled material; stop the leak if it is possible to do so without risk.

2. Notify safety personnel.

3. Ventilate the area of the spill or leak.

4. Use water spray to reduce vapors; do not put water directly on the leak or spill area.

5. For small liquid spills, take up with sand or other noncombustible absorbent material and place into closed containers for later disposal or neutralization.

6. Keep combustibles away from spilled material.

7. Cleanup only under the supervision of an expert.

SPECIAL REQUIREMENTS

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

Thionyl chloride 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].

Employers are not required by the emergency release notification provisions in 40 CFR Part 355.40 to notify the National Response Center of an accidental release of thionyl chloride; there is no reportable quantity for this substance.

* 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 thionyl chloride 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 thionyl chloride 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.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

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 thionyl chloride 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 thionyl chloride. 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 thionyl chloride. There are no published reports on the resistance of various materials to permeation by thionyl chloride.

To evaluate the use of PPE materials with thionyl chloride, 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 thionyl chloride.

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.

REFERENCES

ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

DOT [1993]. 1993 Emergency response guidebook, guide 39. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

Genium [1988]. Material safety data sheet No. 86. Schenectady, NY: Genium Publishing Corporation.

Mickelsen RL, Hall RC [1987]. 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 [1991]. 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 [1986]. 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 [1991]. Registry of toxic effects of chemical substances: Thionyl chloride. 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 [1992]. 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 [1994]. NIOSH pocket guide to chemical hazards. 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. 94-116.

NLM [1992]. Hazardous substances data bank: Thionyl chloride. Bethesda, MD: National Library of Medicine.

OSHA [1994]. Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.

Parmeggiani L [1983]. Encyclopedia of occupational health and safety. 3rd rev. ed. Geneva, Switzerland: International Labour Organisation.

Sax NI, Lewis RJ [1989]. Dangerous properties of industrial materials. 7th ed. New York, NY: Van Nostrand Reinhold Company.

Sittig M [1991]. 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. [1983]. Windholz Index 10th ed. Rahway, NJ: Windholz & Company.