Disclaimer: These guidelines were developed under contract using generally accepted secondary sources. The protocol used by the contractor for surveying these data sources was developed by the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the Department of Energy (DOE). The information contained in these guidelines is intended for reference purposes only. None of the agencies have conducted a comprehensive check of the information and data contained in these sources. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The secondary sources used for supplements 111 and 1V were published before 1992 and 1993, respectively, and for the remainder of the guidelines the secondary sources used were published before September 1996. This information may be superseded by new developments in the field of industrial hygiene. Therefore readers are advised to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR DICHLORODIFLUOROMETHANE

INTRODUCTION

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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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

CCl(2)F(2)

* Structure

(For Structure, see paper copy)

* Synonyms

Refrigerant 12, freon 12, propellant 12, halon 122, difluorodichloromethane, FC 12, freon F-12.

* Identifiers

1. CAS No.: 75-71-8

2. RTECS No.: PA8200000

3. DOT UN: 1028 12

4. DOT label: Nonflammable gas

* Appearance and odor

Dichlorodifluoromethane is a colorless gas with a characteristic ether-like odor; it is pressurized and used in liquid form. At concentrations below 20 percent by volume, dichlorodifluoromethane has no odor.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 120.9

2. Boiling point (at 760 mm Hg): -29.8 degrees C (-21.6 degrees F)

3. Specific gravity (water = 1): 1.49 (at boiling point)

4. Vapor density: 4.2

5. Melting/Freezing point: -157.7 degrees C (-252 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): 4332 mm Hg

7. Solubility: Nearly insoluble in water; soluble in most organic solvents.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Heat.

2. Incompatibilities: Contact between dichlorodifluoromethane and chemically active metals such as sodium, potassium, calcium, powdered aluminum, zinc, and magnesium should be avoided.

3. Hazardous decomposition products: Toxic gases and vapors such as hydrogen chloride, phosgene, and hydrogen fluoride may be released in a fire involving dichlorodifluoromethane.

4. Special precautions: None reported.

* Flammability

BULLET TEXT = Dichlorodifluoromethane is nonflammable.

The National Fire Protection Association has not assigned a flammability rating to dichlorodifluoromethane.

1. Flash point: Not applicable.

2. Autoignition temperature: Not applicable.

3. Flammable limits in air: Not applicable.

4. Extinguishant: Use an extinguishant that is suitable for the materials involved in the surrounding fire.

Fires involving dichlorodifluoromethane 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. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Cylinders of dichlorodifluoromethane 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. 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 dichlorodifluoromethane.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for dichlorodifluoromethane is 1000 parts per million (ppm) parts of air (4950 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 dichlorodifluoromethane of 1000 ppm (4950 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 dichlorodifluoromethane a threshold limit value (TLV) of 1000 ppm (4950 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 18].

* Rationale for Limits

The NIOSH limit is based on the risk of narcotic effects and possible asphyxia from vapor [NIOSH 1992].

The ACGIH limit is based on the risk of cardiac sensitization and systemic injury [ACGIH 1991, p. 421].

HEALTH HAZARD INFORMATION

* Routes of Exposure Exposure to dichlorodifluoromethane can occur through inhalation and eye or skin contact [Sittig 1991].

* Summary of toxicology

1. Effects on Animals: Dichlorodifluoromethane is a narcotic at high concentrations and an asphyxiant at very high concentrations in experimental animals. The LC(50) in rats, rabbits, and guinea pigs for a 30-minute exposure is 800,000 ppm. Exposure to 600,000 ppm dichlorodifluoromethane for 2 hours caused death in rats but not in guinea pigs [ACGIH 1991; Sax and Lewis 1989]. Mice exposed to 10,000 ppm for 24 hours survived but sustained lung tissue alterations. In dogs, monkeys, and guinea pigs exposed to 200,000 ppm for 40 hours per week for 10 to 12 weeks, generalized tremor and other signs of narcosis were noted. Microscopic liver injury was noted in guinea pigs exposed to 810 ppm continuously for 90 days, although no such injury was observed among rats, rabbits, dogs, and monkeys similarly exposed. Cardiac arrhythmias were observed in 5 to 12 dogs exposed both the 50,000 ppm dichlorodifluoromethane and exogenous epinephrine. Constriction of the airways has been noted in animals exposed to 50,000 to 100,000 ppm [ACGIH 1991]. The effects of direct eye contact with liquefied dichlorodifluoromethane under pressure are usually minimal, unless the eyelids are prevented from shutting, in which case temporary freezing of the eye surface may occur. Damage from this type of severe exposure resolved within 3 days [Grant 1986].

2. Effects on Humans: In high concentrations, dichlorodifluoromethane can cause narcosis, unconsciousness, cardiac arrhythmias, cardiac arrest, and asphyxiation, either as a result of dichlorodifluoromethane's narcotic effects or as a consequence of its displacement of oxygen in the atmosphere. Many nonoccupational deaths have been reported from the sniffing of fluorochlorinated hydrocarbon aerosols, including dichlorodifluoromethane; the mechanism of action in these cases is believed to be cardiac arrhythmias caused by sensitization of the myocardium to epinephrine [Hathaway et al. 1991]. Studies in volunteers showed that inhalation of 10,000 ppm of dichlorodifluoromethane for 2.5 hours caused a 7 percent reduction in standardized psychomotor scores; however, at 1,000 ppm for 8 hours/day, 5 days/week, for a total of 17 repetitive exposures, no abnormal responses occurred [Clayton and Clayton 1982]. Exposure to 40,000 ppm for 8 minutes caused generalized sensory losses, ringing in the ears, apprehension, and slurred speech; at 110,000 ppm for 11 minutes, there were cardiac arrhythmias, amnesia, and a marked decrease in consciousness [Hathaway et al. 1991]. An individual exposed to 150,000 ppm experienced loss of consciousness [Parmeggiani 1983]. Individuals with cardiac or respiratory disorders may prove especially susceptible to dichlorodifluoromethane [NLM 1995]. Contact with the liquid can cause frostbite because of the rapid evaporation of this chemical [Sittig 1991].

* Signs and symptoms of exposure

1. Acute exposure: The most common symptoms of exposure to dichlorodifluoromethane are those associated with narcosis, which include dizziness, drowsiness, trembling, irregular heartbeat, unconsciousness, and, if the concentration is extremely high, death through asphyxiation. If liquefied dichlorodifluoromethane contacts the eyes or skin, pain, redness, and then whiteness of the affected tissue may occur if the contact was sufficiently severe to cause frostbite. Blistering may occur after tissue is thawed [Hathaway 1991].

2. Chronic exposure: No signs or symptoms of chronic exposure to dichlorodifluoromethane 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 dichlorodifluoromethane and lead to worker exposures to this substance:

* The manufacture and transportation of dichlorodifluoromethane

* Formerly used as aerosol propellants for cosmetics, pharmaceuticals, insecticides, paints, adhesives, and cleaners (almost all fluorochloro-carbon-propelled aerosol uses were banned by EPA in 1978); used as a refrigerant in home and commercial air conditioners; used as a rocket propellant; used to prepare frozen tissue sections

* Used as a blowing agent for cellular polymers; used as a low-temperature solvent or diluent in fumigants for food sterilization, and as a solvent or degreaser in paints and varnish removers and in polymerization processes

* Used as a foaming agent in fire extinguishing aerosols; used in immersion quick freezing of food products; used to chill cocktail glasses

* Used in water purification; copper and aluminum purification, petroleum recovery, and in manufacture of glass bottles

* Used in regulating devices for leak detection; used in thermal expansion valves; used as insulators and generator windings in manufacture of materials for electrical applications

* Used in organic synthesis of freons and resins; used as a working fluid for heat pumps and in hydraulic fluids

Methods that are effective in controlling worker exposures to dichlorodifluoromethane, 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.

MEDICAL SURVEILLANCE

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 dichlorodifluoromethane 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 dichlorodifluoromethane, 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 heart and central nervous system.

A preplacement medical evaluation is recommended to assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to dichlorodifluoromethane at or below the prescribed exposure limit. The health care professional should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the heart or central nervous system.

* 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 dichlorodifluoromethane exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of dichlorodifluoromethane on the heart or central 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. No biological monitoring test acceptable for routine use has yet been developed for dichlorodifluoromethane.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne dichlorodifluoromethane is made using two charcoal tubes in series (first tube 400/200 mg second tube 100/50 mg sections, both 20/40 mesh). Samples are collected at a maximum flow rate of 0.05 liter/minute until a maximum collection volume of 4 liters is reached. The sample is then treated with methylene chloride. 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 in NIOSH Method No. 1018 and is fully validated [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If liquified dichlorodifluoromethane contacts the skin, workers should flush the affected areas immediately with plenty of tepid water.

Clothing contaminated with dichlorodifluoromethane should be removed immediately and should not be reworn until the dichlorodifluoromethane has evaporated from the clothing.

A worker who handles dichlorodifluoromethane 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 dichlorodifluoromethane is handled, processed, or stored.

STORAGE

Dichlorodifluoromethane 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 dichlorodifluoromethane should be protected from physical damage and ignition sources, and should be stored separately from chemically active metals such as sodium, potassium, calcium, powdered aluminum, zinc, and magnesium should be avoided.

SPILLS AND LEAKS

In the event of a spill or leak involving dichlorodifluoromethane, 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 area of leak to disperse the gas.

4. If possible without risk, stop leak. Do not release leaking cylinder gas to the atmosphere because of CF-12's role in ozone depletion.

5. If leak cannot be repaired, empty into a combustion chamber with a combustible fuel and burn. Insure complete combustion to prevent phosgene formation.

6. Refer to local/state air pollution control authority before incineration.

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

Dichlorodifluoromethane 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].

The reportable quantity of dichlorodifluoromethane is 5,000 pounds. If an amount equal to or greater than this quantity is released within a 24-hour period in a manner that will expose persons outside the facility, employers are required to do the following: - Notify the National Response Center immediately at (800) 424-8802 or at (202) 426-2675 in Washington, D.C. [40 CFR 302.6].

* Community right-to-know requirements

Employers who own or operate facilities in SIC codes 20 to 39 that employ 10 or more workers and that manufacture 25,000 pounds or more of dichlorodifluoromethane per calendar year or otherwise use 10,000 pounds or more of dichlorodifluoromethane per calendar year are required by EPA [40 CFR Part 372.30] to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of dichlorodifluoromethane 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. Dichlorodifluoromethane is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. U075. It is approved for land disposal after treatment and only if the concentration of dichlorodifluoromethane in the waste or treatment residual does not exceed 7.2 mg/kg.

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 dichlorodifluoromethane 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 dichlorodifluoromethane. 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 dichlorodifluoromethane. The resistance of various materials to permeation by dichlorodifluoromethane is shown below:

To evaluate the use of these PPE materials with dichlorodifluoromethane, 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 dichlorodifluoromethane.

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.

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Grant WM [1986]. Toxicology of the eye. 3rd ed. Springfield, IL: Charles C Thomas.

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