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 This information may be superseded by new developments in the field of industrial hygiene.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 DIAZOMETHANE

INTRODUCTION

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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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

CH(2)N(2)

* Structure

(For Structure, see paper copy)

* Synonyms

Azimethylene, diazirine, azomethylene

* Identifiers

1. CAS No.: 334-88-3

2. RTECS No.: PA7000000

3. Specific DOT number: None

4. Specific DOT label: None

* Appearance and odor

Diazomethane is a yellow gas with a musty odor. When stored under pressure, diazomethane is liquid in form.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 42

2. Boiling point (at 760 mm Hg): -23 degrees C (-9 degrees F)

3. Specific gravity (water = 1): 1.45 at 20 degrees C (68 degrees F)

4. Vapor density (air = 1): 1.45

5. Melting point: -145 degrees C (-229 degrees F)

6. Vapor pressure: Data not available.

7. Solubility: Decomposes in water; soluble in dioxane, ether, benzene, alcohol.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Diazomethane gas may explode violent, even if it is diluted with nitrogen. Heat, high-intensity light, shock, or contact with rough surfaces may cause diazomethane to explode; a highly concentrated or undiluted solution of liquid diazomethane may explode violently, especially if impurities are present.

2. Incompatibilities: Contact between diazomethane and alkali metals, calcium sulfate, calcium chloride, boiling stones, or copper powder will cause explosions.

3. Hazardous decomposition products: Toxic gases and vapors such as nitrogen oxide may be released in a fire involving diazomethane.

4. Special precautions: Barriers or shields should be used to protect employees from accidental explosions.

* Flammability

The National Fire Protection Association has not assigned a flammability rating to diazomethane; however, diazomethane poses an extreme explosion risk.

1. Flash point: Data not available.

2. Autoignition temperature: Explodes at 100degreesC (212 degrees F) or if impurities are present, at lower temperatures. Vapor may explode at temperatures above 200 degrees C (392 degrees F).

3. Flammable limits in air: Data not available.

4. Extinguishant: Diazomethane is highly flammable and explosive. For small fires use water spray, carbon dioxide, or regular foam. Use water spray, fog, or regular foam to fight large fires involving diazomethane.

Fires involving diazomethane should be fought upwind from the maximum distance possible. Diazomethane will explode in a fire. The fire area should be evacuated immediately. Keep unnecessary people away; isolate the hazard area and deny entry. 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 diazomethane 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. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving diazomethane.

EXPOSURE LIMITS

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for diazomethane is 0.2 parts per million (ppm) parts of air (0.4 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 diazomethane of 0.2 ppm (0.4 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 diazomethane a threshold limit value (TLV) of 0.2 ppm (0.34 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 severe respiratory irritation and sensitization, asthma attacks, and eye and mucous membrane irritation [NIOSH 1992].

The ACGIH limit is based on the risk of respiratory irritation and other toxic effects [ACGIH 1991, p. 391].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to diazomethane can occur through inhalation, ingestion, and eye or skin contact [Sittig 1991].

* Summary of toxicology

1. Effects on Animals: Diazomethane is a severe pulmonary irritant and a carcinogen and teratogen in laboratory animals; it is also mutagenic in bacteria [Parmeggiani 1983; Clayton and Clayton 1981]. Death caused by exposure to diazomethane is a result of damage to the respiratory system; mortality may be delayed for several days after exposure [Grant 1986; Hathaway et al. 1991]. Inhalation exposure caused pulmonary edema, hemorrhagic emphysema, and bronchopneumonia in exposed cats, rabbits, and guinea pigs [Hathaway et al. 1991]. In guinea pigs, repeated applications of diazomethane in a cottonseed oil or dioxane vehicle caused skin sensitization [Clayton and Clayton 1981]. Pregnant rats exposed for 30 minutes to diazomethane by inhalation produced dead and growth-retarded pups [Parmeggiani 1983]. Animal studies provide limited supporting evidence for the carcinogenic risk of diazomethane. Mice receiving skin applications of liquid diazomethane 5 times/week for 5 months developed lung adenomas. Rats exposed for 4.5 to 6 months to diazomethane gas developed pulmonary adenomas and squamous-cell carcinoma [ACGIH 1991].

2. Effects on Humans: Diazomethane is a potent respiratory tract irritant and allergen that causes, even in very low concentrations, coughing, fever, fulminating pneumonia, and death. Exposure can lead to hypersensitivity, manifested as asthma and fever [Parmeggiani 1983]. Two persons exposed to unspecified concentrations of diazomethane developed dizziness, headache, chest pain, fever, and severe asthmatic symptoms beginning about 5 hours after exposure. Other exposures have resulted in cyanosis, pulmonary edema, weakness, chest pain, pneumonia, and death [ACGIH 1991]. Hepatic enlargement and hemolysis are also reported to result from exposure to diazomethane. Diazomethane is irritating to the eyes and could cause serious ocular damage [Grant 1986]. Diazomethane also causes denudation of the skin and mucous membranes [Clayton and Clayton 1981]. Studies suggest that diazomethane is carcinogenic in mice and rats. The International Agency for Research on Cancer (IARC) concluded that diazomethane is not classifiable in terms of its carcinogenicity to humans [IARC 1987].

* Signs and symptoms of exposure

1. Acute exposure: Inhalation of diazomethane causes dizziness, headache, irritating cough, fever, fatigue, chest pain, shortness of breath, difficult breathing, and wheezing. Liver enlargement and hemolysis may also occur. Diazomethane causes eye irritation, burning, pain, tearing, and serious burns of the cornea. Exposure of the skin and mucous membranes may lead to burns and loss of skin or membrane.

2. Chronic exposure: Chronic exposure to diazomethane can produce pulmonary hypersensitivity that recurs on subsequent exposure, hepatic enlargement, and hemolysis.

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 diazomethane and lead to worker exposures to this substance:

* The manufacture and transportation of diazomethane

* Prepared on site for use as a methylating agent in chemical analysis and in laboratory organic synthesis

Methods that are effective in controlling worker exposures to diazomethane, 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 diazomethane 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 diazomethane, 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 eyes, skin, and respiratory tract. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American Thoracic Society.

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 diazomethane 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 eyes, skin, or respiratory tract.

* 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 diazomethane exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of diazomethane on the eyes, skin, or respiratory tract. 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 diazomethane.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne diazomethane is made using a coated XAD-2 tube (100/50 mg sections, 20/50 mesh). Coating is 1 percent (w/w) octanoic acid. Samples are collected at a maximum flow rate of 0.2 liter/minute until a maximum collection volume of 30 liters is reached. The sample is then treated with carbon disulfide. Analysis is conducted by gas chromatography using a flame ionization detector (GC/FID). This method (NIOSH # 2515) is described in the OSHA Computerized Information System [OSHA 1994] and the NIOSH Manual of Analytical Methods [NIOSH 1994b] and is fully validated.

PERSONAL HYGIENE PROCEDURES

If diazomethane contacts the skin, workers should flush the affected areas immediately with plenty of water, followed by washing with soap and water.

Clothing contaminated with diazomethane 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 diazomethane, particularly its potential for causing severe irritation.

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

STORAGE

Diazomethane 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 diazomethane should be protected from shock, heat, sparks, open flames and physical damage and should be stored separately from alkali metals, calcium sulfate, calcium chloride, boiling stones, or copper powder. Outside or detached storage is preferred. Empty containers of diazomethane should be handled appropriately.

SPILLS AND LEAKS

In the event of a spill or leak involving diazomethane, 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. Provide and require the use of fully-encapsulating, vapor-protective clothing and equipment for cleanup personnel.

5. If possible without risk, stop flow of gas. If source of leak is a cylinder and cannot be stopped in place, remove the leaking cylinder to a safe place in the open air, and repair leak or allow cylinder to empty.

6. If the leak is in the liquid form, allow diazomethane to evaporate.

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

Diazomethane 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 diazomethane is 1 pound. 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 diazomethane per calendar year or otherwise use 10,000 pounds or more of diazomethane 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 diazomethane 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 diazomethane 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 diazomethane 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 diazomethane. 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 diazomethane. There are no published reports on the resistance of various materials to permeation by diazomethane.

To evaluate the use of PPE materials with diazomethane, 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 diazomethane.

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

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