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 This information may be superseded by new developments in the field of industrial hygiene.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

INTRODUCTION

This guideline summarizes pertinent information about dimethylaniline 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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(8)H(11)N

* Structure

(For Structure, see paper copy)

* Synonyms

N,N-Dimethylaniline, DMA, aminodimethylbenzene, (dimethylamino)-benzene, n,n-dimethylbenzeneamine, dimethylphenylamine

* Identifiers

1. CAS No.: 121-69-7

2. RTECS No.: BX4725000

3. DOT UN: 2253 57

4. DOT label: Poison

* Appearance and odor

Dimethylaniline is an oily, yellow- to brown-colored liquid with a characteristic amine-like odor. The air odor threshold concentration for dimethylaniline is 0.013 part per million (ppm) parts of air.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 121.2

2. Boiling point (at 760 mm Hg): 192.8 degrees C (379 degrees F)

3. Specific gravity (water = 1): 0.96 at 20 degrees C (68 degrees F)

4. Vapor density: 4.2

5. Freezing point: 2.5 degrees C (36.5 degrees F) (Solidifies)

6. Vapor pressure at 20 degrees C (68 degrees F): Less than 1 mm Hg

7. Solubility: Insoluble in water; soluble in alcohol, ether, acetone, benzene, and chloroform.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Heat or flame.

2. Incompatibilities: Contact between dimethylaniline and strong oxidizers, such as benzoyl peroxide or diisopropyl peroxidicarbonate, or strong acids should be avoided.

3. Hazardous decomposition products: Toxic gases and vapors (such as aniline, the oxides of nitrogen, and carbon monoxide) may be released in a fire involving dimethylaniline.

4. Special precautions: None reported.

* Flammability

The National Fire Protection Association has assigned a flammability rating of 2 (moderate fire hazard) to dimethylaniline.

1. Flash point: 62.8 degrees C (145 degrees F) (closed cup)

2. Autoignition temperature: 371 degrees C (700 degrees F)

3. Flammable limits in air: Data not available.

4. Extinguishant: For small fires use dry chemical, carbon dioxide, water spray, or regular foam. Use water spray or regular foam to fight large fires involving dimethylaniline.

Fires involving dimethylaniline should be fought upwind from the maximum distance possible. 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. Vapors are an explosion and poison hazard indoors, outdoors, or in sewers. Containers of dimethylaniline 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 using an unmanned device until well after the fire is out. Stay away from the ends of containers. Dike fire control water for later disposal; do not scatter this material. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving dimethylaniline.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for dimethylaniline is 5 ppm (25 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration. The OSHA PEL also bears a "Skin" notation, which indicates that the cutaneous route of exposure (including mucous membranes and eyes) contributes to overall exposure [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 dimethylaniline of 5 ppm (25 mg/m(3)) as a TWA for up to a 10-hour workday and a 40-hour workweek and a short-term exposure limit (STEL) of 10 ppm (50 mg/m(3)). NIOSH also assigns a "Skin" notation to dimethylaniline [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned dimethylaniline a threshold limit value (TLV) of 5 ppm (25 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek and a short-term exposure limit (STEL) of 10 ppm (50 mg/m(3)) for periods not to exceed 15 minutes. Exposures at the STEL concentration should not be repeated more than four times a day and should be separated by intervals of at least 60 minutes. The ACGIH also assigns a "Skin" notation to dimethylaniline [ACGIH 1994, p. 19].

* Rationale for Limits

The NIOSH limits are based on the risk of anoxia resulting from the formation of methemoglobin [NIOSH 1992].

The ACGIH limits are based on the risk of neurotoxic effects and anoxia [ACGIH 1991, p. 484].

HEALTH HAZARD INFORMATION

* Routes of Exposure

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

* Summary of toxicology

1. Effects on Animals: The absorption of dimethylaniline, either by inhalation of the vapor or by absorption of the liquid through the skin, causes hypoxia or anoxia due to the formation of methemoglobin in the blood. Dimethylaniline also causes central nervous system depression. Dogs administered a single 50 mg/kg dose of dimethylaniline orally developed methemoglobinemia. The 4-hour LC(50) in rats is 250 mg/m(3), and the dermal LD(50) for rabbits is 1.77 mg/kg [Hathaway et al. 1991; Sax and Lewis 1989; NIOSH 1995]. The repeated inhalation exposure of rats to dimethylaniline for 100 days at 0.3 mg/m(3) caused anemia, methemoglobinemia, leukopenia, and impairment of adrenal gland and liver functions [NIOSH 1995; ACGIH 1991]. In dogs, the repeated subcutaneous administration of 1.5 g produced vomiting, weakness, cyanosis, methemoglobinemia, and elevation of the level of gamma proteins in the blood [Hathaway et al. 1991]. Dimethylaniline is readily absorbed through the skin in toxic amounts. Direct contact of dimethylaniline with the skin of rabbits caused slight irritation. Severe burns resulted when 0.005 ml was instilled into the eyes of rabbits [Hathaway et al. 1991]. The National Toxicology Program (NTP) conducted a two year study with groups of 50 male and 50 female rats and mice at doses of 0, 3, or 30 mg/kg (rats) and 0, 15, or 30 mg/kg (mice). The dimethylaniline was administered 5 days a week for 103 weeks. The study found some evidence of carcinogenic activity for high-dose male rats, as indicated by the increased incidences of sarcomas or osteosarcomas of the spleen [ACGIH 1991].

2. Effects on Humans: Dimethylaniline is readily absorbed through the skin, lungs, and gastrointestinal tract and rapidly produces methemoglobinemia and central nervous system depression. Following a severe acute exposure, two workers collapsed immediately, were unconscious for 8 hours, and complained of visual disturbances and intense abdominal pain after regaining consciousness [ACGIH 1991]. Dimethylaniline is reported to be a more severe central nervous depressant than aniline [Gosselin 1984].

* Signs and symptoms of exposure

1. Acute exposure: The acute effects of exposure to dimethylaniline by inhalation, skin absorption, or ingestion are severe headache, visual disturbances, nausea, cyanosis, labored breathing, drowsiness, irregular pulse, paralysis, convulsions, unconsciousness, staggering walk, lethargy, ringing in the ears, dizziness, and intense abdominal pain [ACGIH 1991; Gosselin 1984; Hathaway et al. 1991; Genium 1989].

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

* The manufacture and transportation of dimethylaniline

* Used in synthesis of dye and dye intermediates, explosives, pharmaceuticals, rubber chemicals, polyester resin systems, intermediates for vanillin, and Michler's ketone

* Used in absorption of sulfur dioxide and as a solvent

* Used as a stabilizer and an analytical reagent for methanol, methyl furfural, hydrogen peroxide, nitrate, alcohol, and formaldehyde

* Used as a catalytic hardener in certain fiberglass resins and as a rubber vulcanizer

Methods that are effective in controlling worker exposures to dimethylaniline, 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 dimethylaniline 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 dimethylaniline, 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 blood, kidneys, liver, and cardiovascular 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 dimethylaniline 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 blood, kidneys, liver, or cardiovascular 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 dimethylaniline exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of dimethylaniline on the blood, kidneys, liver, or cardiovascular 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. Because occupational exposure to dimethylaniline may cause diseases with prolonged latent periods, the need for medical surveillance may extend well beyond the termination of employment.

* Biological monitoring

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. During or end of shift blood samples can be used to determine a worker's exposure to dimethylaniline by analyzing for methemoglobin in the blood. A biological exposure index of 1.5 percent hemoglobin has been published for those chemicals that induce methemoglobin.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne dimethylaniline is made using a coated XAD-7 tube (80/40 mg sections); coating is 10 percent phosphoric 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 0.2N NH(4)OH in methanol. Analysis is conducted by gas chromatography using a flame ionization detector (GC/FID). This method is not yet validated and is described in the OSHA Computerized Information System [OSHA 1994]. NIOSH has also published a method (Method No. 2002-aromatic amines) for the determination of a worker's exposure to dimethylaniline that requires sample collection on a silica gel tube. Analysis for this method is also conducted by gas chromatography using a flame ionization detector (GC/FID) [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If dimethylaniline contacts the skin, workers should immediately wash the affected areas twice with soap and water, followed by showering from head to foot. Special attention should be given to washing the hair and scalp, finger- and toenails, nostrils, and ear canals.

Clothing contaminated with dimethylaniline 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 dimethylaniline, particularly its potential to be absorbed by the skin and to cause difficulty in breathing.

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

STORAGE

Dimethylaniline 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 dimethylaniline should be protected from physical damage, ignition sources, and sunlight, and should be stored separately from strong oxidizers, such as benzoyl peroxide or diisopropyl peroxidicarbonate, and strong acids. Empty containers of dimethylaniline should be handled appropriately.

SPILLS AND LEAKS

In the event of a spill or leak involving dimethylaniline, 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. 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 reduce vapors, but the spray may not prevent ignition in closed spaces.

7. For small liquid spills, cover and mix with a 9:1 mixture of sand and soda ash and deposit in sealed containers.

8. For large liquid spills, build dikes far ahead of the spill to contain the dimethylaniline for later reclamation or disposal.

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

Dimethylaniline 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 dimethylaniline 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 dimethylaniline per calendar year or otherwise use 10,000 pounds or more of dimethylaniline 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 dimethylaniline 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 dimethylaniline 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 dimethylaniline 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 dimethylaniline. 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 dimethylaniline. The resistance of one PPE material to permeation by dimethylaniline is shown below:

To evaluate the use of this or other PPE materials with dimethylaniline, 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 dimethylaniline.

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.

Amoore JE, Hautala E [1983]. 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.

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