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 This information may be superseded by new developments in the field of industrial hygiene.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

INTRODUCTION

This guideline summarizes pertinent information about methacrylic acid 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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(4)H(6)O(2)

* Structure

(For Structure, see paper copy)

* Synonyms

2-Methylpropenoic acid; þ-methylacryclic acid; 2-methylacrylic acid;

methacrylic acid, inhibited (DOT) * Identifiers

1. CAS No.: 79-41-4

2. RTECS No.: OZ2975000

3. DOT UN: 2531 60 (methacrylic acid, inhibited)

4. DOT label: Corrosive (methacrylic acid, inhibited)

* Appearance and odor

Methacrylic acid is a colorless liquid with an acrid, repulsive odor. The commercial product usually contains an inhibitor to prevent polymerization.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 86.09

2. Boiling point (at 760 mm Hg): 163 degrees C (325.4 degrees F)

3. Specific gravity (water = 1): 1.01 at 20 degrees C (68 degrees F)

4. Vapor density: Data not available.

5. Melting point: 16 degrees C (60.8 degrees F)

6. Vapor pressure at 25.5 degrees C (78 degrees F): 1 mm Hg

7. Solubulity: Soluble in warm water, alcohol, ether, alcohol and most organic solvents.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Methacrylic acid can polymerize upon exposure to traces of hydrochloric acid or heat. Exposure to light and air should also be avoided to prevent possible polymerization.

2. Incompatibilities: Contact between methacrylic acid and oxidizing agents such as peroxides, amines, strong bases, elevated temperatures, or hydrochloric acid (HCL) may cause reactions to occur.

3. Hazardous decomposition products: Toxic gases (such as carbon monoxide) may be released in a fire involving methacrylic acid.

4. Special precautions: Exothermic polymerization may occur spontaneously. If polymerization takes place inside tightly sealed containers, violent rupture of container may result. Exposure to light or air may also cause polymerization.

* Flammability

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

1. Flash point: 77 degrees C (171 degrees F) (open cup)

2. Autoignition temperature: Data not available.

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, fog, or regular foam to fight large fires involving methacrylic acid.

Fires involving methacrylic acid 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. Containers of methacrylic acid 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 methacrylic acid.

EXPOSURE LIMITS

* OSHA PEL

The Occupational Safety and Health Administration (OSHA) does not currently regulate methacrylic acid.

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for methacrylic acid of 20 parts per million (ppm) parts of air (70 mg/m(3)) as a TWA for up to a 10-hour workday and a 40-hour workweek. NIOSH also assigns a "Skin" notation, which indicates that the cutaneous route of exposure, including mucous membranes and eyes, contributes to overall exposure] [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned methacrylic acid a threshold limit value (TLV) of 20 ppm (70 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 25].

* Rationale for Limits

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

The ACGIH limit is based on the risk of eye and skin irritation by analogy to acrylic acid [ACGIH 1991, p. 899].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to methacrylic acid can occur through inhalation, ingestion, eye or skin contact, and absorption through the skin [ACGIH 1991].

* Summary of toxicology

1. Effects on Animals: Methacrylic acid is a corrosive irritant and may affect the eyes, skin, kidneys, liver, and lungs in exposed animals [ACGIH 1991]. The dermal LD(50) in rabbits is 500 mg/kg [NIOSH 1991]. Direct contact with the eyes or skin can result in corrosion [Hathaway et al. 1991; ACGIH 1991]. The oral LD(33) and LD(50) in rats is 60 and 2,260 mg/kg, respectively [NIOSH 1991; ACGIH 1991]. The LC(50) in rats is approximately 1,900 ppm for 4 hours [NLM 1992]. Rats exposed to 300 ppm methacrylic acid for 6 hours/day for 20 days developed kidney congestion [ACGIH 1991]. Rats exposed to 1,300 ppm 5 hours/day for 5 days showed signs of nose and eye irritation, but no adverse effects on hematologic or urinary effects were observed [Hathaway et al. 1991; ACGIH 1991]. Oral administration of 10 or 5 mg/kg/day for 5 days in rats resulted in slight alveolar hemorrhage and moderate granularity of liver cytoplasm; this effect was attributed to the corrosive action of methacrylic acid [ACGIH 1991].

2. Effects on Humans: Methacrylic acid can affect the eyes, skin, and immune system in humans [ACGIH 1991]. Exposure to methacrylic acid vapor may produce skin and eye irritation [Patnaik 1992]. In a case study involving 37 acrylic acid resin workers, methacrylic acid caused sensitization in a few of the workers and thus appears to be a sensitizing agent [ACGIH 1991]. Skin toxicity and a severe corneal burn were observed in a population of workers exposed to up to 113 ppm methacrylic acid [ACGIH 1991].

* Signs and symptoms of exposure

1. Acute exposure: The signs and symptoms of acute exposure to methacrylic acid include irritation of the eyes and skin, corneal burns, and possible blindness [ACGIH 1991].

2. Chronic exposure: The signs and symptoms of chronic exposure to methacrylic acid include skin irritation and rash, and sensitization [Clayton and Clayton 1982; ACGIH 1991].

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 methacrylic acid and lead to worker exposures to this substance:

* The manufacture and transportation of methacrylic acid

* Use as a monomer in the manufacture of methacrylate resins and polymers

* Use in organic synthesis

Methods that are effective in controlling worker exposures to methacrylic acid, 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 methacrylic acid 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 methacrylic acid, 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 system. 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 methacrylic acid 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 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 methacrylic acid exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of methacrylic acid on the eyes, skin, or respiratory 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 methacrylic acid.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne methacrylic acid is made using two XAD-8 tubes in series. Samples are collected at a maximum flow rate of 0.2 liter/minute (TWA) until a maximum collection volume of 20 liters is reached. The sample is then treated with methanol. Analysis is conducted by high performance liquid chromatography with an ultraviolet detector (HPLC/UV). This method is described in the OSHA Computerized Information System [OSHA 1994].

PERSONAL HYGIENE PROCEDURES

If methacrylic acid contacts the skin, workers should flush the affected areas immediately with plenty of water, followed by washing with soap and water. For reddened or blistered skin, consult a physician.

Clothing contaminated with methacrylic acid 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 methacrylic acid, particularly its potential for causing skin irritation.

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

STORAGE

Methacrylic acid 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 methacrylic acid should be protected from physical damage, exposure to light and air and should be stored separately from oxidizing agents such as peroxides, hydrochloric acid, amines, and strong bases.

SPILLS AND LEAKS

In the event of a spill or leak involving methacrylic acid, 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. Do not touch the spilled material; stop the leak if it is possible to do so without risk.

2. Notify safety personnel.

3. Remove all sources of heat and ignition.

4. Ventilate the area of the spill or leak.

5. For small dry spills, use a clean shovel and place the material into a clean, dry container; cover and remove the container from the spill area.

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

7. For large liquid spills, build dikes far ahead of the spill to contain the methacrylic acid 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

Methacrylic acid 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 methacrylic acid; 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 methacrylic acid 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 methacrylic acid 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 methacrylic acid 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 methacrylic acid. 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 methacrylic acid. The resistance of various materials to permeation by methacrylic acid is shown below:

(*) Not recommended, degradation may occur

To evaluate the use of these materials with methacrylic acid, 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 methacrylic acid.

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.

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ATS [1987]. Standardization of spirometry -- 1987 update. American Thoracic Society. Am Rev Respir Dis 136:1285-1296.

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