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 This information may be superseded by new developments in the field of industrial hygiene.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 4-METHOXYPHENOL

INTRODUCTION

This guideline summarizes pertinent information about 4-methoxyphenol 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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(7)H(8)O(2)

* Structure

(For Structure, see paper copy)

* Synonyms

Hydroquinone monomethyl ether, p-hydroxyanisole, mequinol y

* Identifiers

1. CAS No.: 150-76-5

2. RTECS No.: SL7700000

3. Specific DOT number: None.

4. Specific DOT label: None.

* Appearance and odor

4-Methoxyphenol is a white to tan, waxy, flaky crystalline solid with an odor of caramel and phenol.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 124.15

2. Boiling point (at 760 mm Hg): 243 degrees C (469 degrees F)

3. Specific gravity (water = 1): 1.55 at 20 degrees C (68 degrees F)

4. Vapor density: Data not available.

5. Melting point: 57 degrees C (135 degrees F)

6. Vapor pressure: Data not available.

7. Solubility: Slightly soluble in water; soluble in organic solvents such as alcohol, ether and benzene.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Contact between 4-methoxyphenol and oxidizing agents, strong bases, acid chlorides, or acid anhydrides may cause reactions to occur.

3. Hazardous decomposition products: Toxic gases (such as carbon monoxide) may be released in a fire involving 4-methoxyphenol.

4. Special precautions: None reported.

* Flammability

The National Fire Protection Association has assigned a flammability rating of 1 (slight fire hazard) to 4-methoxyphenol.

1. Flash point: 132 degrees C (270 degrees F) (open cup)

2. Autoignition temperature: 421 degrees C (790 degrees F)

3. Flammable limits in air: None reported.

4. Extinguishant: Use dry chemical, carbon dioxide, alcohol-resistant foam, or water spray to fight fires involving 4-methoxyphenol. Water or foam may cause frothing.

Fires involving 4-methoxyphenol should be fought upwind from the maximum distance possible. Isolate the hazard area and deny access to unnecessary personnel. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving 4-methoxyphenol.

EXPOSURE LIMITS

* OSHA PEL

The Occupational Safety and Health Administration (OSHA) does not currently regulate 4-methoxyphenol.

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for 4-methoxyphenol of 5 milligrams per cubic meter (mg/m(3)) of air 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 4-methoxyphenol a threshold limit value (TLV) of 5 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 irritation, corneal damage, and central nervous system depression [NIOSH 1992].

The ACGIH limit is based on the risk of eye and skin toxicity and by analogy to hydroquinone [ACGIH 1991, p. 925].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to 4-methoxyphenol can occur through inhalation, ingestion, and eye or skin contact.

* Summary of toxicology

1. Effects on Animals: Exposure to 4-methoxyphenol can affect the eyes, skin, and central nervous systems [ACGIH 1991]. 4-Methoxyphenol caused moderate corneal damage when applied directly to the eye of rabbits [ACGIH 1991]. Dermal contact with 4-methoxyphenol for more than one day caused necrosis in rabbits [Clayton and Clayton 1981]. Guinea pigs treated with 20 percent concentration of 4-methoxyphenol in lanolin had skin depigmentation [ACGIH 1991]. The oral LD(50) in rats is 1,600 mg/kg [ACGIH 1991]. The gross signs of intraperitoneal poisoning were paralysis and anoxia at lower levels and narcosis at high levels [Clayton and Clayton 1981]. 4-Methoxyphenol was not a skin sensitizer in guinea pigs [Clayton and Clayton 1981].

2. Effects on Humans: Exposure to 4-methoxyphenol may produce burns to the skin and eyes [ACGIH 1991]. Two of eight workers handling 4-methoxyphenol developed skin depigmentation [ACGIH 1991].

* Signs and symptoms of exposure

1. Acute exposure: No signs or symptoms of acute exposure to 4-methoxyphenol have been reported in humans.

2. Chronic exposure: The sign and symptoms of chronic exposure to 4-methoxyphenol include skin discoloration.

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 4-methoxyphenol and lead to worker exposures to this substance:

* The manufacture and transportation of 4-methoxyphenol

* Use as a non-discoloring antioxidant for fats, oils, vitamins, and cosmetics

* Use as an inhibitor for acrylic monomers, acrylonitriles, and various polymers

* Use as a stabilizer for chlorinated hydrocarbons and ethyl cellulose

* Use in the manufacture of plasticizers, dyes, pharmaceuticals, and other chemicals

* Use as an ultraviolet inhibitor

Methods that are effective in controlling worker exposures to 4-methoxyphenol, 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 4-methoxyphenol 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 4-methoxyphenol, 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, respiratory system, and central nervous 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 4-methoxyphenol 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, respiratory system, 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 4-methoxyphenol exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of 4-methoxyphenol on the eyes, skin, respiratory system, 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 4-methoxyphenol.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne 4-methoxyphenol is made using a XAD-7 tube (100/50 mg sections, 15/50 mesh). 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 gas chromatography with a flame ionization detector (GC/FID). This method is described in the OSHA Computerized Information System [OSHA 1994].

PERSONAL HYGIENE PROCEDURES

If 4-methoxyphenol contacts the skin, workers should flush the affected areas immediately with plenty of water, followed by washing with soap and water.

Clothing contaminated with 4-methoxyphenol 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 4-methoxyphenol, particularly its potential for causing skin and eye irritation.

A worker who handles 4-methoxyphenol 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 4-methoxyphenol is handled, processed, or stored.

STORAGE

4-Methoxyphenol 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 4-methoxyphenol should be protected from physical damage and should be stored separately from oxidizing agents, strong bases, acid chlorides, and acid anhydrides.

SPILLS AND LEAKS

In the event of a spill or leak involving 4-methoxyphenol, 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. Use non-sparking tools.

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

4-Methoxyphenol 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 4-methoxyphenol; 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 4-methoxyphenol 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 4-methoxyphenol 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 4-methoxyphenol 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 4-methoxyphenol. 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 4-methoxyphenol. There are no published reports on the resistance of various materials to permeation by 4-methoxyphenol.

To evaluate the use of PPE materials with 4-methoxyphenol, 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 4-methoxyphenol.

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.

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

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Clayton G, Clayton F [1981-1982]. Patty's industrial hygiene and toxicology. 3rd rev. ed. New York, NY: John Wiley & Sons.

Genium [1990]. Material safety data sheet No. 455. Schenectady, NY: Genium Publishing Corporation.

Lewis RJ, ed. [1993]. Hawley's condensed chemical dictionary. 12th ed. New York, NY: Van Nostrand Reinhold Company.

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Mickelsen RL, Hall RC [1987]. A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.

Mickelsen RL, Hall RC, Chern RT, Myers JR [1991]. Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.

NFPA [1986]. Fire protection guide on hazardous materials. 9th ed. Quincy, MA: National Fire Protection Association.

NIOSH [1987a]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-116.

NIOSH [1987b]. NIOSH respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-108.

NIOSH [1989]. Registry of toxic effects of chemical substances: 4-Methoxyphenol. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

NIOSH [1992]. Recommendations for occupational safety and health: Compendium of policy documents and statements. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 92-100.

NIOSH [1994]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-116.

NJDH [1986]. Hazardous substance fact sheet: 4-Methoxyphenol. Trenton, NJ: New Jersey Department of Health.

NLM [1992]. Hazardous substances data bank: 4-Methoxyphenol. Bethesda, MD: National Library of Medicine.

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

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

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