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 This information may be superseded by new developments in the field of industrial hygiene.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

INTRODUCTION

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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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

* Structure

(For Structure, see paper copy)

* Synonyms

1,4-Dichlorobenzene; parazene; dichlorocide, paramoth; santachlor;

PDCB; p-chlorophenyl chloride

* Identifiers

1. CAS No.: 106-46-7

2. RTECS No.: CZ4550000

3. DOT UN: 1592 58

4. DOT label: Keep away from food

* Appearance and odor

p-Dichlorobenzene is a colorless to white crystalline solid with a mothball-like odor. The air odor threshold concentration for p-dichlorobenzene is 0.18 part per million (ppm) parts of air.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 147

2. Boiling point (at 760 mm Hg): 174 degrees C (345 degrees F)

3. Specific gravity (water = 1): 1.25 at 55 degrees C (131 degrees F)

4. Vapor density: 5.1

5. Melting point: 53 degrees C (127 degrees F)

6. Vapor pressure at 55 degrees C (131 degrees F): 10 mm Hg

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

8. Evaporation rate: Not applicable.

* Reactivity

1. Conditions contributing to instability: Heat.

2. Incompatibilities: Contact between p-dichlorobenzene and strong oxidizers such as chlorine or permanganate should be avoided.

3. Hazardous decomposition products: Toxic gases and vapors such as hydrogen chloride, carbon dioxide and carbon monoxide may be released in a fire involving p-dichlorobenzene.

4. Special precautions: None reported.

* Flammability

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

1. Flash point: 55 degrees C (150 degrees F) (closed cup)

2. Autoignition temperature: Data not available.

3. Flammable limits in air (percent by volume): Lower, 1.7; upper, 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 o-dichlorobenzene.

Fires involving o-dichlorobenzene 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. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving o-dichlorobenzene [DOT 1993, Guide 58].

EXPOSURE LIMITS

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for p-dichlorobenzene is 75 ppm (450 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 p-dichlorobenzene of 1.7 ppm (limit of quantitation)() as a TWA for up to a 10-hour workday and a 40-hour workweek. NIOSH considers p-dichlorobenzene a potential occupational carcinogen [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned p-dichlorobenzene a threshold limit value (TLV) of 10 ppm (60 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek. The ACGIH lists p-dichlorobenzene as an animal carcinogen (A3 substance) [ACGIH 1994, p. 18].

* Rationale for Limits

The NIOSH limit is based on the risk of potential for cancer, eye and upper respiratory irritation, liver toxicity; kidney and liver cancer in animals [NIOSH 1992].

The ACGIH limit is based on the risk of eye irritation in humans, systemic toxicity noted in animals, and on recent studies suggesting potential carcinogenicity [ACGIH 1991, p. 413].

HEALTH HAZARD INFORMATION

* Routes of Exposure

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

* Summary of toxicology

1. Effects on Animals: p-Dichlorobenzene is an eye and upper respiratory tract irritant, a liver and kidney toxin, and a carcinogen [Hathaway et al. 1991]. The oral LD(50) in rats is 500 mg/kg [NIOSH 1995]. The dermal LD(50) in rabbits is greater than 2 gm/kg [NIOSH 1995]. Rats, guinea pigs, and rabbits exposed by inhalation to 798 ppm 5 days/week, 7 hours/day for as many as 69 exposures showed tremors, weakness, weight loss, eye irritation, and, at autopsy, cloudy swelling of the liver and centrilobular necrosis; in some animals, the kidneys also showed damage [Clayton and Clayton 1982]. At 158 ppm for as many as 219 days, some animals exhibited growth depression, an increase in liver weights, and histopathological changes to the liver [Clayton and Clayton 1982]. Oral administration of p-dichlorobenzene caused increases in kidney and liver weights and slight necrosis and cirrhosis of the liver [Clayton and Clayton 1982]. Male rats gavaged with p-dichlorobenzene at 150 or 300 mg/kg for 2 years had a significant dose-related increased incidence or tubular cell adenocarcinomas of the kidney, and animals of both sexes developed nephropathy. Both male and female mice dosed with 600 mg/kg p-dichlorobenzene for 2 years developed an increased incidence of hepatocellular adenomas and carcinomas and non-neoplastic lesions of the liver [Hathaway et al. 1991]. The National Toxicology Program concluded that there is clear evidence that p-dichlorobenzene is carcinogenic in male rats and in mice of both sexes [Hathaway et al. 1991]. In addition, the International Agency for Research on Cancer (IARC) has concluded that there is sufficient evidence that p- dichlorobenzene is carcinogenic in treated animals [IARC 1987].

2. Effects on Humans: p-Dichlorobenzene is an eye and upper respiratory tract irritant. Eye and nose irritation is painful at concentrations of 50 ppm and becomes severely painful at 160 ppm [Hathaway et al. 1991]. Contact of p-dichlorobenzene particles with the eye or the skin causes pain but does not produce damage; repeated exposure of the skin causes mild irritation [Hathaway et al. 1991]. One case of allergic purpura that is attributed to p-dichlorobenzene exposure has been reported [Hathaway et al. 1991]. Five individuals occupationally exposed by inhalation to a mixture of o- and p-dichlorobenzene or during household use experienced headaches, swelling of the area around the eyes, and runny nose. The four most heavily exposed individuals developed anorexia, weight loss, nausea, vomiting, and liver necrosis with jaundice [Hathaway et al. 1991]. Two of these individuals died, and a third developed cirrhosis; the extent to which these individuals may also have been exposed to other toxic substances is unknown. There are four case reports of severe blood disorders (dyscrasias) in humans exposed to unspecified concentrations of p-dichlorobenzene in solvents or products containing mixtures of chlorobenzenes [ACGIH 1991]. A worker exposed for 10 years to a solvent containing p-dichlorobenzene developed chronic lymphoid leukemia [ACGIH 1991]. IARC classified p-dichlorobenzene as a 2B substance, possibly carcinogenic to humans, carcinogen [IARC 1987].

* Signs and symptoms of exposure

1. Acute exposure: Exposure to p-dichlorobenzene may cause eye and upper respiratory tract irritation, headache, swelling around the eyes, runny nose, and nausea. Contact of the eye with particles of p-dichlorobenzene causes pain, and direct skin contact with this substance causes a burning sensation and slight skin irritation. If swallowed, it may cause a burning pain in the stomach, nausea, vomiting, and diarrhea. Methemoglobinemia may also result from exposure to p-dichlorobenzene [NLM 1995].

2. Chronic exposure: Repeated exposure to p-dichlorobenzene may induce anorexia, weight loss, and liver and kidney damage. Four cases of blood dyscrasias, including leukemia, have been attributed to exposure to p-dichlorobenzene, either alone or with other substances. A single case of allergic purpura thought to have been caused by exposure to p-dichlorobenzene has been reported.

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 p-dichlorobenzene and lead to worker exposures to this substance:

* The manufacture and transportation of p-dichlorobenzene

* Used as an insecticidal fumigant in agricultural applications and by consumers to mothproof clothes

* Used as a deodorant for garbage, restrooms, and odorous interior spaces

* Used to control mildew and mold in agricultural applications and on leathers and fabrics in stored containers

* Used as a chemical intermediate in the production of 2,5-dichloroaniline, dyes, pharmaceuticals, other chemicals, polyphenylene resins for the electrical and electronics industries, and insecticides

Methods that are effective in controlling worker exposures to p-dichlorobenzene, 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 p-dichlorobenzene 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 p-dichlorobenzene, 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 liver, kidneys, respiratory tract, blood, and skin. 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 p-dichlorobenzene 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 liver, kidneys, respiratory tract, blood, or skin.

* 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 p-dichlorobenzene exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of p-dichlorobenzene on the liver, kidneys, respiratory tract, blood, or skin. 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 p-dichlorobenzene 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. The primary metabolite of chlorobenzene in humans is 4-chlorocatechol in the urine. However, no biological monitoring test acceptable for routine use has yet been developed for p-dichlorobenzene.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne p-dichlorobenzene is made using a charcoal tube (100/50 mg sections, 20/40 mesh). Samples are collected at a maximum flow rate of 0.2 liter/minute (TWA or STEL) for a maximum collection volume of 3 liters (STEL) or 10 liters (TWA). The samples are treated with carbon disulfide. Analysis is conducted by gas chromatography using a flame ionization detector (GC/FID). This method is fully validated and is described in the OSHA Computerized Information System [OSHA 1994] and in NIOSH Method No. 1003 [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If p-dichlorobenzene contacts the skin, workers should wash three times; first with soap and water, then with alcohol, and finally with soap and water again.

Clothing contaminated with p-dichlorobenzene 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 p-dichlorobenzene, particularly its potential for causing irritation.

A worker who handles p-dichlorobenzene 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 p-dichlorobenzene or a solution containing p-dichlorobenzene is handled, processed, or stored.

STORAGE

p-Dichlorobenzene 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]. Outside storage is preferred; if stored inside, a standard flammable liquids storage room or cabinet should be used. Containers of p-dichlorobenzene should be protected from physical damage and ignition sources, and should be stored separately from strong oxidizers such as chlorine or permanganate.

SPILLS AND LEAKS

In the event of a spill or leak involving p-dichlorobenzene, 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 after the clean-up is complete.

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 p-dichlorobenzene 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

p-Dichlorobenzene 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 p-dichlorobenzene is 100 pounds. If an amount equal to or greater than this quantity is released within a 24-hour period in a manner that will expose persons outside the facility, employers are required to do the following:

- Notify the National Response Center immediately at (800) 424-8802 or at (202) 426-2675 in Washington, D.C. [40 CFR 302.6].

* Community right-to-know requirements Employers who own or operate facilities in SIC codes 20 to 39 that employ 10 or more workers and that manufacture 25,000 pounds or more of p-dichlorobenzene per calendar year or otherwise use 10,000 pounds or more of p-dichlorobenzene 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 p-dichlorobenzene 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. p-Dichlorobenzene is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. U072. It is approved for land disposal after treatment and only if the concentration of p-dichlorobenzene in the waste or treatment residual does not exceed 6.2 mg/kg.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of p-dichlorobenzene 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 p-dichlorobenzene. 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 p-dichlorobenzene. The resistance of various materials to permeation by p-dichlorobenzene is shown below:

(*) Not recommended, degradation may occur

To evaluate the use of these PPE materials with p-dichlorobenzene, 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 p-dichlorobenzene.

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.

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