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This guideline summarizes pertinent information about xylene 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine periodically whether new information is available.
SUBSTANCE IDENTIFICATION * Formula C(6)H(4)(CH(3))(2)* Structure (For Structure, see paper copy)* Synonyms Dimethyl benzene; xylol; methyl toluene; 1,4-dimethyl-benzene; Violet 3* Identifiers 1. CAS 1330-20-7* Appearance and odor The xylene in commercial use is composed of a mixture of the three isomers ortho-xylene, meta-xylene, and para-xylene; the meta isomer predominates in these mixtures. o-Xylene and m-xylene are clear, colorless, flammable liquids that have characteristically sweet, balsam-like odors. At low temperatures, the para-isomer occurs in the form of clear, colorless plates.CHEMICAL AND PHYSICAL PROPERTIES * Physical data 1. Molecular weight: 106* Reactivity 1. Conditions contributing to instability: Heat, sparks, or open flame.* Flammability The National Fire Protection Association has assigned a flammability rating of 3 (severe fire hazard) to xylene.1. Flash point: 27 to 32 degrees C (81 to 90 degrees F). 2. Autoignition temperature: 464 degrees C (867 degrees F). 3. Flammable limits in air (percent by volume): Lower, 1; upper, 7. 4. Extinguishant: Use foam, dry chemical, or carbon dioxide to fight fires involving xylene. Water may be used to reduce the rate of burning or to cool fire-exposed containers. Fires involving xylene should be fought upwind and from the maximum distance possible. Keep unnecessary people away; isolate hazard area and deny entry. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Vapor explosion and poison hazards may occur indoors, outdoors, or in sewers. Vapors may travel to a source of ignition and flash back. Containers of xylene 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 containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Personnel should withdraw immediately if a rising sound from a venting safety device is heard or if there is discolora-tion of a container due to fire. Dikes should be used to contain fire-control water for later disposal. If a tank car or truck is involved in a fire, personnel should isolate an area of a half a mile in all directions. Firefighters should wear a full set of protective clothing, including a self-contained breathing apparatus, when fighting fires involving xylene. Firefighters' protective clothing may provide limited protection against fires involving xylene. * Warning properties The odor threshold for xylene is 1 part per million (ppm) parts of air. Because this value is below the Occupational Safety and Health Administration (OSHA) current permissible exposure limit (PEL) of 100 ppm [29 CFR 1910.1000, Table Z-1-A], xylene is considered to have adequate warning properties.* Eye irritation properties The eye irritation threshold for xylene is 200 ppm (870 mg/m(3)).EXPOSURE LIMITS The current OSHA PEL for xylene is 100 ppm (435 milligrams per cubic meter (mg/m(3)) of air) as an 8-hour time-weighted average (TWA) concentration. The National Institute for Occupational Safety and Health (NIOSH) recommended exposure limits (RELs) for xylene are 100 ppm (435 mg/m(3)) as a TWA for up to a 10-hour workshift and a 40-hour workweek and 200 ppm (868 mg/m(3)) for 10 minutes as a short-term limit [NIOSH Recommendations, 1988]. The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned xylene a threshold limit value (TLV) of 100 ppm (435 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 150 ppm (655 mg/m(3)) for periods not to exceed 15 minutes [ACGIH 1988, p. 42]. The OSHA and ACGIH limits are based on the risk of irritant, narcotic, and chronic effects associated with exposure to xylene, and the NIOSH limit is based on xylene's potential to cause central nervous system depression and respiratory irritation.
HEALTH HAZARD INFORMATION * Routes of Exposure Exposure to xylene can occur via inhalation, ingestion, eye or skin contact, and, to a small extent, by absorption through the skin.* Summary of toxicology 1. Effects on Animals: Xylene exposure produces central nervous system depression and irritation of the eyes and skin in animals. Xylene is also fetotoxic and teratogenic in several species of experimental animals when administered by the oral or inhalation routes [RTECS 1989]. The LC(50) in the rat for a 4-hour xylene inhalation exposure is 5000 ppm, and the oral LD(50) in the same species is 4300 mg/kg [RTECS 1989]. The meta isomer may be more acutely toxic than the o- or p-isomer: mice exposed for 24 hours to 2010 ppm of the m-isomer or to 3062 ppm of the o-isomer died, while exposure for the same period to 4912 ppm of the p-isomer did not cause death [Proctor, Hughes, and Fischman 1988, p. 511]. Rats exposed to a 1600-ppm concentration of xylene (isomer unspecified) for 2 or 4 days showed signs of irritation, became uncoor-dinated, lost weight, had an increased red blood cell count, exhibited signs of narcosis, and died [Proctor, Hughes, and Fischman 1988, p. 511]. Rats exposed to a 980-ppm concentration of xylene for 7 days developed leukopenia, and autopsy revealed kidney congestion and hyperplasia of the bone marrow and spleen [Proctor, Hughes, and Fischman 1988, p. 511]. In contact with the eye, xylene causes irritation of the conjunctiva, tur-bidity of the cornea, swelling, and tearing in rabbits [Clayton and Clayton 1981, p. 3292]. Repeated application to rabbit skin of a 95- or 100-percent solution of xylene causes redness, moderate irritation, and slight necrosis [Proctor, Hughes, and Fischman 1988, p. 511; RTECS 1989]. Rabbits exposed for 40 to 55 days to a xylene concentra-tion of 1150 ppm developed a decrease in their red and white blood cell counts and an increase in thrombocytes, but these effects were reversible [Proctor, Hughes, and Fischman 1988, p. 571]. In chronic inhalation studies, rats and dogs exposed to 800 ppm for 6 hours/day for 65 days showed no measurable ill effects [ACGIH 1986, p. 637]. No signs of carcinogenicity were noted in long-term gavage studies in rats and mice [Proctor, Hughes, and Fischman 1988, p. 511]. Administered subcutaneously to rats at 300 mg/kg/day for 6 weeks or at 700 mg/kg/day for 9 weeks, xylene failed to cause hematopoietic effects; earlier reports of xylene's myelotoxicity appear to have been based on exposures to xylene contaminated with benzene, a known myelotoxin [HSDB 1986; ACGIH 1986, p. 637]. The offspring of pregnant rats inhaling 50 mg/m(3) xylene for 6 hours on days 1 to 21 of pregnancy or 250 or 600 mg/m(3) for 24 hours on days 7 to 15 of pregnancy had an increased incidence of musculoskeletal abnormalities, and the offspring of pregnant mice administered xylene by inhalation or oral dosing also showed developmental abnormalities [RTECS 1989].* Signs and symptoms of exposure 1. Acute exposure: The signs and symptoms of acute exposure to xylene include headache, fatigue, irritability, lassitude, nausea, anorexia, flatulence, irritation of the eyes, nose, and throat, and motor incoordination and impairment of equilibrium. Flushing, redness of the face, a sensation of increased body heat, increased salivation, tremors, dizziness, confusion, and cardiac irritability have also been reported.* Emergency procedures: In the event of an emergency, remove the victim from further exposure, send for medical assistance, and initiate the following emergency procedures:EXPOSURE SOURCES AND CONTROL METHODS The following operations may involve xylene and lead to worker exposures to this substance:
1. ACGIH [1986]. Industrial ventilation--a manual of recommended practice. 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 MONITORING * 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, placement of workers in jobs that do not jeopardize their safety or health, 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., indus-trial hygiene monitoring, engineering controls, and personal protective equipment). A medical monitoring program is intended to supplement, not replace, such measures. To place workers effectively and to detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the period 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 xylene, the examining physician 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 central nervous system, blood, liver, kidneys, and skin.* Periodic medical examinations and biological monitoring 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 xylene exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of xylene on the central nervous system, blood, liver, kidneys, 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.* Medical examinations recommended at the time of job transfer or termination 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 xylene may cause diseases with prolonged latent periods, the need for medical monitoring may extend well beyond the termination of employment.WORKPLACE MONITORING AND MEASUREMENT PROCEDURES Determination of a worker's exposure to airborne xylene 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 per minute until a maximum air volume of 12 liters is collected. The sample is then treated with carbon disulfide to extract the xylene. Analysis is conducted by gas chromatography using a flame ionization detector. This method has a sampling and analytical error of 0.10 and is included as NIOSH Method 1501 in the NIOSH Manual of Analytical Methods, 3rd edition, Volume 2 [NIOSH 1984].
PERSONAL HYGIENE PROCEDURES If xylene contacts the skin, workers should immediately wash the affected areas with soap and water. Clothing contaminated with xylene 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 xylene, particularly its potential to cause dryness and irritation of the skin. A worker who handles xylene should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, or using toilet facilities. Workers should not eat, drink, or use tobacco products in areas where xylene is handled, processed, or stored. STORAGE Xylene 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 or detached storage is preferred; inside storage must be in a standard flammable liquids storage room or cabinet. The ventilation used in storage areas must be of explosion-proof design. Containers of xylene should be protected from physical damage and should be stored separately from strong oxidizers, heat, sparks, and open flame. Only nonsparking tools may be used to handle xylene. To prevent static sparks, containers must be grounded and bonded for transfers. Because empty containers that formerly contained xylene may still hold product residues, they should be handled appropriately. SPILLS AND LEAKS In the event of a spill or leak involving xylene, 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 potentially explosive atmospheres using maximally explosion-proof equipment. 5. Use nonsparking tools for cleanup. 6. Water spray may be used to reduce vapors, but the spray may not prevent ignition in closed spaces. 7. For small liquid spills, take up with sand or other noncombustible absorbent material and place into closed containers for later disposal. 8. For large liquid spills, build dikes far ahead of the spill to contain the xylene for later reclamation or disposal. EMERGENCY PLANNING, COMMUNITY RIGHT-TO-KNOW, AND HAZARDOUS WASTE MANAGEMENT REQUIREMENTS The Environmental Protection Agency's (EPA's) regulatory requirements for emergency planning, community right-to-know, and hazardous waste management may vary over time. Users are therefore advised to determine periodically whether new information is available. * Emergency planning requirements Xylene is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (Title III).* Reportable quantity requirements (releases of hazardous substances) A hazardous substance release is defined by EPA as any spilling, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to notify the proper Federal authorities.* Community right-to-know requirements Employers who own or operate facilities in SIC codes 20-39 that employ 10 or more employees and that manufacture 25,000 pounds or more of xylene per calendar year or otherwise use 10,000 pounds or more of xylene per calendar year are required by EPA (49 CFR Part 372.30) to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of xylene 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), EPA has specifically listed many chemical wastes as hazardous. Xylene is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. U239. It is approved for land disposal as long as the concentration of xylene in the waste or treatment residual does not exceed 28 mg/kg. Xylene also may be disposed of in an organometallic or organic lab pack that meets the requirements of 40 CFR 264.316 or 265.316.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 xylene 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 emergency situations. If the use of respirators is necessary, the only respirators permitted are those 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 (see Table 1), an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, 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 NIOSH Respirator Decision Logic [NIOSH 1987c] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].PERSONAL PROTECTIVE EQUIPMENT Protective clothing should be worn to prevent skin contact with xylene. Impervious gloves, boots, aprons, gauntlets, and other protective clothing are recommended for use as necessary [Genium MSDS 1988, No. 318]. Chemical protective clothing should be selected on the basis of available performance data, manufacturers' recommendations, and evaluation of the clothing under actual conditions of use. The following materials have been recommended for use against permeation by xylene and may provide protection for periods greater than 8 hours: polyvinyl alcohol and Viton. Materials that may withstand permeation for more than 4 but fewer than 8 hours are Teflon and polyethylene/ethylene vinyl alcohol [Forsberg and Mansdorf 1989, p. 46]. Natural rubber, butyl rubber, neoprene, a nitrile rubber and polyvinyl chloride mixture, nitrile rubber, polyethylene, polyvinyl chloride, and a neoprene and natural rubber mixture have demonstrated poor resistance to permeation by xylene [Schwope et al. 1987, p. 99; Forsberg and Mansdorf 1989, p. 46]. If xylene is dissolved in an organic solvent, the permeation properties of both the solvent and the mixture must be considered when selecting personal protective equipment and clothing. Safety glasses, goggles, or faceshields should be worn during operations in which xylene might contact the eyes (e.g., through splashes of solution). Eyewash fountains and emergency showers should be available within the immediate work area whenever the potential exists for eye or skin contact with xylene. Contact lenses should not be worn if the potential exists for xylene exposure [NIOSH/OSHA Occupational Health Guideline 1981, p. 3; Genium MSDS 1988, No. 318].
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