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This guideline summarizes pertinent information about Methylene Bis (4-cyclohexylisocyanate) 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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(15)H(22)N(2)O(2) * Structure (For Structure, see paper copy) * Synonyms Bis (4-isocyanatocyclohexyl) methane; methylenedi-4,1-cyclohexylene ester isocyanic acid; nacconate H 12; dicyclohexylmethane-4,4'-diisocyanate; hydrogenated MDI; * Identifiers
Methylene bis(4-cyclohexylisocyanate) is a clear, colorless to light-yellow liquid. CHEMICAL AND PHYSICAL PROPERTIES * Physical data
The National Fire Protection Association has not assigned a flammability rating to methylene bis(4-cyclo-hexylisocyanate). Other sources rate methylene bis(4-cyclohexylisocyanate) as combustible when this substance is exposed to heat or open flame.
EXPOSURE LIMITS * OSHA PEL The Occupational Safety and Health Administration (OSHA) does not currently regulate methylene bis(4-cyclo-hexylisocyanate). * NIOSH REL The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) of 0.01 part per million (ppm) parts of air (0.11 milligram per cubic meter (mg/m(3))) as a ceiling for methylene bis(4-cyclohexylisocyanate). A worker's exposure to methylene bis(4-cyclohexylisocyanate) shall at no time exceed this ceiling level [NIOSH 1992]. * ACGIH TLV The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned methylene bis(4-cyclo-hexylisocyanate) a threshold limit value (TLV) of 0.005 ppm (0.054 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 26]. * Rationale for Limits The NIOSH limit is based on the risk of pulmonary irritation, respiratory effects and sensitization [NIOSH 1992]. The ACGIH limit is based on the risk of pulmonary irritation [ACGIH 1991, p. 996]. HEALTH HAZARD INFORMATION * Routes of Exposure Exposure to methylene bis(4-cyclohexylisocyanate) can occur through inhalation, ingestion, and eye or skin contact. * Summary of toxicology
* Emergency medical procedures: [NIOSH to supply] 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 methylene bis (4-cyclohexylisocyanate) and lead to worker exposures to this substance:
Good sources of information about control methods are as follows:
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 methylene bis(4-cyclohexylisocyanate) 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. * Pre-placement medical evaluation Before a worker is placed in a job with a potential for exposure to methylene bis(4-cyclohexylisocyanate), 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 respiratory system 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 methylene bis(4-cyclohexylisocyanate) 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 respiratory system 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 methylene bis(4-cyclo-hexylisocyanate) exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of methylene bis(4-cyclo-hexylisocyanate) on the respiratory system 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. * 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 methylene bis(4-cyclohexylisocyanate). WORKPLACE MONITORING AND MEASUREMENT Determination of a worker's exposure to airborne methylene bis (4-cyclohexylisocyanate) is made using a coated glass fiber filter (37 mm, open face). The filter coating is 1.0 mg 1-(2-pyridyl) piperazine. Samples are collected at a maximum flow rate of 1.0 liter/minute (ceiling) for a minimum sampling time of 15-minutes. The sample is then treated with 90/10 acetonitrile/dimethyl sulfoxide. Analysis is conducted by high performance liquid chromatography using an ultraviolet/fluorescence detector (HPLC/UV/FLU). This method is described in the OSHA Computerized Information System [OSHA 1994] and is partially validated.
PERSONAL HYGIENE PROCEDURES If methylene bis(4-cyclohexylisocyanate) contacts the skin, workers should immediately wash the affected areas with large amounts soap and water. Clothing contaminated with methylene bis(4-cyclo-hexylisocyanate) 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 methylene bis (4-cyclohexylisocyanate), particularly its potential for causing skin sensitization. A worker who handles methylene bis(4-cyclohexylisocyanate) 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 methylene bis(4-cyclohexylisocyanate) or a solution containing methylene bis(4-cyclohexylisocyanate) is handled, processed, or stored. STORAGE Methylene bis(4-cyclohexylisocyanate) 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 methylene bis(4-cyclohexylisocyanate) should be protected from physical damage and should be stored separately from alcohols, ethanol, amines, bases, acids, organotin catalysts, and chemically active metals [NIOSH 1994; NJDH 1986, p.3]. SPILLS AND LEAKS In the event of a spill or leak involving methylene bis (4-cyclohexylisocyanate), 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:
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 Methylene bis(4-cyclohexylisocyanate) 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 methylene bis (4-cyclohexylisocyanate); 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 methylene bis(4-cyclohexylisocyanate) 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 methylene bis(4-cyclohexylisocyanate) 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 methylene bis (4-cyclohexylisocyanate) 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 methylene bis(4-cyclohexylisocyanate). 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 methylene bis(4-cyclohexylisocyanate). There are no published reports on the resistance of various materials to permeation by methylene bis(4-cyclohexylisocyanate). To evaluate the use of PPE materials with methylene bis (4-cyclohexylisocyanate), 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 methylene bis(4-cyclohexylisocyanate). 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.
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. CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register. Lewis RJ, ed. [1993]. Lewis condensed chemical dictionary. 12th ed. New York, NY: Van Nostrand Reinhold Company. 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. 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 [1991]. Registry of toxic effects of chemical substances: Methylene bis(4-cyclohexylisocyanate). 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: Methylene bis (4-cyclohexylisocyanate). Trenton, NJ: New Jersey Department of Health. OSHA [1994]. Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration. Patnaik P [1992]. A comprehensive guide to the hazardous properties of chemical substances. New York, NY: Van Nostrand Reinhold. Sax NI, Lewis RJ [1989]. Dangerous properties of industrial materials. 7th ed. New York, NY: Van Nostrand Reinhold Company. Sittig M [1991]. Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications. USC. United States code. Washington, DC: U.S. Government Printing Office. Windholz M, ed. [1983]. Windholz Index 10th ed. Rahway, NJ: Windholz & Company.
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