August 21, 1978
DHHS (NIOSH) Publication Number 78-181
Current Intelligence Bulletin 27: Chloroethanes Review of Toxicity
In Bulletins #22 through #25 it was stated that the NIOSH National Occupational Hazard Survey (NOHS) had included "over 500,000 employees at 4,775 facilities." Actually the Survey included nearly 900,000 employees at 4,636 facilities.
In Bulletin #23 NIOSH erroneously listed Dowfume® MC-2 as a synonym for ethylene dibromide. Dow Chemical USA has advised NIOSH that Dowfume® MC-2 actually is 98% methyl bromide and 2% chloropicrin.
Chloroethanes: Review of Toxicity
The National Institute for Occupational Safety and Health (NIOSH) recommends that it would be prudent to handle 1,2-dichloroethane (ethylene dichloride); 1,1,2- trichloroethane; 1,1,2,2-tetrachloroethane; and hexachloroethane in the workplace as if they were human carcinogens. This recommendation is based primarily on consideration of National Cancer Institute (NCI) data indicating that laboratory animals administered these compounds experienced a statistically significant excess of cancer as compared to control animals.1-4 Additionally, NIOSH recommends that five other chloroethane compounds: chloroethane* (ethyl chloride); 1,1-dichloroethane; 1,1,1-trichloroethane (methyl chloroform); 1,1,1,2-tetrachloroethane; and pentachloroethane be closely monitored for carcinogenic effects in humans and/or laboratory animals. These five should also be treated in the workplace with caution because of their relation to the four chloroethanes shown to be carcinogenic in laboratory animals.
This Current Intelligence Bulletin summarizes information on some of the similarities and dissimilarities within the chloroethane group. NIOSH is concerned about the carcinogenic potential of chloroethanes based on emerging data from the NCI bioassay program. Concern for the carcinogenic potential of all members of the chloroethane series is based upon structural similarities within the group as well as the structural similarities to other carcinogenic organochlorine compounds. Extreme care must be used when selecting possible substitutes, and the alternatives should be fully evaluated with regard to human effects.
At present, NIOSH is not aware of any evidence associating chloroethane compounds with an increased risk of cancer in man. However, animal studies are valuable in helping identify human carcinogens. Substances that cause cancer in experimental animals must be considered a potential cancer risk in man. Safe levels of exposure to carcinogens have not been demonstrated, but lowered exposure to carcinogens decreases the probability of cancer development.
NIOSH issued Current Intelligence Bulletin #25 (April 1978), recommending that ethylene dichloride (1,2-dichloroethane) be handled in the workplace as if it were a human carcinogen.5 NIOSH is now distributing Bulletin #27 to advise of additional findings of the NCI chloroethane bioassays, other pertinent data, and possible implications for occupational health. Also included are "Suggested Guidelines for Controlling Employee Exposure to Chloroethanes." NIOSH requests that producers, distributors, professional associations, and unions transmit the information in this Bulletin to their custorners, employees, associates and members.
Table 1. Summary of Some of the Industries and Occupations Which Use Chloroethanes.a
|monochloroethane||medical and other health services; automotive dealers and service stations; wholesale trade; electric, gas and sanitary services; machinery, except electrical; special trade contractors; fabricated metal products; printing and publishing; rubber and plastics products not elsewhere classified; food and kindred products||registered nurses; automobile mechanics; physicians, medical and osteopathic; office machine mechanics and repairmen; garage workers and gas station attendants; not specified mechanics and repairmen; household appliance and accessory installers; assemblers; heavy equipment mechanics, including diesel; plumbers and pipe fitters|
|1,1-dichloroethane||chemicals and allied products; miscellaneous business services; stone, clay and glass products not elsewhere classified; petroleum and coal products||janitors and sextons; not specified clerical workers; electricians; assemblers; agricultural and biological technicians|
|1,2-dichloroethane||medical and other health services; automotive dealers and service stations; machinery, except electrical; wholesale trade; printing and publishing; eating and drinking places; primary metal industries; chemicals and allied products; miscellaneous business services; transportation equipment; electrical equipment and supplies; special trade contractors; fabricated metal products; stone, clay and glass products; food and kindred products; paper and allied products; rubber and plastics products not elsewhere covered; communication; water transportation; instruments and related products||automobile mechanics; janitors and sextons; heavy equipment mechanics, including diesel; registered nurses; miscellaneous specified machine operatives; miscellaneous operatives; assemblers; machinists; pressmen and plate printers, printing; cooks, except private household; garage workers and gas station attendants; cleaners and charwomen; electricians; telephone installers and repairmen; vehicle washers and equipment cleaners; secretaries not elsewhere classified; nursing aides, orderlies and attendants; checkers, examiners and inspectors, manufacturing; not specified mechanics and repairmen: printers, manufactured articles|
|1,1,1-trichloroethane||medical and other health services; automotive dealers and service stations; machinery, except electrical; wholesale trade; transportation equipment; printing and publishing; primary metal industries; electrical equipment and supplies; fabricated metal products; communication; special trade contractors; chemicals and allied products; eating and drinking places; miscellaneous services; transportation by air; stone, clay and glass products; retain general merchandise; instruments and related products; apparal and accessory stores; electric, gas and sanitary services; food and kindred products; rubber and plastics products not elsewhere classified; personal services; paper and allied products||auto mechanics; janitors and sextons; heavy equipment mechanics, including diesel; registered nurses; secretaries not elsewhere classified; machinists; machine operatives; miscellaneous specified; assemblers; not specified clerical workers; cleaners and charwomen; miscellaneous operatives; electricians; pressmen and plate printers, printing; garage workers and gas station attendants; telephone installers and repairmen; manufacturing checkers, examiners and inspectors; cooks, except private household; tool and die makers; administrators and managers, not elsewhere classified; nursing aides, orderlies and attendants; dishwashers; vehical washers and equipment cleaners; millwrights; miscellaneous mechanics and repairmen; office machine|
|1,1,2-trichloroethane||primary metal industries; wholesale trade; auto repair, services and garages; transportation equipment; communication; electrical equipment and supplies; special trade contractors; miscellaneous retail stores; machinery, except electrical; stone, clay and glass products; chemicals and allied products; medical and other health services; instruments and other related products||electricians; heavy equipment mechanics, including diesel; miscellaneous mechanics and repairmen; upholsterers; janitors and sextons; electrical and electronic engineering technicians; office machine mechanics and repairmen; radio and television; not specified mechanics and repairmen; air conditioning, heating and refrigeration; telephone installers and repairmen; miscellaneous operatives; assemblers; manufacturing checkers, examiners and inspectors; printing pressmen and plate printers|
|1,1,2,2-tetrachloroethane||electrical equipment and supplies; chemicals and allied products; electric, gas and sanitary services; miscellaneous business services; stone, clay and glass products||assemblers; janitors and sextons; not specified clerical workers; electricians; manufacturing checkers, examiners and inspectors|
|hexachloroethane||real estate; paper and allied products; lumber and wood products; amusement and recreation services not elsewhere classified||cleaners and charwomen; millwrights; machine operatives, miscellaneous specified; plumbers and pipefitters; electricians|
(a) 1,1,1,2-tetrachloroethane and pentachloroethane were not mentioned in the NOHS survey6 [return to table]
(b) These are standard industrial titles from the Standard Industrial Classification Manual7 [return to table]
(c) These are standard occupational titles from the Burea of the Census8 [return to table]
Chloroethanes are chlorinated organic compounds structurally related to ethane in which one or more of the hydrogen atoms have been replaced by a chlorine atom or atoms. Monochloroethane, for example, is shown to result from the replacement of one hydrogen atom in ethane by a chlorine atom.
At room temperature monochloroethane is a gas, hexachloroethane is a solid, and the seven other chloroethanes are liquids. Some of the chloroethanes are manufactured on a large scale and used extensively because of their low cost and excellent solvent properties. They are used as solvents and in degreasing agents, cutting fluids, fumigants, and in the manufacture of plastics, textiles, and other chemicals. Table 1 summarizes the major industries and occupations in which workers are potentially exposed to chloroethanes.
From 1972-1974, NIOSH conducted the NIOSH National Occupational Hazards Survey (NOHS), on a sample of about 900,000 employees at 4,636 facilities, in order to determine the potential for worker exposure to chemicals and physical agents. NOHS algorithms used Bureau of the Census 1970 population counts to permit extrapolation from the sample to the United States worker population of 1970. A total of over 3 million workers were estimated to be potentially exposed to one or more chloroethanes. Table 2 presents a summary of NOHS estimates of worker exposure to chloroethanes and some production figures.6,9,40
|Chemical||Estimated Number of Workers Exposed||Annual Production Quantities (pounds)|
(a) NOHS estimates not available [return to table]
(b) does not appear to be commercially produced in the United States [return to table]
(c) direct production information not available [return to table]
(d) 73O,OOO kg were imported in 1976 [return to table]
Summaries of the current Department of Labor - Occupational Safety and Health Administration (OSHA) exposure standards10 and NIOSH recommended exposure standards for the chloroethane compounds are given in Table 3.
Table 3. Chloroethane Exposure Standards.
|Chemical||OSHA Exposure Standard (ppm)||NIOSH Recommended Exposure Standard (ppm)|
* NIOSH has tentative plans for a Criteria Document for a Recommended Standard for this substance
The OSHA exposure standards and the NIOSH recommended standards and control measures for the chloroethanes were developed before the carcinogenic potential of these compounds was recognized. Therefore, an assessment of the carcinogenicity of these compounds was not included. The levels currently recommended or adopted may not provide adequate protection from potential carcinogenic effects.
Laboratory Animal Studies
As of July 1978, four of the eight chloroethanes selected by NCI for testing have been shown to be carcinogenic in laboratory animals. The results of the bioassays1-4,14 are summarized in Table 4. Each compound was studied separately in male and female Osborne-Mendel rats and male and female B6C3F1 mice. Each experiment consisted of a high dose and a low dose group of 50 animals each. Twenty animals of each species/sex combination served as untreated controls and 20 animals of each species/sex combination served as vehicle controls. The chloroethane compounds were administered to the test animals in a corn oil vehicle by gastric intubation (stomach tube) five days a week for 78 weeks. The vehicle controls were intubated with pure corn oil at the same rate as the high dose animals.
|Compound||Species/Sex||Tumor Site||Statistically Significant Tumors|
|monochloroethane||no testing planned|
|1,1-dichloroethane||retesting recommended because initial results inconclusive|
|rats/male||forestomach||squamous cell carcinomas|
|1,1,1-trichloroethane||retesting in progress|
|1,1,1,2-tetrachloroethane||testing in progress, no report available|
|pentachloroethane||testing in progress, no report available|
The National Cancer Institute has concluded that under the conditions of the bioassay 1,2-dichloroethane; 1,1,2-trichloroethane; 1,1,2,2-tetrachloroethane; and hexachloroethane are carcinogenic in mice, inducing liver cancer in both sexes.1-4 Additionally, results of the NCI bioassay of 1,2-dichloroethane indicate that this compound also causes cancer in male and female rats. In mice 1,1,2-trichloroethane was also associated with increased adrenal pheochromocytoma, a tumor which gives rise to high blood pressure and hyperglycemia. Toxic kidney damage was observed in all groups of both mice and rats treated with hexachloroethane.4
Although the occurence of cancer in mice is highly significant, the results do not provide conclusive evidence that 1,1,2-trichloroethane; 1,1,2,2-tetrachloroethane; or hexachloroethane cause cancer in rats. A statistically significant association between increased dosage and accelerated mortality was observed in rats treated with hexachloroethane. NCI has concluded that early mortality may have obscured a carcinogenic effect in these animals.
The National Cancer Institute is currently conducting bioassays of pentachloroethane and 1,1,1,2-tetrachloroethane.14 They are also retesting 1,1-dichloroethane and 1,1,1-trichloroethane because the previous tests were inconclusive; low survival rates complicated the interpretation of the bioassay results. Monochloroethane has not yet been tested.
Other Adverse Effects
All of the chloroethane compounds are known to cause central nervous system (CNS) depression in laboratory animals. This is usually expressed as abnormal weakness, intoxication, restlessness, irregular respiration, muscle incoordination, and unconsiousness. Chloroethanes are generally irritating to the eyes and skin. Damage to the liver and/or kidney has been demonstrated in various animal species following exposure to these compounds.15
It has been reported that some of the chloroethanes and their metabolites are mutagenic in bacterial systems.3,16 Mutagenic activity per se, should be considered a substantial liability. In addition, research suggests a correlation between mutagenicity in some bacterial strains and carcinogenicity in higher animals. Other adverse effects of the chloroethanes may vary from one compound to another. Table 5 summarizes some of the toxicological studies in animal systems.
|monochloroethane||unspecified||kidney damage; fatty changes in liver, kidney, and heart|
|rat||liver injury; retarded fetal development|
|cat||retarded growth rate, fatty changes in liver; heart dilation; lung hyperemia|
|dog||corneal clouding; fatty changes in liver liver enlargement; weight loss|
|guinea pig||fatty changes in liver; liver enlargement; weight loss|
|monkey||fatty changes in liver|
|rabbit||fatty changes in liver; hypotension; respiratory paralysis; EKG changes; anemia; bone marrow changes; liver dysfunction, hemorrhage and degeneration; kidney degeneration and dysfunction|
|rat||embryotoxin; pulmonary congestion; fatty changes in liver|
|1,1,1-trichloroethane||cat||neuromuscular reflex changes|
|dog||sudden death; respiratory failure|
|guinea pig||fatty changes in liver; lung irritation|
|mouse||cardiac arrythmias; liver dysfunction; pulmonary congestion|
|monkey||cardiac arrythmias; myocardial depression respiratory failure; staggering gait; tachycardia; tremors|
|rat||cardiac failure; pulmonary congestion; pneumonitis; staggering gait; weakness; respiration; semiconsciousness; respiratory failure|
|dog||liver and kidney injury|
|guinea pig||liver and kidney injury|
|rat||embryotoxin; liver dysfunction; mutagen|
|dog||ascites; diarrhea; jaundice; liver enlargement; intestinal hemorrhage|
|guinea pig||convulsions; weight loss; death|
|monkey||anorexia; diarrhea; blood cell fluctuation; weight loss|
|mouse||staggering gait; breathing difficulty; fatty degeneration of liver and kidney; death|
|rabbit||altered immune system; altered blood chemistry; liver and kidney degeneration; fatty degeneration of liver and kidney; corneal reflex changes; liver enlargement; paralysis; death|
|rat||blood cell changes; fatty degeneration of liver; liver dysfunction; death|
|pentachloroethane||cat||liver, kidney, and lung changes|
|dog||fatty degeneration of liver; kidney and lung injury|
|hexachloroethane||cattle||liver and kidney dameage|
|mouse||liver and kidney damage|
|rat||liver and kidney damage|
|sheep||liver and kidney damage|
Although chloroethanes have been associated with cancer in laboratory animals, NIOSH is unaware of any definitive evidence indicating that chloroethanes are carcinogenic in humans. However, the chloroethanes have long been known to be capable of producing harmful local and systemic effects. As summarized in Tables 6 and 7, the chloroethanes may affect a variety of human organs or systems. The effects of chloroethane exposure vary from one compound to another, but, most are known to effect the central nervous system (CNS). In many instances, the clinical manifestations and laboratory findings associated with chloroethane toxicity are similar for the major routes of entry: inhalation, skin absorption, and ingestion. Liver and/or kidney injury, pulmonary irritation, and damage to the blood-forming system have been associated with inhalation of chloroethanes. Repeated or prolonged skin exposure can defat the skin and cause dermatitis.
In addition to the toxic effects of chloroethanes and their metabolites, the oxidative decomposition of products produced in the presence of open flames, hot metals, or lighted cigarettes should be taken into account. The chloroethane compounds may degrade to phosgene, hydrogen chloride and dichloroacetylene. Phosgene is considered to be dangerous to life in 30 to 60 minutes at 12.5 ppm.37
|1. Immunological Allergic
5. Renal Urologic
7. Hepatic Billiary
* adverse human health effects have not been reported to NIOSH for 1,1,2-trichloroethane, 1,1,1,2-tetrachloroethane, and pentachloroethane [return to table]
|monochloroethane||neurologic||central nervous system depression, headache, dizziness, incoordination, feeling inebriated, unconsciousness|
|respiratory||respiratory tract irritation, respiratory failure|
|cardiovascular||cardiac arrhythmias, cardiac arrest|
|dermatological||skin irritation, frostbite, allergic eczema|
|other||eye irritation, death|
|1,1-dichloroethane||neurologic||central nervous system depression|
|respiratory||respiratory tract irritation|
|1,2-dichloroethane||neurologic||headache, dizziness, unconsciousness, vertigo, hand tremors, generalized weakness, sleepiness, nervousness, mental confusion|
|hepatic||liver function abnormalities, cellular damage, toxic chemical hepatitis, jaundice, liver enlargement|
|1, 1, 1-trichloroethane||neurologic||central nervous system depression, headache, dizziness, incoordination, feeling inebriated, unconsciousness; impaired perceptual speed, manual dexterity and equilibrium; increased reaction time, lightheadeness, drowsiness, sleepiness, generalized weakness, ringing sound in ears, unsteady gait, burning and/or prickling sensation in hands and/or feet|
|hepatic||cellular damage, liver function abnormalities|
|gastrointestinal||nausea, vomiting, diarrhea|
|cardiovascular||drop in blood pressure (hypotension), decrease in heart rate (bradycardia), cardiac arrhythmias|
|hematologic||blood clotting changes|
|dermatologic||dryness, cracking, scaliness, inflammation|
|other||eye irritation, fatigue, death|
|1,1,2-trichloroethane||NIOSH is unaware of reports of adverse occupational exposure (see Table 5)|
|1,1,1,2-tetrachloroethane||NIOSH is unaware of reports of adverse occupational exposure (see Table 5)|
|1,1,2,2-tetrachloroethane||neurologic||central nervous system depression, headache, feeling inebriated, consciousness, drowsiness, unsteady gait, vertigo, hand tremors, numbness in limbs, prickling sensation of fingers and toes, pain in sole of feet, loss of knee jerk, paralysis of some muscles of the hands and feet, inflammation of the peripheral nerves slight paralysis of the soft palate, loss of the gag reflex, irritability, mental confusion, delirium, convulsions, stupor, coma|
|hepatic||liver function abnormalities, massive cell damage toxic chemical hepatitis, jaundice, liver enlargement, sensation of pressure in the liver area|
|gastrointestinal||abdominal pain, nausea, vomiting, unpleasant taste in the mouth, loss of appetite (anorexia), vomiting of blood (hematemesis), increased flatulence, diarrhea, constipation, pale stools|
|urologic||kidney damage, presence of bile pigments, albumen, and casts in the urine|
|respiratory||excessive fluid in the lungs (pulmonary edema), respiratory paralysis|
|cardiovascular||fatty degeneration of the heart muscle (in lab animals)|
|hematologic||anemia, increase in white blood cells, (and blood platelets)|
|dermatologic||dryness, cracking, scaliness, inflamation, purpuric rash|
|other||insomnia, general malaise, fatigue, excessive sweating, weight loss|
|pentachloroethane||NIOSH is unaware of reports of adverse occupational exposure (see Table 5)|
|hexachloroethane||neurologic||inability to close eyelid|
|eye irritation, tearing of eyes, inflamation of delicate membrane lining the eye, visual intolerance to light, (photophobia)|
Animal studies are valuable in helping identify human carcinogens. Substances that cause cancer in experimental animals must be considered a potential cancer risk in man. Although safe levels of exposure to carcinogens have not yet been demonstrated decreasing exposure to carcinogens does reduce their probability of initiating cancer development.
As an interim and prudent measure while the carcinogenicity of chloroethanes is being further evaluated NIOSH recommends that occupational exposure to 1,2-dichloroethane; 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, and hexachloroethane be minimized. Exposures should be limited to as few employees as possible, while minimizing workplace exposure levels with engineering and work practice controls. Additionally, monochloroethane; 1,1-dichloroethane; 1,1,1-trichloroethane; 1,1,1,2-tetrachloroethane; and pentachloroethane should be treated in the workplace with caution.
J. Michael Lane, M.D.
* to be referred to as monochloroethane in this Bulletin [return to text]
- National Cancer Institute. Bioassay of 1,2-Dichloroethane for Possible Carcinogenicity. U.S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Cancer Institute, Carcinogenesis Testing Program, DHEW Publication No. (NIH) 78-1305, January 10, 1978.
- National Cancer Institute. Bioassay of 1,1,2-Trichloroethane for Possible Carcinogenicity. U.S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Cancer Institute, DHEW Publication No. (NIH) 78-1324, 1978.
- National Cancer Institute. Bioassay of 1,1,2,2-Tetrachloroethane for Possible Carcinogenicity. U.S. Department of Health, Education and Welfare, Public Health Service, National Institutes of Health, National Cancer Institute, DHEW Publication No. (NIH) 78-827, 1978.
- National Cancer Institute. Bioassay of Hexachloroethane for Possible Carcinogenicity. U.S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Cancer Institute, DHEW Publication No. (NIH) 78-1318, 1978.
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- Private Correspondence from SRI International, Menlo Park, California, June 29, 1978.
- United States Department of Labor, Occupational Safety and Health Administration. General Industry Standards (29 Code of Federal Regulations 1910), January, 1976.
- National Institute for Occupational Safety and Health. Criteria for a Recommended Standard . . . . Occupational Exposure to Ethylene Dichloride (1,2-Dichloroethane). U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 76-139, March, 1976.
- National Institute for Occupational Safety and Health. Criteria for a Recommended Standard .... Occupational Exposure to 1,1,1-Trichloroethane (Methyl Chloroform). U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 76-184, July, 1976.
- National Institute for Occupational Safety and Health. Criteria for a Recommended Standard . . . . Occupational Exposure to 1,1,2,2-Tetrachloroethane. U.S. Department Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 77-121, December, 1976.
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- Fishbein, L.: Industrial mutagens and potential mutagens I. halogenated aliphatic derivatives. Mutation Research 32:2176-308, 1976.
- Shmuki, L.M.: The effect of chronic exposure to low concentrations of chlorinated ethane-series hydrocarbons on specific and nonspecific immunological response in animals under experimental conditions. Gigiena Truda I Professionalyne Zabolevania (8): 38-43, 1977.
- McCann, J., Simmon, V., Streitwieserp D., Ames, B.N.: Mutagenicity of chloroacetaldehyde, a possible metabolic product of 1,2-dichloroethane (ethylene dichloride), chlorethanol (ethylene chlorohydrin), vinyl chloride, and cyclophosphamide. Proceedings of the National Academy of Sciences of the U.S.A. 72(8): 3190-3193, August, 1975.
- Smyth, H.F., Cummings, D.E.: Halogenated hydrocarbons: I. aliphatic. IN: Patty, F.A. Industrial Hygiene and Toxicology Second Revised Edition, Volume II. New York, John Wiley and Sons, Inc., 1963.
- Schwetz, B.A., Leong, B.K., Gehring, P.J.: Embryo and fetotoxicity of inhaled carbon tetrachloride, 1,1-dichloroethane and methyl ethyl ketone in rats. Toxicology and Applied Pharmacology 28(3): 452-464, June, 1974.
- Hofmann, H.T., Birnstiel, H., Jobst, P.: Zur Inhalation Toxicitat von 1,1 und 1,2-Dichorathan (on the inhalation toxicity of 1,1- and 1,2-dichloroethane). Archiv fur Toxikologie 27(3): 248-265, 1971.
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Suggested Guidelines for Controlling Employee Exposure to Chloroethanes
NIOSH recommends that it would be prudent to handle 1,2-dichloroethane (ethylene dichloride); 1,1,2-trichloroethane; 1,1,2,2-tetrachloroethane; and hexachloroethane in the workplace as if they were human carcinogens. Exposure to these chloroethanes should be limited to as few employees as possible, and workplace exposure levels should be minimized. The areas in which they are used should be restricted to only those employees essential to the process or operation and these employees should be adequately protected.
Additionally, NIOSH recommends that the other five chloroethane compounds: monochloroethane (ethyl chloride); 1,1-dichloroethane; 1,1,1-trichloroethane (methyl chloroform); 1,1,1,2-trichloroethane; and pentachloroethane should be treated in the workplace with caution because of their relation to the four chloroethanes shown to be carcinogenic in laboratory animals. These five chloroethanes should be closely monitored for carcinogenic effects in humans.
Detailed sampling and analytic methods for most of the chloroethane exposure measurements are described in the NIOSH Manual of Analytical Methods, Second Edition.1 These are:
|1,2-dichloroethane||P&CAM 127 and S122|
|1,1, 1-trichloroethane||P&CAM 127 and S328|
|1,1, 2-trichloroethane||P&CAM 127 and S134|
Initial and routine employee exposure surveys should be made by competent industrial hygiene and engineering personnel. These surveys are necessary to determine the extent of employee exposure and to ensure that controls are effective.
The NIOSH Occupational Exposure Sampling Strategy Manual2 may be helpful in developing efficient programs to monitor employee exposures to chloroethanes. The manual discusses determination of the need for exposure measurements, selection of appropriate employees for exposure evaluation and selection of sampling times.
Employee exposure measurements should primarily consist of 8-hour TWA (time-weighted average) exposure estimates calculated from personal or breathing zone samples (air that would most nearly represent that inhaled by the employees). In addition, short term samples should be taken during periods of maximum expected exposure by using all available knowledge regarding the area, employee work procedures, and process. Area and source measurements may be useful to determine problem areas, processes and operations.
Controlling Employee Exposure
There are four basic methods of limiting employee exposure to chloroethanes. None of these is a simple industrial hygiene or management decision and careful planning and thought should be used prior to implementation.
The substitution of an alternative material with a lower potential health risk is one method. However, extreme care must be used when selecting possible substitutes. Alternatives to chloroethanes should be fully evaluated with regard to possible human effects. Unless the toxic effects of the alternative have been thoroughly evaluated a seemingly safe replacement, possibly only after years of use, may be found to induce serious health effects.
The most effective control of chloroethanes, where feasible, is at the source of contamination by enclosure of the operation and/or local exhaust ventilation. Guidelines for selected processes and operations can be found in the NIOSH Recommended Industrial Ventilation Guidelines.3
If feasible, the process or operation should be enclosed with a slight vacuum so that any leakage will result in the flow of external air into the enclosure.
The next most effective means of control would be a well designed local exhaust ventilation system that physically encloses the process as much as possible, with sufficient capture velocity to keep the contaminant from entering the work atmosphere. To ensure that ventilation equipment is working properly, effectiveness (e.g., air velocity, static pressure, or air volume) should be checked at least every three months. System effectiveness should be checked soon after any change in production, process, or control which might result in significant increases in airborne exposure to chloroethanes.
A third alternative is the isolation of employees. It frequently involves the use of automated equipment operated by personnel observing from a closed control booth or room. The control room is maintained at a greater air pressure than that surrounding the process equipment so that air flow is out of, rather than into, the room. This type of control will not protect employees who must do process checks, adjustments maintenance, and related operations.
Personal Protective Equipment
The least preferred method is the use of personal protective equipment. This equipment, which may include respirators, goggles, gloves, etc., should not be used as the only means to prevent or minimize exposure during routine operations.
Exposure to chloroethanes should not be controlled with the use of respirators except:
- During the time period necessary to install or implement engineering or work practice controls; or
- In work situations in which engineering and work practice controls are technically not feasible; or
- For maintence; or
- For operations which require entry into tanks or closed vessels; or
- In emergencies.
Only respirators approved by the National Institute for Occupational Safety and Health (NIOSH) under the provisions of Federal regulations 30 CFR 11 should be used. Refer to Cumulative Supplement June 1979 NIOSH Certified Equipment4 for a listing of NIOSH-approved respirators. Note that the use of faceseal coverlets or socks with respirators voids NIOSH approvals.
Quantitative faceseal fit test equipment (such as sodium chloride dioctyl phthalate, or equivalent) should be used. Refer to NIOSH's A Guide to Industrial Respiratory Protection5 for guidelines on appropriate respiratory protection programs.
In addition, proper maintenance procedures, good housekeeping in the work area, and employee education are all vital aspects of a good control program. Employees should be informed as to the nature of the hazard, its control, and appropriate personal hygiene procedures.
References for Suggested Guidelines
- NIOSH Manual of Analytical Methods, 2nd Edition, Vol. 1: GPO #017-033-00-267-3, $8.75: Vol. 2: GPO #017-033-00260-6, $9.75; Vol. 3: GPO #017-033-0247-9 $9.00.
- NIOSH Occupational Exposure Sampling Strategy Manual, GPO #017-033-00247-9, $2.75.
- NIOSH Recommended Industrial Ventilation Guidelines, GPO #017-033-00136-7, $3.90.
- NIOSH Cummulative Supplement June 1977, NIOSH Certified Equipment, NIOSH #77-195, no charge.
- A Guide to Industrial Respiratory Protection, GPO #017-033-00153-7, $2.30.
|GPO publications must be ordered from:||Superintendent of Documents
U.S. Government Printing Office
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|Reference #4 can be ordered from:||Publications Dissemination, DTS
4676 Columbia Parkway
Cincinnati, Ohio 45226
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 75-00-3
NIOSH RTECS.Number KH75250
Chemical Formula C2H5C1
|Aethylis Chloridum||Ethane, Chloro-|
|Chloryl Anesthetic||Muriatic Ether|
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 75-34-3
NIOSH RTECS Number KI01750
Chemical Formula C2H4Cl2
|Chlorinated Hydrochloric Ether||Ethylidene Chloride|
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 107-06-2
NIOSH RTECS Number KI05250
Chemical Formula C2H4Cl2
|Destruxol Borer-Sol||ENT 1,656|
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 71-55-6
NIOSH RTECS Number KJ29750
Chemical Formula C2H3Cl3
|Chloroethene NU||Methyl Chloroform|
IDENTIFIEERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 79-00-5
NIOSH RTECS Number KJ31500
Chemical Formula C2CH3Cl3
|Ethan Trichloride||1, 1, 2-Trichloroethane|
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 630-20-6
NIOSH RTECS Number KI8450000
Chemical Formula C2H2Cl4
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 79-34-5
NIOSH RTECS Number KI85750
Chemical Formula C2H2Cl4
IDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 76-01-7
NIOSH RTECS Number KI63000
Chemical Formula C2HCl5
INDENTIFIERS AND SYNONYMS FOR
Chemical Abstracts Service Registry Number 67-72-1
NIOSH RTECS Number KI40250
Chemical Formula C2Cl6
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