Chloroform
|
Introduction |
This guideline summarizes pertinent information about
chloroform 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Recommendations may be superseded by new developments in these fields; readers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.
|
Recognition |
SUBSTANCE IDENTIFICATION
* Formula
CHCl(3)
* Structure
(For Structure, see paper copy)
* Synonyms
Trichloromethane, trichloroform, freon 20, COBEHN
Spray-Cleaner solvent, formyl trichloride, methane trichloride, methenyl
trichloride, methyl trichloride
* Identifiers
1. CAS No.: 67-66-3
2. RTECS No.: FS9100000
3. DOT UN: 1888 55
4. DOT label: Poison
Chloroform is a clear, colorless, and mobile liquid with a
pleasant, sweet odor. Air odor threshold concentrations ranging from 85 to 307
parts per million (ppm) parts of air have been reported for chloroform.
CHEMICAL AND PHYSICAL PROPERTIES
* Physical data
1. Molecular weight: 119.4
2. Boiling point (at 760 mm Hg): 62 degrees C
(143 degrees F)
3. Specific gravity (water = 1): 1.48 at 20 degrees C
(68 degrees F)
4. Vapor density: 4.1
5. Melting point: - 63.5 degrees C (- 82 degrees F)
6. Vapor pressure at 20 degrees C (68 degrees F):
160 mm Hg
7. Solubility: Slightly soluble in water; soluble in alcohol, ether, acetone, benzene, and ligroin.
8. Evaporation rate: Data not available.
* Reactivity
1. Conditions contributing to instability: Heat, air, and light.
2. Incompatibilities: Contact between chloroform and acetone, alkalis, and chemically active metals such as aluminum magnesium (in powder form), sodium, or potassium should be avoided. Chloroform is also incompatible with dinitrogen tetraoxide, fluorine, triisopropylphosphine, and solid potassium tert-butoxide.
3. Hazardous decomposition products: Toxic gases and vapors such as hydrogen chloride, chlorine, phosgene, and carbon monoxide may be released in a fire involving chloroform.
4. Special precautions: None reported.
* Flammability
1. Flash point: Not applicable.
2. Autoignition temperature: Not applicable.
3. Flammable limits in air: Not applicable.
4. Extinguishant: Use an extinguishant that is suitable
for the materials involved in the surrounding fire.
Fires involving chloroform 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. Containers of chloroform
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 fire exposed
containers from the sides with water until well after the fire is out. Stay
away from the ends of containers. Dike fire control water for later disposal;
do not scatter this material. Firefighters should wear a full set of protective
clothing and self-contained breathing apparatus when fighting fires involving
chloroform.
EXPOSURE LIMITS
* OSHA PEL
The current Occupational Safety and Health Administration
(OSHA) permissible exposure limit (PEL) for chloroform is 50 ppm (240
milligrams per cubic meter (mg/m(3))) as a ceiling limit. A worker's exposure
to chloroform shall at no time exceed this ceiling level [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 chloroform of 2
ppm (9.78 mg/m(3)) as a 60-minute short-term exposure limit (STEL). NIOSH also
considers chloroform a potential occupational carcinogen [NIOSH 1992].
* ACGIH TLV
The American Conference of Governmental Industrial
Hygienists (ACGIH) has assigned chloroform a threshold limit value (TLV) of 10
ppm (49 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek.
The ACGIH also considers chloroform a suspected human carcinogen (A2 substance)
[ACGIH 1994, p. 16].
* Rationale for Limits
The NIOSH limit is based on the risk of central nervous
system effects and potential for cancer; cancer of the liver and kidneys in
animals [NIOSH 1992].
The ACGIH limit is based on the risk of cancer [ACGIH
1991, p. 290].
|
Evaluation |
HEALTH HAZARD INFORMATION
* Routes of Exposure
Exposure to chloroform can occur through inhalation, ingestion, or contact with the skin or eyes [Sittig 1991].
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* Summary of toxicology
1. Effects on Animals:
Chloroform is a central nervous system depressant and carcinogen. Exposure of pregnant animals to chloroform increases the rate of fetal loss and malformation [Patnaik 1992]. The acute toxicity of chloroform is species-, strain-, sex-, and age-dependent. The oral LD(50) in young and older adult male Sprague-Dawley rats are 1,336 and 1,188 mg/kg; in 14-day-old rats of the same species, the oral LD(50) is 445 mg/kg [Clayton and Clayton 1982]. The dermal LD(50) in rabbits is greater than 20 gm/kg [NIOSH 1995]. Males of many mouse strains are susceptible to kidney damage, but not the females. Liver damage was the cause of death in rats and mice after acute exposures [Clayton and Clayton 1982]. Two chronic studies of rats show that chloroform-induced kidney and liver damage begins to appear at the 50 ppm exposure level and the severity of the exposure-related effects increases with dose [NLM 1995]. Chloroform was tested for carcinogenicity in three experiments in mice and one in rats. It produced liver cancer in mice, kidney tumors in male rats, and thyroid tumors in female rats [ACGIH 1991]. The International Agency for Research on Cancer (IARC) has concluded that chloroform is a carcinogen in experimental animals [IARC 1987]. Chloroform is both embryotoxic and teratogenic in experimental animals. Embryotoxic effects include decreased conception rate, fetal resorption, retarded fetal development, and small size [ACGIH 1991]. In another study, there was a significant incidence of cleft palate in the offspring of exposed pregnant mice [Clayton and Clayton 1982]. Chloroform crosses the placenta rapidly and enters the fetal circulation [NLM 1995]. Chloroform applied to rabbit skin caused redness and necrosis. Liquid chloroform instilled into rabbit eyes caused conjunctivitis and injury to the cornea [Clayton and Clayton 1982].
2. Effects on Humans: The toxicity of chloroform is well understood because of its long history of use as an anesthetic. Inhalation of 10,000 ppm of chloroform vapor produces clinical anesthesia. Inhalation of higher doses causes cardiovascular depression, with death resulting from ventricular fibrillation. Delayed death is associated with liver necrosis [ACGIH 1991]. Chronic inhalation of chloroform may cause psychiatric and neurological symptoms, including depression, hallucinations, and moodiness [NLM 1995]. In studies with human volunteers, exposure to 4,100 ppm causes serious disorientation, and 1,000 ppm caused dizziness, nausea, and after effects of fatigue and headache. Exposures of 20 to 70 ppm for undefined lengths of time caused less extreme, but still evident, effects on the central nervous system [Hathaway et al. 1991]. Liver enlargement was demonstrated in 17 of 68 workers exposed to chloroform at concentrations of 10 to 200 ppm for 1 to 4 years. Among other factors that increase the toxic effects of chloroform is ethanol [Hathaway et al. 1991]. As a result, alcoholics react more severely to exposure [Genium 1992]. Exposure to high concentrations of chloroform vapor causes redness and twitching of the eyes. Liquid chloroform splashed into the eye causes immediate burning, pain, and possible injury to the cornea. The eye returns to normal in 1 to 3 days [Grant 1986]. Application of chloroform to the skin causes burning, pain, redness, and vesiculation. Based on experimental animal studies, IARC has concluded that chloroform should be regarded as a cancer risk to humans. One study of people exposed to chloroform in their drinking water showed a correlation between chloroform concentration and rectal and bladder cancer [Hathaway et al. 1991].
1. Acute exposure:
Inhalation of chloroform causes signs and symptoms of central nervous system depression. In the initial stages, there is a feeling of warmth of the face and body, then irritation of the mucous membranes, eyes, and skin, followed by excitation, loss of reflexes, sensation, and consciousness. The pupils dilate and have a reduced reaction to light. Prolonged inhalation causes paralysis, cardiac and respiratory failure, and death [Sax and Lewis 1989; Genium 1992]. Other symptoms may include digestive upset, mental dullness, and dizziness [Sittig 1991]. Chloroform vapors may irritate the eyes and skin. Chloroform liquid causes burning of the eye and transient corneal injury. Skin exposure results in burning and redness [NLM 1995]. Exposure of pregnant women to chloroform may result in fetal death or malformation based on animals studies [Clayton and Clayton 1982].
2. Chronic exposure:
Chronic exposure to chloroform causes neurological and gastrointestinal signs and symptoms that resemble those of chronic alcoholism [Parmeggiani 1983]. These may include depression, liver enlargement, and gastrointestinal disorders [Sittig 1991]. Chronic skin exposure to chloroform may leave the skin red, dry, and cracking [Genium 1992].
EMERGENCY MEDICAL PROCEDURES
* 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 chloroform and
lead to worker exposures to this substance
- The manufacture and transportation of chloroform
- Used in manufacture of fluorocarbons(especially chlorodifluoromethane) for refrigerants and aerosol propellants; used in fire extinguishers to lower the freezing temperature of carbon tetrachloride; used in manufacture of fluorocarbon resins, tribromomethane, plastics, and thermally stable polymers; used in the manufacture of artificial silk, floor polishes, dyes, and pesticides
- Used as an extractant solvent in manufacture of rubber, essential oils, sterols and alkaloids, guttapercha, resins, and in the recovery of fat from waste products
- Used in chemical analysis and assays; and in photographic processing
- Used as a general solvent of lacquers plastics, dyes, fats, greases, gums, oils, adhesives, and waxes, and in the rubber cleaning and dry cleaning industries
- Prior use as an anesthetic has been discontinued and uses in human drugs and cosmetics are now limited to use as a process solvent for final products that contain only residual amounts of chloroform
- Used as a fumigant for soil, a mildewicide for tobacco seedlings, a grain fumigant for various stored dry grains, and as an insecticide
Methods that are effective in controlling worker exposures to chloroform, depending on the feasibility of implementation, are as follows:
- Process enclosure
- Local exhaust ventilation
- General dilution ventilation
- Personal protective equipment
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 chloroform 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 chloroform, 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 skin, liver, kidneys,
heart, and central nervous system.
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 chloroform 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 skin, liver, kidneys, heart, or central nervous
system.
* Periodic medical evaluations
Occupational health interviews and physical examinations
should be performed at regular intervals during the employment period, as
mandated by any applicable Federal, State, or local standard. Where no standard
exists and the hazard is minimal, evaluations should be conducted every 3 to 5
years or as frequently as recommended by an experienced occupational health
physician. Additional examinations may be necessary if a worker develops
symptoms attributable to chloroform exposure. The interviews, examinations, and
medical screening tests should focus on identifying the adverse effects of
chloroform on the skin, liver, kidneys, heart, or central nervous system.
Current health status should be compared with the baseline health status of the
individual worker or with expected values for a suitable reference population.
* Termination medical evaluations
The medical, environmental, and occupational history
interviews, the physical examination, and selected physiologic or laboratory
tests that were conducted at the time of placement should be repeated at the
time of job transfer or termination to determine the worker's medical status at
the end of his or her employment. Any changes in the worker's health status
should be compared with those expected for a suitable reference population.
Because occupational exposure to chloroform 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 presence of chloroform in the blood and in expired air is an
indication of exposure, but data are insufficient to correlate blood or breath
levels with indices of exposure. Therefore, no biological monitoring test
acceptable for routine use has yet been developed for chloroform.
WORKPLACE MONITORING AND MEASUREMENT
Determination of a worker's exposure to airborne
chloroform 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 (ceiling or
TWA) until a maximum collection volume of 10 liters is reached (TWA) or for a
minimum collection time of 15 minutes (ceiling). The sample is then treated
with 99:1 carbon disulfide:dimethylformamide. Analysis is conducted by gas
chromatography using a flame ionization detector (GC/FID). This method (OSHA 5)
is described in the OSHA Computerized Information System [OSHA 1994] and is
fully validated. NIOSH has published a similar method (Method No. 1003-for
halogenated hydrocarbons) that can also be used to determine a worker's
exposure to airborne chloroform [NIOSH 1994b
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