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Chloroprene (2-Chloro-1,3-Butadiene)

 

CHLOROPRENE (2-CHLORO-1,3-BUTADIENE)

126-99-8 

Hazard Summary-Created in April 1992; Revised in January 2000

    Exposure to chloroprene is primarily occupational.  Symptoms reported from acute (short-term) human exposure to high concentrations of chloroprene include giddiness, headache, irritability, dizziness, insomnia, fatigue, respiratory irritation, cardiac palpitations, chest pains, nausea, gastrointestinal disorders, dermatitis, temporary hair loss, conjunctivitis, and corneal necrosis.  Symptoms of chronic (long-term) exposure in workers were fatigue, chest pains, giddiness, irritability, dermatitis, and hair loss.  Chronic occupational exposure to chloroprene vapor may contribute to liver function abnormalities, disorders of the cardiovascular system, and depression of the immune system.  A National Toxicology Program (NTP) study concluded that chloroprene showed clear evidence of carcinogenic activity in both rats and mice.  EPA has classified chloroprene as a Group D, not classifiable as to human carcinogenicity.  The International Agency for Research on Cancer (IARC) has classified chloroprene as a Group 2B, possibly carcinogenic to humans.

Please Note: The main sources of information for this fact sheet are EPA's Health and Environmental Effects Profile for Chloroprene and EPA's Summary Overview of Health Effects Associated with Chloroprene.

Uses

  • Chloroprene is polymerized to form polychloroprene (neoprene), a synthetic rubber used for wire and cable covers, gaskets, automotive parts, adhesives, caulks, flame-resistant cushioning and other applications requiring chemical, oil and weather resistance or high gum strength. (4,6)

Sources and Potential Exposure

  • Workers may be occupationally exposed to chloroprene by inhalation or dermal exposure. (1)
  • The release of chloroprene to the environment may occur during its manufacture, transport, and storage and during the manufacture of polychloroprene elastomers and polychloroprene-containing products. (2)

Assessing Personal Exposure

  • No information was located regarding the measurement of personal exposure to chloroprene.

Health Hazard Information

Acute Effects:
  • Symptoms reported from acute human exposure to high concentrations of chloroprene include giddiness, headache, irritability, dizziness, insomnia, fatigue, respiratory irritation, cardiac palpitations, chest pains, nausea, gastrointestinal disorders, dermatitis, temporary hair loss, conjunctivitis, and corneal necrosis. (2-4)
  • Acute exposure may damage the liver, kidneys, and lungs; affect the circulatory system and immune system; depress the central nervous system (CNS); irritate the skin and mucous membranes; and cause dermatitis and respiratory difficulties in humans. (2-4)
  • High level exposures have affected the liver, lungs, kidneys and CNS in animals exposed by inhalation, gavage, or injection.  Acute oral exposure of rats caused inflammation of the mucous membranes; damage to the lungs, liver, spleen, and kidneys; and irritation of the gastrointestinal tract. (4,5)
  • Acute animal tests in rats and mice, have demonstrated chloroprene to have moderate acute toxicity by inhalation and high acute toxicity from ingestion. (5)
Chronic Effects (Noncancer):
  • Symptoms of chronic exposure in workers were fatigue, chest pains, giddiness, irritability, dermatitis, and hair loss. (2)
  • One study has suggested that chronic exposure of humans to chloroprene vapor associated with neoprene production may contribute to liver function abnormalities. Disorders of the cardiovascular system and depression of the immune system have also been observed in workers chronically exposed to chloroprene. (2-4)
  • Eye irritation, nasal discharge, olfactory epithelial degeneration, restlessness, lethargy, hair loss, growth retardation, and effects to the liver, kidney, thyroid, blood, and lungs have been observed in rodents following chronic inhalation exposure. (4,6)
  • EPA has calculated a provisional Reference Concentration (RfC) of 0.007 milligrams per cubic meter (mg/m3) for chloroprene based on respiratory effects in rats. The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups), that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime. It is not a direct esimator of risk but rather a reference point to gauge the potential effects. At exposures increasingly greater than the RfC, the potential for adverse health effects increases. Lifetime exposure above the RfC does not imply that an adverse health effect would necessarily occur. The provisional RfC is a value that has had some form of Agency review, but it does not appear on IRIS. (7)
  • EPA has calculated a provisional Reference Dose (RfD) of 0.02 milligrams per kilogram body weight per day (mg/kg/d) for chloroprene. (7)
Reproductive/Developmental Effects:
  • A study reported functional disturbances in spermatogenesis in workers exposed to chloroprene and increased spontaneous abortions in the wives of exposed workers.  However, insufficient details are available in the reports to adequately evaluate the results. (2-4)
  • Reproductive effects including a decreased number of spermatogonia, a decline in sperm motility, an increased number of dead sperm, and degeneration of the testes have been observed in male rats exposed by inhalation or dermal contact. (2-4,9)
  • Increased embryonal mortality and decreased fetal weight were reported in rats exposed by inhalation; contamination may have occurred during this study.  No effects on embryonic or fetal survival nor incidence of soft tissue or skeletal defects were observed in other studies of rats exposed by inhalation. (2-4,6)
Cancer Risk:
  • Epidemiological studies of rubber workers in the Soviet Union have indicated a possible association between exposure to chloroprene and skin and lung cancer.  However, levels of exposure causing symptoms have not been well defined and these studies have major methodological deficiencies.  An increased incidence of lung cancer was not reported in another study of American workers occupationally exposed to chloroprene during the manufacture of neoprene. (2-4,6)
  • An inhalation bioassay by the NTP showed clear evidence of carcinogenic activity in both rats and mice, based on increased incidences of neoplasms of the oral cavity, thyroid gland, lung, kidney, liver, skin, mammary glands, and other organs. (9)
  • EPA has classified chloroprene as a Group D, not classifiable as to human carcinogenicity, because of the absence of adequate data.  EPA has stated that, due to the structural similarity of the compound to 1,3-butadiene and positive mutagenicity tests, unnecessary exposure should be avoided.  Newer human and animal studies are now available. (2,6)
  • The International Agency for Research on Cancer (IARC) has classified chloroprene as a Group 2B, possibly carcinogenic to humans. (13)

Physical Properties

  • The chemical formula for chloroprene is C4H5Cl, and its molecular weight is 88.54 g/mol. (4,6)
  • Chloroprene occurs as a colorless, mobile, flammable, and volatile liquid that is slightly soluble in water. (1,2,4,6)
  • Chloroprene has an ether-like odor, with an odor threshold of 15 parts per million (ppm) (55 mg/m3). (2,8)
  • The vapor pressure for chloroprene is 220 mm Hg at 25 °C, and its log octanol/water partition coefficient (log Kow) is 2.06. (6)


Conversion Factors:
To convert concentrations in air (at 25 °C) from ppm to mg/m3: mg/m3 = (ppm) × (molecular weight of the compound)/(24.45).  For chloroprene: 1 ppm = 3.62 mg/m3.

Health Data from Inhalation Exposure

ACGIH TLV--American Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.
LC50 (Lethal Concentration50)--A calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined
NIOSH IDLH--National Institute of Occupational Safety and Health's immediately dangerous to life or health limit; NIOSH recommended exposure limit to ensure that a worker can escape from an exposure condition that is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from the environment.
NIOSH REL ceiling--NIOSH's recommended exposure limit ceiling; the concentration should not be exceeded at any time.
OSHA PEL--Occupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained in December 1999.
a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.
b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.  OSHA numbers are regulatory, whereas NIOSH and ACGIH numbers are advisory.

References

  1. M. Sittig. Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed. Noyes Publications, Park Ridge, NJ. 1985.
  2. U.S. Environmental Protection Agency. A Summary Overview of Health Effects Associated with Chloroprene. EPA/600/8-85/011F. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1985.
  3. International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Some Monomers, Plastics and Synthetic Elastomers, and Acrolein. Volume 19. World Health Organization, Lyon. 1979.
  4. U.S. Environmental Protection Agency. Health and Environmental Effects Profile for 2-Chloro-1,3-Butadiene. EPA/600/x-84/112. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1984.
  5. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
  6. U.S. Environmental Protection Agency. Health and Environmental Effects Document for 2-Chloro-1,3-Butadiene (Chloroprene). ECAO-CIN-G037. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1989.
  7. U.S. Environmental Protection Agency. Health Effects Assessment Summary Tables.  FY 1997 Update.  Solid Waste and Emergency Response, Office of Emergency and Remedial Response,  Cincinnati, OH.  EPA/540/R-97-036.  1997.
  8. J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. U.S. Environmental Protection Agency. 1983.
  9. National Toxicology Program. Toxicology and Carcinogenesis Studies of Chloroprene (CAS No. 126-99-8) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). TR No. 467. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1998.
  10. American Conference of Governmental Industrial Hygienists (ACGIH). 1999 TLVs and BEIs.  Threshold Limit Values for Chemical Substances and Physical Agents.  Biological Exposure Indices. Cincinnati, OH.  1999.
  11. Occupational Safety and Health Administration (OSHA).  Occupational Safety and Health Standards, Toxic and Hazardous Substances. Code of Federal Regulations. 29 CFR 1910.1000.  1998.
  12. National Institute for Occupational Safety and Health (NIOSH).  Pocket Guide to Chemical Hazards. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention.  Cincinnati, OH.  1997.
  13. International Agency for Research on Cancer. IARC Monographs on the Evaluation of Carcinogenic Risk to Humans. Volume 71: Re-evaluation of Some Organic Chemicals, Hydrazine, and Hydrogen Peroxide. 1998.

 

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