Carbon Tetrachloride

Carbon tetrachloride is an inorganic compound with the formula CCl4.[fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1] It is a clear liquid with a sweet odour that evaporates very easily. Carbon tetrachloride does not easily burn and is almost insoluble in water. It is a manufactured chemical and does not occur naturally in the environment.[2,3]

 

Uses [2]

 

Carbon tetrachloride has been produced in large quantities to make refrigeration fluid and propellants for aerosol cans. Since many refrigerants and aerosol propellants have been found to affect the earth’s ozone layer, the production of these chemicals is being phased out. Consequently, the manufacture and use of carbon tetrachloride has declined a great deal. In the past, carbon tetrachloride was widely used as a cleaning fluid (in industry and dry cleaning establishments as a degreasing agent, and in households as a spot remover for clothing, furniture, and carpeting). Carbon tetrachloride was also used in fire extinguishers and as a fumigant to kill insects in grain. Most of these uses were discontinued in the mid-1960s. Until recently, carbon tetrachloride was used as a pesticide, but this was stopped in 1986.

 

In the Environment [2]

 

As carbon tetrachloride evaporates easily, most of the compound released to the environment during its production and use reaches the air, where it is found mainly as a gas. It can remain in air for several years before it is broken down to other chemicals. Small amounts of carbon tetrachloride are found in surface water. Because it evaporates easily, much of it will move from surface water to the air within a few days or weeks. However, it may be trapped in groundwater for longer periods. Carbon tetrachloride is not expected to stick to soil particles. If spilled onto the ground, much of it will evaporate to the air. Some of it may also go into groundwater, where it can remain for months before it is broken down to other chemicals. It is not expected to build up in fish. It is unknown whether it builds up in plants.

 

Sources and Routes of Exposure [4]

 

Sources of Exposure

 

General Populations

 

  • Carbon tetrachloride is found in air, water and soil. Inhalation of contaminated air and ingestion of contaminated drinking water are the primary routes of exposure.
  • The general public is not likely to be exposed to large amounts of carbon tetrachloride. Populations living close to waste sites or areas of heavy carbon tetrachloride use may have increased risk of exposure.
  • Exposure may occur through volatisation of carbon tetrachloride from tap water during showering, bathing or cooking.
  • Carbon tetrachloride is currently banned from use in commercial products.

 

Occupational Populations

 

  • Inhalation of contaminated air is the primary route of exposure in occupational settings.
  • Workers involved in the manufacture of carbon tetrachloride are most likely to be exposed than the general public.

 

Routes of Exposure

 

  • Inhalation – Predominant route of exposure for general population.
  • Oral – Major route of exposure for the general population through ingestion of contaminated drinking water.
  • Dermal – Minor route of exposure through dermal contact with contaminated soil.

 

Health Effects [3]

 

Acute Effects

 

  • Acute inhalation and oral exposures to high levels of carbon tetrachloride have been observed primarily to damage the liver (swollen, tender liver, changes in enzyme levels, and jaundice) and kidneys (nephritis, nephrosis, proteinurea) of humans. Depression of the central nervous system has also been reported. Symptoms of acute exposure in humans include headache, weakness, lethargy, nausea, and vomiting.
  • Delayed pulmonary oedema (fluid in lungs) has been observed in humans exposed to high levels of carbon tetrachloride by inhalation and ingestion, but this is believed to be due to injury to the kidney rather than direct action of carbon tetrachloride on the lung.
  • Acute animal exposure tests in rats, mice, rabbits, and guinea pigs have demonstrated carbon tetrachloride to have low toxicity from inhalation exposure, low-to-moderate toxicity from ingestion, and moderate toxicity from dermal exposure.

 

Chronic Effects (Noncancer)

 

  • Chronic inhalation or oral exposure to carbon tetrachloride produces liver and kidney damage in humans and animals.
  • EPA has not established a Reference Concentration (RfC) for carbon tetrachloride.
  • The California Environmental Protection Agency (CalEPA) has established a chronic reference exposure level of 0.04 milligrams per cubic metre (mg/m3) for carbon tetrachloride based on liver effects in guinea pigs.
  • ATSDR has established an acute duration (1-14 days) inhalation minimal risk level (MRL) of 1.3 mg/m3 (0.2 parts per million [ppm]) based on liver effects in rats, and an intermediate duration (14-365 days) MRL of 0.3 mg/m3 (0.05 ppm) also based on liver effects in rats.
  • The Reference Dose (RfD) for carbon tetrachloride is 0.0007 milligrams per kilogram per day (mg/kg/d) based on the occurrence of liver lesions in rats.

 

Reproductive/Developmental Effects

 

  • No information is available on the reproductive effects of carbon tetrachloride in humans. Limited epidemiological data have indicated a possible association between certain birth outcomes (e.g., birth weight, cleft palate) and drinking water exposure. However, as the water contained multiple chemicals, the role of carbon tetrachloride is unclear.
  • Decreased fertility and degenerative changes in the testes have been observed in animals exposed to carbon tetrachloride by inhalation.
  • Birth defects have not been observed in animals exposed to carbon tetrachloride by inhalation or ingestion.

 

Cancer Risk

 

  • Occasional reports have noted the occurrence of liver cancer in workers who had been exposed to carbon tetrachloride by inhalation exposure; however, the data are not sufficient to establish a cause-and-effect relationship.
  • Liver tumours have developed in rats and mice exposed to carbon tetrachloride by gavage (experimentally placing the chemical in their stomachs).
  • EPA has classified carbon tetrachloride as a Group B2, probable human carcinogen.

 

Safety [5]

 

First Aid Measures

 

  • Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Do not use an eye ointment. Seek medical attention.
  • Skin Contact: After contact with skin, wash immediately with plenty of water. Gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. Cover the irritated skin with an emollient. If irritation persists, seek medical attention. Wash contaminated clothing before reusing.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek medical attention.
  • Inhalation: Allow the victim to rest in a well-ventilated area. Seek immediate medical attention.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention.
  • Ingestion: Do not induce vomiting. Loosen tight clothing such as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention.

 

Exposure Controls & Personal Protection

 

Engineering Controls

 

  • Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapours below their respective threshold limit value.
  • Ensure that eyewash stations and safety showers are proximal to the workstation location.

 

Personal Protective Equipment

 

The following personal protective equipment is recommended when handling carbon tetrachloride:

  • Splash goggles;
  • Lab coat;
  • Vapour respirator (Be sure to use an approved/certified respirator or equivalent);
  • Gloves

 

Personal Protection in Case of a Large Spill:

  • Splash goggles;
  • Full suit;
  • Vapour respirator;
  • Boots;
  • Gloves;
  • A self-contained breathing apparatus should be used to avoid inhalation of the product.
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

 

Regulation

 

United States [6]

 

EPA: The Environmental Protection Agency has set a limit for carbon tetrachloride in drinking water of 5 parts of carbon tetrachloride per billion parts of water (5 ppb). The EPA has also set limits on how much carbon tetrachloride can be released from an industrial plant into waste water and is preparing to set limits on how much carbon tetrachloride can escape from an industrial plant into outside air.

 

OSHA: The United State Occupational Safety & Health Administration has set the following Permissible Exposure Limits (PEL):

  • General Industry: 29 CFR 1910.1000 Z-2 Table — 10 ppm TWA; 25 ppm Ceiling for 5 minutes in any 3 hours; 200 ppm Peak
  • Construction Industry: 29 CFR 1926.55 Appendix A — 10 ppm, 65 mg/m3 TWA; Skin
  • Maritime: 29 CFR 1915.1000 Table Z-Shipyards — 10 ppm, 65 mg/m3 TWA; Skin

 

ACGIH: The American Conference of Governmental Industrial Hygienists has set a Threshold Limit Value (TLV) for carbon tetrachloride is 5 ppm, 31 mg/m3 TWA; 10 ppm, 63 mg/m3 STEL; Skin; Appendix A2 – Suspected Human Carcinogen

 

NIOSH: The National Institute for Occupational Safety and Health has established a Recommended Exposure Limit (REL) for carbon tetrachloride of 2 ppm, 12.6 mg/m3 STEL (60 Minutes); Appendix A – NIOSH Potential Occupational Carcinogens

 

Australia [7]

 

Safe Work Australia: Safe Work Australia has established a Time Weighted Average Concentration (TWA) for carbon tetrachloride of 0.1ppm/ 0.63mg/m3 for a 40-hour workweek.

References

 

  1. http://en.wikipedia.org/wiki/Carbon_tetrachloride
  2. http://www.atsdr.cdc.gov/phs/phs.asp?id=194&tid=35
  3. http://www.epa.gov/ttn/atw/hlthef/carbonte.html
  4. http://www.atsdr.cdc.gov/toxguides/toxguide-30.pdf
  5. http://www.sciencelab.com/msds.php?msdsId=9927342
  6. http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=195&tid=35
  7. http://www.safeworkaustralia.gov.au/sites/swa/about/Publications/Documents/772/Workplace-exposure-standards-for-airborne-contaminants.docx

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