CAREX Canada

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CAS No. 56-23-5

Wikimedia Commons, Carbon tetrachloride^[1]

IARC Monograph Vol. 20, Suppl. 7, Vol. 71; 1999 (Group 2B)

General Information

Carbon tetrachloride (CCl₄) is a volatile, colourless liquid with a mild, sweet odour.^[2] Carbon tetrachloride may also be referred to as tetrachloromethane or carbon tet.^[6] There are numerous other synonyms and product names; see HSDB for more information.^[6]

Carbon tetrachloride has been classified by IARC as Group 2B, possibly carcinogenic to humans.^[3] Studies of workers exposed to CCl₄ suggest some association between exposure and an increased incidence of non-Hodgkin’s lymphoma. The strength of the association, however, was statistically weak and inconclusive.^[3] In animal studies, carbon tetrachloride caused liver, mammary gland and adrenal gland cancers in rats and mice.^[3]

Additionally, acute CCl₄ exposure can cause gastrointestinal and neurological symptoms such as nausea, dizziness, dyspnea, vomiting, as well as liver damage and death in severe cases.^[6]

Carbon tetrachloride has been ranked by CAREX Canada as Group B (possible high priority) for occupational and environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Canadian Jurisdictions	OEL (ppm)
Canada Labour Code	5 [sk] 10 [stel]
BC	2 [sk]
AB, MB, NL, NB, NS, PE	5 [sk] 10 [stel]
QC	5 [sk]
SK	ALARA
ON	2 [sk] 3 [stel]
YT	10 [sk] 20 [stel]
NU, NT	5 [sk] 20 [stel]
Other Jurisdictions	OEL (ppm)
ACGIH 2010 TLV	5 [sk] 10 [stel]

ppm = parts per million

sk = easily absorbed through the skin

stel = short term exposure limit (15 min. maximum)

ALARA = As Low As Reasonably Achievable

TLV = Threshold Limit Value (8 hour maximum)

Canadian Environmental Guidelines

Jurisdiction	Limit	Year
Canadian Drinking Water Guidelines	MAC 0.005 mg/L	2010^[11]
Health Canada Cosmetics Hotlist	Not Permitted	2010^[13]

MAC = Maximum Acceptable Concentration

Carbon tetrachloride was not included in other Canadian government environmental guidelines reviewed.^[12,14]

Canadian Agencies/Organizations

Agency	Designation/Position	Year
Health Canada	DSL – low priority substance; already risk managed	2006^[7]
CEPA	Schedule 1	2010^[10]

Main Uses

The major use of carbon tetrachloride was in the production of chlorofluorocarbon (CFCs), such as trichlorofluoromethane (Freon 11) and dichlorodifluoromethane (Freon 12), before CFCs were phased out due to their ozone depleting properties.^[3,5] CFCs were widely used as refrigerants, aerosol propellants and solvents.^[3]

CCl₄ was formerly used as a fumigant pesticide for grains.^[3] This use ceased in Canada in 1984.^[16] CCl₄ was also used as a solvent, in fire extinguishers, as a dry cleaning agent, and as a degreaser in both industrial and household settings.^[5]

In Canada, carbon tetrachloride is no longer produced or used to make any substance that causes ozone depletion. It is still allowed to be used as a feedstock for manufacturing other substances, however.^[17]

Canadian Production and Trade

Production and Trade

Activity	Quantity	Year
Export: N/A	None	2009^[8]
Import: Mainly from the US	91 t of ‘carbon tetrachloride’	2009^[8]

t = tonne

Occupational Exposures

Inhalation is the most important route of exposure to carbon tetrachloride.^[5]

In the past, high levels of occupational exposure occurred during the use of CCl₄ as a dry-cleaning agent and grain fumigant.^[4,5] Average and peak exposures during dry cleaning operations have been measured as high as 338 ppm and 7,100 ppm, respectively.^[4] Average CCl₄ concentrations reported in storage spaces with fumigated grain were mostly well below 5 ppm, but could reach as high as over 60 ppm.^[5]

Current occupational exposures may occur during the use of CCl₄ in chemical manufacturing processes and in research laboratories.^[3]

CAREX Canada is reviewing whether it is feasible to prepare exposure estimates for Canadian workers exposed to carbon tetrachloride. This will likely depend on availability of exposure data.

Environmental Exposures

Carbon tetrachloride does not occur naturally in the environment; therefore, CCl₄ present in the environment originates from anthropogenic releases.^[5,6] Releases mostly (73%) occur directly into the atmosphere.^[5] Due to its high volatility, nearly all environmental releases into other media, such as soil and water, end up in the air.^[5,17]

CCl₄ is a persistent chemical in air, with an average half-life of 30 to 100 years.^[8] Therefore, CCl₄ has been gradually accumulating in the environment over time^[4]; it is ubiquitous in outdoor and indoor air.^[17] A Canada-wide survey reported concentrations of CCl₄ ranged from 0.34-1.02 µg/m³ (0.60 µg/m³ average) in nearly 7,000 ambient air samples collected across 17 rural and 40 urban sites.^[17] Reported indoor concentrations were similar.

Public exposures are most likely to occur via inhalation of contaminated air and consumption of contaminated water.^[4,17] One survey of 48 homes in Windsor, Ontario found that the levels of CCl₄ in indoor air were higher in the summer (mean 0.72 µg/m³) compared to the winter (mean 0.60 µg/m³).^[17]

CCl₄ is also commonly detected in surface water, groundwater and drinking-water.^[3,5,17] Concentrations of CCl₄ in surface water in Canada are typically below 1 µg/L.^[17] Concentrations in water may be higher in groundwater systems where volatilization and degradation are limited, or if there are effluents from nearby waste or industrial sites.^[3,5,17]

CCl₄ has been found in effluents from a variety of industries, including metal manufacturing and finishing, foundries, paint and ink manufacturing, and petroleum refining.^[3] In addition to ingestion, inhalation and dermal exposures are also possible while using contaminated water for bathing and other purposes.^[5] Exposure may have occurred in the past via the use CCl₄-containing consumer products and the consumption of food fumigated with CCl₄.^[2] Because CCl₄ is no longer used in these applications in Canada, exposures via food and consumer products are expected to be unlikely.^[2,17]

Environment Canada’s National Pollutant Release Inventory (NPRI) reported the following release results for CCl₄ in Canada:

NPRI Reported Releases

NPRI 2009^[9]
Search Term:	’para-Dichlorobenzene'
Results:	3 companies

Category	Quantity	Industry
Released into Environment	0.006 t	Waste water treatment, plastic manufacture, metal manufacture
Disposed of	None
Sent to off-site recycling	None