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CAS No. 67-66-3

Photo: Wikimedia Commons^[1]

IARC Monograph Vol. 73, 1999 (Group 2B)

General Information

Chloroform is a colourless, volatile liquid with an ethereal odour^[2], which is one of a group of compounds found as by-products of chlorination of drinking water, known as trihalomethanes. It may also be referred to as trichloromethane or methane trichloride.^[3] There are numerous other synonyms and product names; see HSDB for more information.^[4]

In 1999, IARC classified chloroform as Group 2B, possibly carcinogenic to humans, based on evidence in experimental animals.^[3] Chloroform is a liver and kidney carcinogen in mice and rats.^[3] Several epidemiological studies have suggested that exposure to chloroform in chlorinated drinking water is associated with excess cancers, particularly of the urinary bladder, colon and rectum.^[3] Causality, however, can not be determined because of uncertainties, including confounding by other chlorination by-products.^[3]

Additionally, chronic inhalation exposure to elevated levels of chloroform may cause damage to liver, kidney, as well as neurological symptoms.^[5] Acute inhalation exposure to chloroform can cause dizziness, fatigue, and headache.^[5] Dermal contact can cause irritation and damage to the skin.^[6]

Chloroform has been ranked by CAREX Canada for both the occupational and environmental settings as Group A (immediate high priority). 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	10
BC	2 [rt]
AB, MB, ON, NL, PE, NB, NS, YT	10
SK	ALARA
QC	5
NT, NU	10 50 [stel]
Other Jurisdiction	OEL (ppm)
ACGIH 2011 TLV	10

STEL = short term exposure limit

rt = reproductive toxin

ppm = parts per million

ALARC = As low as reasonably achievable

Canadian Environmental Guidelines

Jurisdiction	Limit	Year
Canadian Drinking Water Guidelines	For total trihalomethanes (THMs): 0.1 mg/L (MAC)	2010^[7]
Cosmetic Hotlist	Nor permitted	2011^[8]

MAC = Maximum Acceptable Concentration

Chloroform was not included in other Canadian government environmental guidelines reviewed.^[8,18]

Canadian Agencies/Organizations

Agency	Designation/Position	Year
Health Canada	DSL – low priority substance (already risk managed)	2006^[10]
CEPA	Priority Substance List*	2011^[11]

*A 2001 assessment of chloroform concluded that the criteria for inclusion as 'toxic' under paragraph 64(b) of CEPA 1999 was not met and further measures would not be pursued.^[11]

Chloroform was not included in other Canadian government chemical listings reviewed.^[13]

Main Uses

Prior to World War II, chloroform was used as an anaesthetic and in pharmaceutical preparations.^[5] Other historical uses include the production of resins, fats, greases, gums, waxes, and oils, and as a chemical intermediate in dye and pesticide production.^[11]

In more recent years, chloroform has been used predominately for the synthesis of other chemicals, such as hydroclorofluorocarbon-22 (HCFC-22) which is used as a refrigerant.^[5] It is also used in the extraction and purification of some antibiotics, alkaloids, vitamins, and flavours, and as a solvent for lacquers, floor polishes, and adhesives.^[2] Chloroform may be used as a fumigant for stored grain crops^[2], but it is not registered for this use in Canada.^[12]

Canadian Production and Trade

In 1995 there were 19 countries producing chloroform world wide.^[13] The US, EU and Japan are the main manufacturers of chloroform with a total global capacity of approximately 520,000 tonnes per year in the late 1990s.^[14]

Production and Trade

Activity	Quantity	Year
Canadian Production	None	1995^[15]
Domestic Consumption	300 t	1995^[15]
Export: Mainly to Dominican Republic	2 t of ‘chloroform (trichloromethane)’	2010^[16]
Import: From US	28 t of 'chloroform (trichloromethane)'	2010^[16]

t = tonne

Occupational Exposures

Inhalation and dermal exposure are the most important route of occupational exposure.^[5] Occupational exposure to chloroform may occur during its production and use as a solvent and chemical intermediate.^[3]

The main occupations exposed include workers involved in the manufacture and transportation of chloroform, the manufacture of fluorocarbons, as well as those exposed occupationally via its use as an extractant solvent, an element in chemical analysis and photographic processing, a general solvent, and as a fumigant, mildewicide, and insecticide.^[21] For other potential occupational exposures, please see our Occupational Exposure Estimates for chloroform.

Environmental Exposures

The primary source of environmental exposure is ingestion of chloroform via chlorinated drinking water.^[2] Chloroform is produced during drinking water treatment by the reaction between chlorine and decomposing organic material.^[13] Typical concentrations of chloroform in Canadian chlorinated water range from 10 to 90 µg/litre (or parts per billion, ppb).^[11,13] Chlorinated water can also release aerated chloroform (i.e. during showering), creating an inhalation risk.^[2] Dermal absorption of chloroform from water can also occur.^[2] Once present, chloroform may persist in ground water for many years,^[5] but it does not bioaccumulate in aquatic animals.^[13] CAREX Canada is reviewing Canadian exposure to chlorination by-products as a group; please see the Carcinogen Profile for more information.

Chloroform is also found in ambient air and at low levels in some foods (such as milk and butter).^[3] Most chloroform in the environment is released by industrial sources, including pulp and paper mills, municipal wastewater treatment plants, chemical manufacturing plants and waste incinerators.^[11]

Although chloroform is not produced in Canada, it enters the environment through industrial releases and long range atmospheric transport from other non-Canadian cities.^[11] Chloroform has been detected in Canadian air, surface water and groundwater samples.^[19] From 1989 to 1996, chloroform was detected in approximately 69% of 8,807 24-h samples of indoor air collected across Canada.^[20] Concentrations were higher at urban sites and immediately adjacent to major roadways.^[20] Comparison between two time periods (1989-1992 and 1993-1996) found that chloroform concentrations were slightly lower in the more recent period.^[20] In 2001, it was estimated that the average Canadian daily exposure to chloroform was between 0.6 and 10.3 µg/kg-bw per day; the highest exposure based on body weight was calculated for infants who were formula fed.^[11]

Searches of environmental and consumer product databases yielded the following results on current potential for exposure to chloroform in Canada:

NPRI and US Household Products Database

NPRI 2009^[21]
Search term: 'chloroform'
Category	Quantity	Industry
Released into Environment	36 t	Pulp & paper mills and chemical manufacturers (13 companies)
Disposed of	46 t
Sent to off-site recycling	3.3 t