CAREX Canada

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CAS No. 1336-36-3

Photo: Wikimedia Commons^[1]

IARC Monograph Vol. 69, 1997 (Group 2A)

IARC Monograph Vol. 100F, 2012 (Group 1)

General Information

Polychlorinated biphenyls (PCBs) are a group of chemicals made up of 209 isomers.^[2] They are synthetic compounds that are similar in structure,^[3] but vary considerably by their physical properties.^[2] PCBs may be oily liquids or solids that are colourless to white, depending on the exact chemical make-up.^[2] They are very stable and persistent in the environment.^[4] Polychlorinated biphenyls may also be referred to as ‘chlorobiphenyls’, ‘chlorinated biphenyls’ or ‘Arochlor’, a commercial name.^[5] There are numerous other synonyms and product names; see HSDB for more information.^[5]

With one exception, PCBs as a group have been classified by IARC as Group 2A, possibly carcinogenic to humans.^[6,14] In animal studies with rats and mice, exposures to different PCBs were associated with malignant and/or benign tumours of the liver, spleen, thymus, gastrointestinal tract, thyroid, lung, mouth, uterus, and pancreas.^[2,6] Not all PCB congeners were carcinogenic in experimental animals.^[2] Epidemiological studies found increased incidence of liver, bile-duct and skin (melanoma) in people exposed to PCBs, but the results were inconsistence or confounded with other exposures.^[2,6] PCB exposure was also linked in some studies to increases in cancer at other tissue sites, such as brain, testes, lymphohemotopoietic tissues, gastrointestinal tract, and breast; however, not all studies found consistent increased risks and some studies had a limited number of subjects.^[2]

2,4,5,3’,4’-Pentachlorobiphenyl (PCB-126) has been classified by IARC as Group 1, carcinogenic to humans, based on strong mechanistic evidence for genotoxicity.^[14].

Other health effects of PCB exposure may include skin irritation and liver damage following high levels of exposure.^[7] PCBs are stored in fatty tissues and can build up to concentrations far exceeding those found in the environment.^[7] Little is known about the long-term health impacts of exposure to PCBs, since most observed health effects have resulted from short-term, high-level accidental or occupational exposures.^[3]

PCBs have been ranked by CAREX Canada as Group A (immediate high priority) for both the 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 (mg/m³)
Canada Labour Code	1 [45% Cl, sk] 0.5 [54% Cl, sk]
BC, AB, MB, NL, PE, NB, NS	1 [42% Cl, sk] 0.5 [54% Cl, sk]
SK	1 [42% Cl, sk] 3 [42% stel] 0.5 [54% Cl, sk] 1.5 [54% stel]
ON	0.05
NT, NU, YT	1 [42% Cl, sk] 2 [42% stel] 0.5 [54% Cl, sk] 1 [54% stel]
Other Jurisdiction	OEL (mg/m³)
ACGIH 2011 TLV	1 [42% Cl, sk] 0.5 [54% Cl, sk]

mg/m³ = milligrams per cubic meter

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

sk = easily absorbed through the skin

em = exposure must be reduced to the minimum

Cl = chlorine

Canadian Environmental Guidelines

Jurisdiction	Limit	Year
Canadian Drinking Water Guidelines	Archived	2010^[8]

Polychlorinated biphenyls were not included in other Canadian government environmental guidelines reviewed.^[9,19,20]

Canadian Agencies/Organizations

Agency	Designation/Position	Year
Health Canada	DSL – low priority substance (previously assessed/risk managed)	2006^[10]
CEPA	Schedule 1, paragraphs ‘a’, ‘b’, and ‘c’ (human health)	1999^[11]

Polychlorinated biphenyls were not included in other Canadian government chemical listings reviewed.^[13]

Main Uses

PCBs’ stable, relatively fire-resistant, and non-corrosive nature have made them useful in a wide range of applications.^[12] Historically, PCBs were used extensively to make industrial materials such as sealing and caulking compounds, cutting oils, inks and paint additives.^[15] They were also used in the production of coolants and lubricants for certain kinds of electrical equipment, such as transformers and capacitors.^[15]

Historically in Canada, PCBs were widely used for the manufacture of electrical equipment, heat exchangers, hydraulic systems, and several other specialized applications.^[16] In 1985, a Canadian inventory recorded 24,300 tonnes of PCBs in storage or used in electrical equipment.^[12]

According to Canadian legislation in 1980 and 1985 the only permissible use of PCBs is in older equipment, e.g. refrigerators, until the end of that equipment’s service life.^[16,17] The maximum allowable concentration of PCBs per equipment is 50 parts per million by weight.^[17] The equipment must have been designed to use PCBs at the time that it was imported, manufactured or knowingly offered for sale.^[17]

In 2005, the National Inventory of PCBs in use and PCB Wastes in Storage in Canada reported 1,615 PCB storage sites holding 106,369 tonnes of PCBs across Canada. The largest storage capacities were found in Ontario, BC and Nova Scotia.^[18] 8,095 tonnes of PCBs were still in use at the time, and 112,496 tonnes were in waste storage.^[18]

Canadian Production and Trade

Canada has never manufactured PCBs, but has imported approximately 40,000 tonnes annually from 1929 until the 1970s.^[12]

In 2002, the Canadian Working Group, Great Lakes Bi-national Toxics Strategy, classified provincial and municipal governments, iron and steel manufacture, and forestry, pulp, and paper as three major industry sectors that needed to be targeted for PCB destruction, due to high levels of PCB storage.^[22,23]

The Annual Progress Report for the Great Lakes Bi-national Toxics Strategy states the following about PCBs in Ontario in 2007:^[23] 90.2% of 1993 baseline high-level PCB storage waste was destroyed; the number of storage sites decreased from 1,529 in 1993 to less than 400 in 2007; and the amount of PCBs still in use decreased from > 8000 tonnes in 1989 to < 3000 tonnes in 2006.

In 2008, legislative efforts were concentrated on preventing further production of PCBs, contamination of the environment, and the destruction of currently stored PCBs.^[17] Standardized waste management procedures have been developed^[24] and there are companies specializing in PCB disposal.^[25]

Production and Trade

Activity	Quantity	Year
Export: Mainly to US	64 t of ‘mixtures and preparations containing polychlorinated biphenyls PCBs’	2010^[21]
Import: Mainly from US	2 t of ‘mixtures and preparations containing polychlorinated biphenyls PCBs’	2010^[21]

t = tonne

Occupational Exposures

Inhalation, dermal absorption and ingestion are potential routes of occupational exposure.^[2]

Individuals occupationally exposed to PCBs are involved in waste site clean up activities, the transformer industry, non-cellulose fiber industry, semiconductor and related industries, and in sawmills and planting mills.^[4] Further exposure may occur during disposal of PCB material, repair and maintenance of PCB transformers, accidents, fires or spills involving products containing PCBs.^[2,7]

In Canada, individuals servicing or replacing old electrical equipment, transporting PCBs to storage or destruction facilities, or working at such facilities are potentially exposed.^[15]

Environmental Exposures

Inhalation, dermal contact and ingestion are the primary routes of exposure to PCBs in the general population.^[2] All Canadians have PCBs in their bodies, due to exposure to small amounts present in food, air, soil and water.^[15]

PCBs have been found in runoff, sediment, soil, creek water, leachate, pond effluents, land fills and an underground oil-water layer.^[2,26] There are no known natural sources of PCBs in the environment:^[4] the widespread prevalence of PCBs in the environment is due to prior industrial use and their environmental persistence.^[2] Contamination found in Canada’s most remote areas is caused mainly by the long-range transport of PCBs by global air currents.^[15]

As with other countries, the oral consumption of contaminated foods is the Canadian population’s greatest source of exposure to PCBs.^[4]

PCBs are very persistent in living body tissue.^[16] Due to their bioaccumulation potential, the highest concentrations of PCBs are found in animals at the top of the food chain.^[15] Foods that have been found to contain high concentrations of PCBs include fish, meat and poultry, particularly sport fish caught in contaminated lakes or rivers.^[4] Infants may be exposed to PCBs through the ingestion of their mothers’ breast milk.^[4]

PCBs are included in Health Canada’s Total Diet Study Surveys.^[27] The latest survey on PCBs, conducted in Vancouver in 2002, found that fresh water fish and marine fish carried the highest concentrations of PCBs, at 7210 parts per trillion (ppt) and 4208 ppt, respectively.^[28]

According to Health Canada, the average daily dietary intake of PCBs is estimated to be less than ½ of a millionth of a gram.^[15] Individuals who consume large amounts of fish, wildlife or marine mammals may be exposed to higher concentrations.^[15]

In 2004, a Canadian study of farmed fish (Pew Study) found contaminant levels that were less than 1/80^th of the acceptable level established by Health Canada.^[29]

In 1996, a study of breast milk from Quebec women found mean concentrations of PCBs at 0.52 mg/kg lipids. This was at the lower end of the concentration range reported in industrialized nations.^[30]

Other sources of environmental exposure include hazardous waste sites, destruction of old electrical capacitors, old fluorescent lighting fixtures, electrical devices and appliances (e.g. television sets and refrigerators), fires in and/or explosion of electrical capacitors, and contaminated drinking water.^[4] PCBs continue to be released through spills and fires.^[16]

In 1991, the mean atmospheric concentrations of PCBs in two rural Ontario areas were 0.2 and 0.95 ng/m³.^[31]

In 2007, a study investigated PCB levels in Ontario rain, snow and surface waters.^[32] All samples were positive for PCBs. Total water concentrations ranged from 0.87 to 130 pg/L. Concentrations in snow and rain ranged from <1 to 100 pg/m² and from <1 to 44 pg/m²/day, respectively. Variation in concentration was noted between urban and rural areas, with greater concentrations in urban areas.

A joint research project by the University of Illinois at Chicago and the Canadian Environmental Law Association evaluated PCB concentrations in the Great Lakes. The project completed an inventory of PCBs in use and in waste storage in Canada. Refer to the project website for more information.^[33]

PCB release is not reportable to the National Pollutant Release Inventory (NPRI) in Canada.^[34] No household products containing PCBs were listed in the Household Products Database from the United States.^[35]

Sources

Other Resources

Published March 2012

Polychlorinated Biphenyls