Polychlorinated biphenyls (PCBs) are a group of chemicals made up of 209 isomers. Synthetic compounds, they are similar in structure but vary considerably in their physical properties.[2,3] PCBs may be oily liquids or solids that are colourless to white, depending on the exact chemical make-up. They are very stable and persist in the environment. Polychlorinated biphenyls may also be referred to as chlorobiphenyls, chlorinated biphenyls or Aroclor, a commercial name. There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.
PCBs as a group have been classified by the International Agency for Research on Cancer (IARC) as Group 1, carcinogenic to humans. This classification is based on consistent associations between PCB exposure and increased risk of melanoma in humans. There is also limited evidence from some studies suggesting that exposure is linked to increased risks of non-Hodgkin lymphoma and breast cancer. The first PCB classified by IARC was 3,3',4,4',5-pentachlorobiphenyl (PCB-126); it was classified in 2012 as Group 1, based on strong mechanistic evidence for genotoxicity.
PCB exposure may irritate the skin and at high levels can cause liver damage. Stored in fatty tissues, PCBs can build up to concentrations far exceeding those found in the environment. Little is known about the long-term health impacts of exposure to PCBs, since most observed health effects have resulted from short-term and high-level accidental or occupational exposures.
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
All exposure limits are defined in the legislation as chlorodiphenyl except for Ontario that defines the limit as polychlorinated biphenyls.
Canadian Environmental Guidelines
Canadian Drinking Water Guidelines
Ontario Drinking Water Standards
IMAC = 0.003 µg/L
Ontario Ambient Air Quality Criteria
24 hour: 0.15 µg/m3
Annual: 0.035 µg/m3
BC's Contaminated Sites Regulation, BC Reg 375/96
For the protection of human health, sets soil standards for:
Agricultural, urban park, residential soil: 5 μg/g
Commercial soil: 15 μg/g
Industrial soil: 50 μg/g
Agreement Respecting the Great Lakes Basin Ecosystem
Concentration in fish tissues should not exceed 0.1 μg/g for the protection of birds and animals which consume fish
µg/L = micrograms per litre
µg/m3 = micrograms per cubic meter
µg/g = micrograms per gram
IMAC = interim maximum allowable concentration
* Health Canada defines archived parameter as "parameters which are no longer found in Canadian drinking water supplies at levels that could pose a risk to human health, including pesticides which are no longer registered for use in Canada, and for mixtures of contaminants that are addressed individually."
Polychlorinated biphenyls were not included in other Canadian environmental guidelines reviewed.[14,15,16,17,18]
National Classification System for Contaminated Sites
Rank = "High hazard"
DSL = domestic substance list
CEPA = Canadian Environmental Protection Act
Polychlorinated biphenyls were not included in other Canadian government chemical listings reviewed.
The stable, relatively fire-resistant, and non-corrosive properties of PCBs have made them useful in a wide range of applications. Historically, PCBs were used extensively to make industrial materials such as sealing and caulking compounds, cutting oils, inks, and paint additives. They were also used to produce coolants and lubricants for certain kinds of electrical equipment, such as transformers and capacitors.
Historically in Canada, PCBs were widely used to manufacture electrical equipment, heat exchangers, hydraulic systems, and several other specialized applications.
According to Canadian legislation from 1980 and 1985, the only permissible use of PCBs is in older equipment, such as refrigerators, until the end of that equipment's service life.[25,26] The maximum allowable concentration of PCBs per equipment is 50 parts per million by weight. The equipment must have been designed to use PCBs at the time that it was imported, manufactured or knowingly offered for sale.
There was a 72% decrease in the amount of PCBs used or stored in Canada from 2012 to 2014. In 2014, 111 tonnes of PCBs were stored, 51 tonnes were in use, and 716 tonnes were destroyed.
Canadian Production and Trade
Canada has never manufactured PCBs, but imported approximately 40,000 tonnes annually from 1929 until the 1970s.
In 2002, the Canadian Working Group, Great Lakes Binational Toxics Strategy, classified three major industry sectors that needed to be targeted for PCB destruction, due to high levels of PCB storage. They include provincial and municipal governments, iron and steel manufacture, and forestry, pulp, and paper industries.[28,29]
In 2008, legislative efforts concentrated on preventing further production of PCBs, contamination of the environment, and destruction of currently stored PCBs. Standardized waste management procedures have been developed and many companies specialize in PCB disposal.
Production and Trade
72 kg of 'mixtures and preparations containing polychlorinated biphenyls PCBs, PCTs or PBBs'
0 kg of 'mixtures and preparations containing polychlorinated biphenyls PCBs, PCTs and PBBs'
kg = kilogram
PCT = polycyclohexylenedimethylene terephthalate
PBB = polybrominated biphenyls
Inhalation, dermal absorption and ingestion are all potential routes of occupational exposure to PCBs.
CAREX Canada estimates that approximately 8,100 Canadians are exposed to polychlorinated biphenyls in their workplaces. The largest industrial groups exposed are specialty trade contractors (e.g. electricians) in construction and electric power generation, transmission, and distribution industries. Other important industries exposed to PCBs are transportation equipment manufacturing, mining, and oil and gas extraction.
The largest occupational groups exposed to PCBs include industrial electricians, electrical power line and cable workers, contractors and supervisors in electrical and telecommunication trades, electrical mechanics, and electricians. Other occupational exposures may occur in workers involved in waste storage and incineration, and contaminated site remediation.[4,24] Welders and general maintenance workers in various industries may also encounter PCBs in old industrial paints and coatings. Exposure may also occur during accidental spills or fires involving equipment containing PCBs.[2,8]
Inhalation, dermal contact, and ingestion are potential routes of exposure to PCBs for the general population. All Canadians have PCBs in their bodies due to exposure to small amounts present in food, air, soil, and water. The greatest source of PCB exposure for Canadians is consuming contaminated foods.[24,33]
Due to PCBs' persistence and bioaccumulation potential, the highest concentrations are found in animals at the top of the food chain. Foods found to contain high concentrations of PCBs include fish (particularly sport fish caught in contaminated lakes or rivers), meat, and poultry. A survey on PCB concentrations in food, conducted in Vancouver in 2002, found that freshwater fish and marine fish carried the highest concentrations of PCBs.[34,35] A 2004 Canadian study of farmed fish found higher PCB levels in farmed versus wild salmon; however, the contaminant levels in farmed fish were still less than 1/80th of the acceptable level established by Health Canada.
According to Health Canada, the average daily dietary intake of PCBs is estimated to be less than ½ a millionth of a gram. Individuals who consume large amounts of fish, wildlife, or marine mammals may be exposed to higher concentrations. Infants may also be exposed to PCBs through breast milk. A study looking at over 300 breast milk samples collected between 1992 and 2005 across Canada found that median levels of PCBs declined significantly between 2002-2005. This was at the lower end of the concentration range reported in industrialized nations. CAREX Canada estimates that PCB levels in food and beverages result in an increased risk of cancer in Canada (very low data quality).
PCBs have been found in runoff, sediment, soil, rivers, creek water, lakes, leachate, pond effluents, landfills, and an underground oil-water layer.[2,39] There are no known natural sources of PCBs in the environment: the widespread prevalence of PCBs in the environment is due to prior industrial use and their environmental persistence. A 2007 study investigated PCB levels in Ontario rain, snow and surface waters. All samples were positive for PCBs. Concentrations varied between urban and rural areas; greater concentrations were found in urban areas. However, PCBs are still found in remote areas of Canada due to long-range transport by global air currents. Currently, there is insufficient measured data for CAREX Canada to produce environmental exposure estimates for PCBs in drinking water (data gap).
CAREX Canada estimates that PCB levels in outdoor air is negligible, however, PCB levels in indoor air result in an increased risk of cancer (data quality very low). In addition, we estimate that PCB levels in indoor dust do not result in an increased risk of cancer (data quality very low).
For more information, see CAREX Canada's environmental exposure estimates for polychlorinated biphenyls. PCB release is not reportable to the National Pollutant Release Inventory in Canada. No household products containing PCBs were listed in the Household Products Database from the United States.
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to polychlorinated biphenyls in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at email@example.com.