Polychlorinated Biphenyls Environmental Exposures
Polychlorinated Biphenyls Environmental Exposures
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.[2,3]
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.[5,6] 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.[1,10] 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).
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.
Cancer Risk Estimates
Potential lifetime excess cancer risk (LECR) is an indicator of Canadians’ exposure to known or suspected carcinogens in the environment. When potential LECR is more than 1 per million in a single pathway, a more detailed risk assessment may be useful for confirming the need to reduce individual exposure. If measured levels of polychlorinated biphenyls in relevant exposure pathways (outdoor air, indoor air, indoor dust, drinking water, and food and beverages) decrease, the risk will also decrease.
Potential LECR is calculated by multiplying lifetime average daily intake (the amount inhaled or ingested) by a cancer potency factor or unit risk factor. More than one cancer potency factor may be available, because agencies interpret the underlying health studies differently, or use a more precautionary approach. Our results use cancer potency factors from Health Canada, the US Environmental Protection Agency (US EPA), and/or the California Office of Environmental Health Hazard Assessment (OEHHA).
The calculated lifetime daily intake and LECR results for polychlorinated biphenyls are provided in the tables below. For more information on supporting data and sources, click on the Methods and Data tab below.
Calculated Lifetime Daily Intake
Lifetime Excess Cancer Risk (per million people)
*LECR based on average intake x cancer potency factor from each agency
Compare substances: Canadian Potential Lifetime Excess Cancer Risk, 2011
The data in this table are based on average intake and Health Canada’s cancer potency factor, assuming no change in measured levels. When Health Canada values are not available, United States Environmental Protection Agency values are used.
Click the second tab to view LECR data.
**Exposure not applicable: For indicated pathways, substance not present, not carcinogenic, or exposure is negligible
**Gap in data: No cancer potency factor or unit risk factor, or no data available
IARC Group 1 = Carcinogenic to humans, IARC Group 2A = Probably carcinogenic to humans, IARC Group 2B = Possibly carcinogenic to humans
NOTE: Chromium (hexavalent) estimates assume that 5% of total chromium measured in outdoor air is hexavalent and 8% total chromium measured in indoor dust is hexavalent.
Potential LECR assumes exposure occurs at the same level, 24 hours per day, for 70 years. This is rarely true for any single individual, but using a standard set of assumptions allows us to provide a relative ranking for known and suspected carcinogens across different exposure routes. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
Methods and Data
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