July 31, 2003

PCBs in Farmed Salmon: Farmed salmon & cancer

Farmed salmon and cancer

To better understand the health impacts of PCBs in farmed salmon, the Environmental Working Group conducted the first-ever exposure and risk assessment of PCB contamination in farmed salmon. The analysis is based on published, peer-reviewed EPA conclusions on the toxicity and cancer potency of PCBs, and is made possible by state-of-the-art fish consumption data derived from 20,000 adults over the twelve-year period from 1990 through 2002. It assumes the farmed salmon is the only source of PCB exposure in the diet and that people are not exposed to any other pollutants that could exacerbate the cancer risks of PCBs.

The results of this analysis show:

  • About 23 million people eat salmon at least once a month. Roughly 1.3 million people eat salmon once a week. Based on these data we estimate that 800,000 people face an excess lifetime cancer risk of more than one in 10,000 from eating farmed salmon, and 10.4 million people face a cancer risk exceeding one in 100,000 - the allowable risk threshold the government has selected for PCBs in recreationally caught fish. The government's preferred risk threshold for contaminants like PCBs is one in 1,000,000, but in the case of PCBs high background levels in the environment force selection of a higher risk threshold.
  • PCB levels in farmed salmon would have to drop about 90 percent (to the levels found in wild salmon) to protect heavy salmon eaters (two meals per week), from unsafe exposures to PCBs.

Table. Millions of adults face an excessive cancer risk from PCBs in farmed salmon.

Number of adults facing unacceptably high cancer risk from eating farmed salmon

Excess lifetime cancer risk from PCBs in farmed salmon



> 1 in 1,000


> 1 in 10,000


> 1 in 100,000


> 1 in 1,000,000


Federal limit for acceptable upperbound cancer risk from a chemical contaminant

1 in 1,000,000

Source: Exposure and risk analysis conducted by EWG, based on data from Axys (2003).