Levels of PCBs in different foods:
- Animal fat: 20 to 240 μg/kg
- Cow's milk: 5 to 200 μg/kg
- Butter: 30 to 80 μg/kg
- Fish: 10 to 500 μg/kg, on a fat basis. Certain fish species (eel) and fish products (fish liver and fish oils) may contain much higher levels, up to 10 mg PCBs/kg
- Vegetables, cereals, fruits, and a number of other products: <10 μg/kg
PCBs as well as other POPs (Persistent Organic Pollutants, including many pesticides) are fat soluble and accumulate in the fat and milk of animals. They also bioaccumulate, becoming more concentrated in animal tissue as you move up the food chain.
* Tuna is a large fish. Paul Greenberg: "Tuna Are Something Bigger Than The Space They Occupy"