Omega 3 Contamination.

“Millions of people who take fish oil for health benefits have been kept in the dark about the levels of PCBs and other contaminants they may be swallowing with the omega-3s.”

http://www.veterinarypracticenews.com/vet-practice-news-columns/complementary-medicine/how-green-are-your-omega-3-supplements.aspx

http://superchiaseed.com/milas-omega-3s-take-a-quantum-leap-over-toxic-fish/