As early as 2004, scientists found levels of polychlorinated biphenyls, a probable carcinogen known as PCBs, seven times higher in farmed Atlantic salmon than in wild salmon. More recent studies found high levels of other chemicals and antibiotics in farmed salmon. Researchers at Arizona State University discovered increases in drug-resistant antibiotics in farmed seafood over the past 30 years, leading to concerns about increased risk of antibiotic resistance in humans. Toxins often wind up in salmon flesh and accumulate in people who eat the fish.

https://time.com/6199237/is-farmed-salmon-healthy-sustainable/?