The chemical you're referring to is lufenuron, which has not been approved in Norway. In fact, the company withdrew its application to have it approved in Norway, so we are experimenting with it here. The fish are dangerous for human consumption for 350 days. That suggests that the chemical is being purged from the fish over that period of time. Therefore, you'd have to test the mucus, the urine and the feces coming out of these fish to know what it's doing to the waters outside.
This industry is in a constantly escalating drug war with sea lice, which turn out to be pretty remarkable little creatures. They are resistant to every drug that is applied to them, so we're just going to keep going with more and more drugs. We can only assume that they will become resistant to this drug as well because IntraFish, the global media outlet for the industy, calls sea lice a $1-billion problem for the salmon farming industry right now. Nobody is saying they have solved it.
Lufenuron is not going to solve it. We're experimenting with it in a UNESCO biosphere reserve, Clayoquot Sound, in first nations territory, in a place where wilderness tourism is a booming industry that relies on salmon.
I think that regulating salmon farms in the open ocean is mission impossible. Nobody has done it successfully worldwide.