Nasty chemical tributyltin, used to rid ship hulls of barnacles and algae, will be banned under an international treaty expected to be ratified within the next few days. TBT is cheap, effective, used on nearly all of the world’s 30,000 commercial vessels — and deemed by the U.S. EPA to be the most toxic chemical ever deliberately released into the world’s waters. And that’s saying something. The chemical has “profound reproductive effects” and kills off not only barnacles and algae, but other marine life. Says a representative of WWF, “It’s a tremendous victory for the marine environment.”