In a letter sent in response to questions from Rep. Edward J. Markey (D-Mass.), the agency responsible for ensuring the safety of seafood said that chemicals used to break up the slicks are not as dangerous to human health as the oil itself. FDA scientists do not believe that the chemicals accumulate significantly in the tissue of fish and shellfish, and so, even if the fish absorb the chemicals through gills or other ways, the fish do not retain them, Jeanne Ireland, FDA's assistant commissioner for legislation, wrote to Markey. That means they do not pass up the food chain...