Doomwatch (1972)

A scientist from the Doomwatch environmental group, Dr. Del Shaw, is sent to the island of Balfe to check on the aftereffects of an oil tanker that went down a year earlier. What he finds is that many residents are suffering from a disfiguring disease that also makes them violent. The residents are quite hostel as Del looks for answers.

Someone carrying a rifle is constantly monitoring his activities from afar. Eventually, Del checks out the oceanic Naval dumping ground at Castle Rock. It is on the opposite side of the island from the tanker mishap. A diver takes pictures of the submerged waste. There are the expected naval containers of low-level radioactive waste, but there is a host of other containers bearing a number code. These are traced to the Doran Chemical Company. The containers were illegally dumped by a contracted disposal company and filled with pituitary growth hormone that did not work as designed. Beached containers of this are releasing the contents where fish ingest it. When the fish are consumed by the islanders, the excess amounts of growth hormone cause acromegaly, a disease characterized by growth of bones in the hands and brow area. The islanders have to be convinced of this explanation. They were blaming it on too much inbreeding given the small gene pool among island folk.