PARTICULARLY SENSITIVE SEA AREAS (PSSA) AND AREA TO BE AVOIDED (ATBA) To avoid risk of pollution and damage to the environment, entry into the IMO-adopted PSSA is affected by numerous restrictions and prohibitions. All vessels carrying oil or hazardous material, or any vessels exceeding 500GT, should avoid the IMO-adopted ATBA. For further details, see ADMIRALTY Sailing Directions or consult local authorities.