Large numbers of seabirds were killed by both acute and chronic oil pollution in the waters around the Northern Isles of Scotland in 1979. These mortalities closely coincided with the opening of the Sullom Voe Terminal in Shetland, the largest of Britain's North Sea oil-ports, and appeared to stem largely from the illegal discharge of ballast water or tank slops from tankers trading to Sullom Voe. By the middle of 1979, the seabird deaths around Orkney and Shetland had accounted for 85% of the British total of that year.

Public and political concern at these events forced the introduction of a number of non-statutory measures designed to eliminate or reduce chronic pollution offshore. In rapid and novel fashion the local authority and oil industry between them achieved a far greater degree of control than formerly over tanker traffic—through the introduction of such schemes as tanker routing, ‘areas of avoidance’, unscheduled aerial surveillance of all tankers, rigorous inspection of ballast quality and quantity, and the introduction through chartering contracts of the necessity for vessels to carry at least 35% ballast on arrival at the port (so providing a strong disincentive to deballast at sea).

Since the introduction of these measures, pollution, in the form of oil and oiled birds coming ashore, has decreased dramatically, and is now at a level which is tolerable, considering the scale of oil-related developments in and around Orkney and Shetland.