This report is a contribution to the Strategic Environmental Assessment (SEA6) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). This report considers the major sources of contamination to the Irish Sea from offshore energy installations and puts them in the context of other sources of contamination to the region. The report also considers contamination of the wider environment, making use of data provided by monitoring programmes and other specific studies.

The oil and gas industry in the Irish Sea is small by comparison to that of the North Sea, but bears comparison to that of the Southern North Sea which is dominated by gas production and for which many of the platforms are in relatively shallow water. The discharge of production and drilling chemicals, residual oil and compounds derived from the formation water co-produced with the oil or gas contribute to the contamination concentration in sediments and water. However, in Liverpool Bay and Morecambe Bay, where the oil and gas fields are located, the riverine inputs of major groups of organic contaminants and metals are found to be several orders of magnitude greater than those from the offshore oil and gas industry.

Inputs of artificial radionuclides into the Irish Sea are dominated by discharges from Sellafield on the Cumbrian coast. The distribution of radionuclides in seawater, in the sediment and in biota are reviewed.