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This report draws on a wide range of data sources to provide an overview of the chemicals used in the offshore oil and gas industry, of the chemicals already in the environment and of those released into the environment from other sources.

Considering the whole sea area, it should be noted that the water samples with the highest levels of chemical contamination are found at inshore estuary and coastal sites subject to high industrial usage.

Approximately 2,000 chemical products are used by the offshore oil and gas industry. In 1999 some 180,000 tonnes of chemicals were discharged into the UK sector of the North Sea.

Produced water is now the main source of contaminants, having overtaken drill cuttings since oil-based muds were replaced by less harmful alternatives.

24,286 tonnes of chemicals were reported as discharged to the UKCS in produced water in 1999.

The quantity of oil production water is greater than of gas production water. As oilfields mature, the amount of produced water increases.

The range of chemicals used by the offshore oil and gas industry, the means of regulating them and of monitoring their use, are discussed.

Evidence of biological effects caused by the release of contaminants into the sea is reviewed.

This report draws on a wide range of data sources to provide an overview of the chemicals used in the offshore oil and gas industry, of the chemicals already in the environment and of those released into the environment from other sources. Considering the whole sea area, it should be noted that the water samples with the highest levels of chemical contamination are found at inshore estuary and coastal sites subject to high industrial usage.

Approximately 2,000 chemical products are used by the offshore oil and gas industry. In 1999 some 180,000 tonnes of chemicals were discharged into the UK sector of the North Sea. Produced water is now the main source of contaminants, having overtaken drill cuttings since oil-based muds were replaced by less harmful alternatives. 24,286 tonnes of chemicals were reported as discharged to the UKCS in produced water in 1999. The quantity of oil production water is greater than of gas production water. As oilfields mature, the amount of produced water increases.

The range of chemicals used by the offshore oil and gas industry, the means of regulating them and of monitoring their use, are discussed. Evidence of biological effects caused by the release of contaminants into the sea is reviewed.

This report was prepared by scientists from the Centre for Environment, Fisheries and Aquaculture Science (CEFAS). CEFAS is a UK-based research and consultancy centre providing services in fisheries science and management, environmental monitoring and assessment, and fish health.

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.

The report concludes with a discussion of gaps in our understanding. More data on contaminant concentrations are needed within a few kilometres of oil and gas installations. In particular, compounds commonly detected in produced water should be characterised for both Morecambe Bay and Liverpool Bay in order to enable the accurate calculation of the contribution of the offshore industry to chemical loads. This may increase in importance as land based discharges come under greater control and produced water increases.

This report was prepared by scientists from CEFAS.

In advance of SEAs for areas 6, 7 & 8, a series of data assessment projects were instigated. The purpose of these projects was to assess the extent, quality and accessibility of data relating to specific environmental factors. In some cases, the project leaders produced brief explanatory notes describing the environmental factor being considered, in other cases the project was limited to a data search alone.

The contractors were asked, where possible, to enter the data onto an "End-Note®" database file in order that bibliographic searches may be made.

Please note that the boundary between SEAs 6 and 7 changed during the time these reports were produced, so may appear in a different position in some reports.

In advance of SEAs for areas 6, 7 & 8, a series of data assessment projects were instigated. The purpose of these projects was to assess the extent, quality and accessibility of data relating to specific environmental factors. In some cases, the project leaders produced brief explanatory notes describing the environmental factor being considered, in other cases the project was limited to a data search alone.

The contractors were asked, where possible, to enter the data onto an "End-Note®" database file in order that bibliographic searches may be made.

Please note that the boundary between SEAs 6 and 7 changed during the time these reports were produced, so may appear in a different position in some reports.

In advance of SEAs for areas 6, 7 & 8, a series of data assessment projects were instigated. The purpose of these projects was to assess the extent, quality and accessibility of data relating to specific environmental factors. In some cases, the project leaders produced brief explanatory notes describing the environmental factor being considered, in other cases the project was limited to a data search alone.

The contractors were asked, where possible, to enter the data onto an "End-Note®" database file in order that bibliographic searches may be made.

Please note that the boundary between SEAs 6 and 7 changed during the time these reports were produced, so may appear in a different position in some reports.