ORCID

Document Type

Article

Abstract

Accumulation of end-of-life plastic is a global environmental problem. Plastics are widely used in oil and gas infrastructure and bring considerable benefits while in service. However, the environmental consequences of end-of-life decommissioning scenarios are largely unknown. Using the UK Continental Shelf (UKCS) as a case study we estimate the mass of plastics deployed in subsea pipelines, quantify degradation and estimate the rate of microplastic generation. Recognising that the relatively slow rate of any subsequent mineralisation leads to an accumulation of plastic particles in the marine environment, we then apply a novel approach using Predicted No-Effect Concentration (PNEC) analysis to estimate potential environmental risks of decommissioning in situ. We demonstrate physical and chemical degradation of oil and gas plastics after 22 years in the UKCS. Available data indicated 121,000 tonnes of plastics may be decommissioned in situ, and we estimate that depending on environmental conditions their degradation could generate 4.5–500 tonnes of microplastics annually. Our lowest release scenario is a similar order of magnitude to the annual releases of microplastics to the North Sea from UK rivers and our highest is considerably more than annual microbead releases from cosmetics prior to the UK ban. Moreover, our PNEC analysis indicates microplastics generated from legacy oil and gas plastics have the potential to harm marine life. Despite uncertainties in absolute levels of microplastics generated from oil and gas legacy plastics we recommend they are formally integrated into decommissioning decision-making and into planning and consenting of new installations, including offshore renewable energy infrastructure.

Publication Date

2026-09-15

Publication Title

Journal of Hazardous Materials

Volume

516

ISSN

0304-3894

Acceptance Date

2026-07-19

Deposit Date

2026-10-08

Funding

This research was funded as part of the INSITE North Sea Programme project “Decommissioning of subsea plastics in the UK oil and gas industry” (Phase I and II) awarded to Howell Marine Consulting. The authors appreciate the opportunity to conduct independent scientific research supported by the INSITE Industry Expert Committee (IEC) comprising representatives from oil and gas operators in the UKCS who provided support and expertise, in addition to samples of pipelines and umbilicals from Brent Field. Thanks to Kieran Monk, Billy Simmonds, Francesca De Falco, Alexander Mead and Glenn Harper (University of Plymouth) for technical support and Hannah Whitman (Science Animation Studio and University of Plymouth) for creating the graphical abstract.

Keywords

Estimating environmental risk, Marine infrastructure, Microplastics, Policy framework, Polymer degradation

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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