Ecotoxicological effects of decommissioning offshore petroleum infrastructure: a systematic review

Successful decommissioning of subsea oil and gas infrastructure requires a safe and effective approach to assess and manage waste products. These products, often present as scale on internals of pipelines, include naturally occurring radioactive materials (NORM) and trace metals. Understanding the potential biological effects of these contaminants on marine fauna is crucial to managing global decommissioning. A systematic review was conducted, and information extracted from available literature on the biological effects of contaminants on marine organisms and current environmental regulations of petroleum-associated NORM management. Studies defining the chemical and radiological effects from decommissioned structures were limited. The main source of contaminants was identified from offshore platforms, with none from subsea structures. Only three studies measured variable chemical effects of radium to organisms from scale materials in subsea oil and gas infrastructure. Current international regulations are absent for the closure of subsea pipelines with NORM being underreported and not addressed in environmental impact assessments. This review highlights research gaps from environmental monitoring and characterisation of NORM associated with decommissioned structures. Key recommendations for future research include using available techniques to monitor and characterise NORM scale and assess effects of scale to marine organisms through direct organism exposure experiments. This study provides guidance for the formation of appropriate risk assessments and decommissioning decisions incorporating ecotoxicological principles.