Scale residues can accumulate on the interior surfaces of subsea petroleum pipes and may incorporate naturally occurring radioactive materials (NORMs). Following a scenario of in-situ decommissioning of a subsea pipeline, marine organisms occupying the exteriors or interiors of petroleum structures may have close contact with the scale (metal and radionuclide contaminants). Consequently, radioecotoxicological effects from the chemical and radiological properties of the scale could occur. This presentation will describe a tiered approach to assess the ecological impacts of pipeline scale using: 1) synchrotron-XFM to characterise NORM-contaminated scale; 2) a series of marine infauna-exposure tests to understand the bioaccumulation and organ biodistribution of scale-associated constituents; and 3) radiological biota dose modelling under different decommissioning. As illustrated here, using a multidisciplinary approach can further aid our understanding of the fate of NORM contamination products in subsea oil and gas systems and guide Australia-specific risk assessments for infrastructure decommissioning options. The creation of a tiered assessment will enable industry to optimise decommissioning solutions and allow the regulator to set clearer expectations on environmental protection requirements.