The National Performance Framework Clean Seas Indicator 2018 is the percentage of assessments of metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in biota and sediment showing concentrations that are unlikely to harm marine organisms in Scottish waters. The Indicator is based on a series of regional assessments in which the mean concentration of each contaminant is compared to the Environmental Assessment Criteria (EAC) or an equivalent threshold when the EAC has not been established. The regional assessments are themselves based on the 2018 assessment of the UK's Clean Seas Environment Monitoring Programme (CSEMP).