Plastic is a single word for a multifaceted reality, encompassing a wide variety of polymers and additives with different chemical and physical properties. The end products range from single-use plastic bags, food wraps and plastic bottles, to fishing lines, buoys, and synthetic fibres used in the clothing or fishing industries.As the use of plastic is pervasive, so is plastic pollution. An estimated 10 million tonnes of plastic leaks into the ocean each year, causing an unprecedented environmental crisis. Measuring or forecasting this issue is a complex and challenging task, due to technical limitations and uncoordinated assessment campaigns. Acting to tackle this issue requires adequate metrics to guide and prioritise action at different levels, ranging from sound product design and efficient regional infrastructure, to adequate policies and enforcement.