The environmental pollution caused by plastics and their chemical additives has drawn global attention. The ultraviolet absorber UV-328 is one of the most commonly used UV stabilizers in plastic products to protect against discoloration and degradation under sunlight. It is recognized as harmful due to its persistence, bioaccumulation, adverse effects, and potential for long-range environmental transport, has been listed as Persistent Organic Pollutants (POP) under Annex A to the Stockholm Convention for global elimination of all production in 2023. Marine plastic debris is a vector for long-range transport and consistent releasing point sources of UV-328. However, baseline data on UV-328 in marine plastic debris is still very limited, especially in the Southeast Asia region, which is a global marine plastic pollution hotspot. The proposed CRRP aims to combine both field sampling and laboratory simulation methods to conduct a collaborative regional survey of UV-328 in marine plastic debris and surrounding waters in typical coastal and estuarine sites of China, Malaysia, Philippines, Thailand and Vietnam. The outcomes of this project are expected to provide the first baseline data of UV-328 occurrence in marine plastic debris in Southeast Asia, which could eventually provide important scientific support for evaluating the environmental risks of UV-328 and informing scientific management and policymaking.