The best known causes of macroplastics from shipping are the loss of cargo and general waste going astray. Microplastics are also discharged with greywater and sewage, as well as from wear of ropes and the peeling of marine paint.
Loss of cargo
Loss of cargo can be caused by extraordinary conditions such as inclement weather, collisions and groundings, but incidents can also occur during normal conditions if the load has not been secured properly. Overloading or other conditions can lead to destabilisation, for example due to miscalculation of ballast, the vessel tilting or safety equipment failing.
Containers that end up in the sea often become damaged and the contents end up being spread across large areas. This can lead to extensive pollution of the sea and beaches. This was experienced in connection with incidents such as when several thousand rubber ducks were lost in the Pacific Ocean in 1992 and when a container carrying plastic pallets was damaged in the North Sea in 2020. Plastic pellets are often packaged in large quantities and without separate compartments. It is difficult to stop the pellets from escaping uncontrollably when such packaging is damaged. Plastic pellets spread rapidly in the water and constitute a significant threat to marine life, while also being very difficult to collect.
Waste gone astray
In the same way as on land, accessibility and well-functioning waste systems are crucial to ensuring proper follow-up procedures and attitudes when it comes to waste management. International legislation, which sets out requirements for the reporting and management of waste on board has helped reduce the dumping of waste at sea. Nevertheless, waste does still end up going astray in some situations. External circumstances have previously been mentioned, but lack of waste systems, overflowing waste containers and activities associated with repairs or production can also lead to waste ending up going overboard.