In recent years there has been an increasing awareness of plastics entering the sea from blasted rock. There is a need for further knowledge and information about this and which type of prevention and measures that can be taken to stop the plastics from entering the sea or stop the spreading of plastics that already have entered the sea. This report describes how plastics originating from placement of rock masses from tunnelling and other blasting activities can be prevented from entering the sea. During tunnel construction plastics are used in many different components such as explosives, lead wires and detonators as well as in fibrous reinforcement of shotcrete linings in tunnels. By implementing relatively simple measures, it is estimated that a minimum 75 % reduction of spreading of plastics to the sea from tunnelling and blasting compared to today’s situation should be possible.