Transboundary Pollution

Transboundary pollution is contamination that originates in one jurisdiction and causes harm in another, crossing national or maritime boundaries through currents, wind, or shared water bodies. In the marine context it covers drifting oil slicks, regional eutrophication, and persistent contaminant transport, and it drives regional cooperation instruments such as the Bonn Agreement, OSPAR, HELCOM, and the UNEP Regional Seas action plans. The OPRC Convention 1990 frames mutual assistance for spills that breach borders. Customary international law applies the no-harm and polluter-pays principles, requiring states to prevent activities that cause environmental damage beyond their territory.