Emission Control Area (ECA)

An Emission Control Area is a sea area designated under MARPOL Annex VI where stricter limits apply on sulphur oxides, nitrogen oxides, or particulate matter. The Baltic, North Sea, North American, and US Caribbean ECAs enforce a 0.10% sulphur cap on fuel against the 0.50% global cap, and NOx ECAs require Tier III engines on newer ships. The Mediterranean became a SOx ECA in May 2025. ECAs concentrate the toughest air-quality controls where shipping traffic meets populated coasts.