A first list of dangerous substances to supervise was drawn up by the Environmental Protection Agency - EPA (the USA). International Conventions (e.g. Oslo-Paris) attempted to give priorities among the substances.This list was since reduced, but twenty five years of observations (in continuous protocols) along the French littoral, allow to draw up an objective assessment of the levels of contaminations, recorded progress, remanent deteriorations, and of the effectiveness of measures taken.The time-constants recorded before observing the results of these measures are important: they integrate the physicochemistry of the coastal and estuary processes, but also inertia, even hysteresis of the socio-economic system which implement these measures