Omdat vervuiling niet bij de grens stopt, moeten we ook onze buurlanden oproepen ons strikte kwikbeleid uit te voeren. ###>It is already evident that the principle of substitution applies here, and that is made all the more important by the fact that mercury is not bio-degradable and so it is permanently in circulation; every single microgram of it will keep on coming back to human beings through the food chain.