DIFFUSE SOURCES OF POLLUTION BY HEAVY-METALS

Significant reductions in the amount of heavy metals released to the aquatic environment have been achieved by applying strict controls on point source industrial discharges. Because of these tight controls, diffuse pollution sources have increased in importance as a contribution to the total load. Diffuse inputs originate mainly from the use of chemical products. Thus control of these inputs can be achieved by refraining from or limiting the use of these products or by restricting the amount of heavy metals permitted in such products. Control of diffuse sources of heavy metals could be based on a 'positive approval' system, permitting only those uses which do not lead to environmental harm and which could not be replaced by less harmful alternatives. Assessing the environmental impact of the alternatives will require the introduction of a 'cradle to grave' approach.