In simplified diagrammatic fashion, Figure illustrates the approximate chronological succession of environmental hazards, as societies undergo eco- nomic growth and consequent increases in the scale of human activity and envi- ronmental impact (4). Historically, on a local scale, category A hazards have predominated. In the early years of the industrial revolution in Europe much of the environmental hazard was at household and neighbourhood level. In the middle decades of the twentieth century developed countries began to reduce the levels of category B hazards, often via environmental legislation—such as the clean air acts of European and North American countries. Today, category C hazards are increasing, reflecting the great pressures.
