ABSTRACT
During the latter part of the twentieth century a number of pollution problems came to be recognized. In the developed world this discovery led to the introduction of restrictions and outright bans on the marketing and use of certain chemicals. Prominent examples included persistent organochlorine insecticides such as DDT, aldrin, dieldrin, and heptachlor, methylmercury fungicides, and polychlorinated biphenyl (PCB) mixtures. In many cases these measures, in the longer term, led to the decline of environmental residues and some recovery of populations that had been adversely affected. Evidence of this has come from long-term studies in North America and Western Europe, which are described in Section 2 of this book. Thus, bans on DDT were followed by some recovery of affected populations of predatory birds in the area of the Great Lakes of North America, and bans of aldrin and dieldrin in Great Britain were followed by recovery of raptors such as peregrines and sparrowhawks (Chapter 9). Not all has been easy sailing, though. In some badly affected areas of North America unacceptably high levels of pollution have continued to exist even into the present millennium. Examples include continuing pollution by methylmercury, PCBs, and dioxins. Also, there is still concern about the misuse of pesticides in the developing world.
