ABSTRACT
During the second half of the 20th century, it was discovered that a number of organic pollutants (OPs) were having harmful side effects in natural ecosystems, prominent among which were chemicals that combined high toxicity (lethal or sublethal) with marked biological persistence. Examples such as dieldrin, DDT, TBT, and methyl mercury are represented in Part 2 of the present book. Following these discoveries, restrictions and bans on the release of these chemicals into the environment were introduced in many countries. Persistent organochlorine (OC) insecticides, for example, were withdrawn from many uses and replaced by less persistent OP and carbamate insecticides. More stringent legislation was brought in to control the production and marketing of new chemicals, with clearer guidelines for environmental risk assessment. Particularly strict rules were applied to new pesticides-something of a double-edged weapon. This tightening of regulations has reduced the risk of new pesticides creating new problems, but it may also have impeded the discovery and registration of newer, more environmentally friendly compounds by making research and development too expensive. In spite of the immediate advantages tighter regulations bring, they can, in the long run, be counterproductive.
