Computer graphics representation of a molecule of DDT (diphenyldichlorotriphenylethane), an insecticide. DDT was first synthesized in 1873, but 60 years were to pass before its insecticidal properties were realised by the Swiss chemist Paul Muller. This was soon followed by the discovery of other chlorinated hydrocarbon insecticides such as benzene hexachloride & Dieldrin. Unfortunately, such chemicals persisted in the environment and entered the food chain, with disastrous effects on some bird populations. Also, DDT-resistance insect strains were beginning to evolve. During the 1970's the widespread use of DDT was banned in many countries.