The WHO Recommended Classification of Pesticides by Hazard has been published since 1975, has been revised and reissued every few years and has gained wide acceptance. This document sets out a classification system to distinguish between the more and the less hazardous forms of selected pesticides based (mainly) on acute risk to human health (that is the risk of single or multiple exposures over a relatively short period of time). It takes into consideration the toxicity of the technical compound and its common formulations. The document lists common technical grade pesticides and recommended classifications together with a listing of active ingredients believed to be obsolete or discontinued for use as pesticides, pesticides subject to the prior informed consent procedure, limitations to trade because of the POPs convention, and gaseous or volatile fumigants not classified under these recommendations.