Transformations of pesticides in the atmosphere: A state of the art

The current knowledge about transformation rates and products of pesticides in the atmosphere is reviewed. Reactive species and their concentrations i n the atmosphere are presented. Reactions of pesticides with these species (including photolysis) in the gas and the particulate phase are evaluated f rom available experimental data. The potential of estimation methods is dis cussed. Experimental techniques for laboratory and outdoor measurements are reviewed. Finally, an estimation is made of uncertainties in atmospheric l ifetimes due to chemical or physical reactions. It is concluded that the mo st important transformation of pesticides in the atmosphere is due to react ion with OH radicals. Very few experimental data for pesticides are availab le though. The levels of uncertainty in OH radical concentrations are accep table, however, for a proper estimation of atmospheric removal rates due to reactions with OH radicals of those pesticides for which experimental tran sformation rates (of homologues) are available.