Appraises the risks to organisms and ecological systems posed by the use of 2,4-dichlorophenoxyacetic acid (2,4-D), a selective herbicide which kills broad-leaved plants but not grasses or conifers. Evaluation is restricted to studies conducted at exposures that could be expected in the field. The opening sections underscore the importance of the physico-chemical properties and formulation of 2,4-D on its behaviour in environmental compartments. Against this background, separate sections are then devoted to the evaluation of risks to microorganisms, aquatic organisms, and terrestrial organisms. Numerous tables are used to summarize the large number of studies indicating toxicity to different species, no-observed-effect levels in different species, and variations in the toxicity of different formulations. The final section considers data on ecological effects from field applications. On the basis of the evidence reviewed, the book concludes that, when used under field conditions and at recommended rates, 2,4-D does not appear to produce direct toxic effects on any animal species