ABSTRACT
Conclusions and Recommendations This Thesis has examined and compiled the results of a scientific study to identify the practices of use of pesticides in vegetable cultivation in Ghana, and the incidence and magnitude of their on-site and off-site environmental effects. The knowledge of human exposure to and potential public health risks of levels of current-use pesticide residues has been discussed. In addition, the Thesis has identified the data and knowledge gaps that need to be filled by future pesticide residues research and monitoring. The Thesis drew on existing knowledge and incorporated new information from the research funded under the UNESCO-IHE/IWMI/IFS funding programme. The most important conclusions drawn from the study, alongside recommendations, will be presented here. Profile of vegetable pesticide usage Vegetable farmers in Ghana have been applying pesticides for over four decades. Most farmers, particularly those at Akumadan, make two to twelve applications of pesticide in a typical growing season of tomatoes, pepper, eggplants or okra. The pesticides used are organophosphates such as chlorpyrifos and dimethoate, as well as organochlorines such as endosulfan, and pyrethroids such as lambda cyhalothrin, cypermethrin and deltamethrin. Of the 43 chemicals used on sample farms in this Research, only four are registered for general use in Ghana. The others are meant for restricted use or are not registered for use at all. Unsafe pesticide storage, handling, and disposal practices coupled with inadequate education and training, documented in Chapter 2, subject the farmer to high levels of health hazards and contaminate the vegetable ecosystem. Clearly, there is an urgent requirement for well-targeted training programmes for vegetable farmers on the need for and safe use of pesticides. On-site and off-site environmental effects of vegetable pesticides In Chapter 3, field trials were used to understand the fate of a typical pesticide on a vegetable plot. The trial experiments were conducted in a field at Akumadan, the most prominent vegetable cultivating community in Ghana. The field trials, together with the survey of Chapter 2, provided a means to identify “hotspots” of environmental effects and pathways of human exposure of pesticides. The pesticide and vegetable used were endosulfan and tomato (Lycopersicum esculentum), respectively. The selection of the pesticide was based on use, stability (i.e. biodegradability), toxicity and bio-accumulative properties. Tomato was selected for this study because it is widely grown in the study area, related to the use of the selected pesticide and due to the economic importance of its crop.
