Assessment of occupational exposure to pesticides applied in rice fields in developing countries: a critical review

Rice is a globally-significant staple cereal for which cultivation is concentrated in developing countries and, to a large extent, in smallholder farms. There is significant potential for operator exposure to pesticides during such rice production, but research to date is fragmented. This review evaluates methods and outcomes of studies to quantify pesticide exposure amongst rice growers in developing countries. Knapsack sprayers are used very frequently in rice cultivation, but existing exposure estimation methods lack the functionality to generate robust estimates of exposure. Direct measurement methods have been applied in a range of developing countries to measure dermal contact and/or respiratory inhalation during pesticide handling activities, and these have sometimes been coupled with biological monitoring for exposure. Only a few studies have collected contextual information in parallel with exposure assessment, using interviews or questionnaires to capture information on agricultural practices and personal protective measures. There is general agreement that dermal exposure is likely to be larger than inhalation exposure, with dermal contact exacerbated by risk factors including crop structure, maintenance status of equipment, and use of any personal protective equipment. There is frequent use within the reviewed studies of pesticide active substances that have been restricted in other parts of the world. Overall, there is an urgent need for more systematic studies to address gaps in knowledge and improve exposure estimates for use in health analysis and risk assessment.