Occupational Exposure to Pesticides Applied by Rice Growers in Malaysia

Abstract There is a sparsity of information about occupational exposure to pesticides on small-scale farms in developing countries. This study investigates rice growers’ exposure to pesticides due to the use of knapsack/backpack sprayers, a practice which is widespread in developing countries including Malaysia. Pesticide application information was collected from 23 rice growers during November 2020 – March 2021 using personal interviews and questionnaires. The information was used to predict total daily exposure to individual active substances via dermal and inhalation routes during mixing/loading and application activities using selected exposure models. The estimated exposures were assessed against the agricultural operator exposure levels (AOELs) for single active substances, where any exceedance indicates a potential risk to health. The 23 rice growers cultivated 0.6 – 3.8 ha of rice. Pesticides were applied on 3 -13 different days by the different growers with between 1 and 8 compounds applied on individual spray days. Individuals had estimated average daily exposures to single active substance compounds of 4.1x10-3 to 1.3x10-1 mg kg-bw-1 day-1 (4.0x10-3 – 1.3x10-1 and 4.2x10-5 – 5.4x10-2 mg kg-bw-1 day-1 during application and mixing/loading activities, respectively), where dermal exposure constituted 89 – 99.6% of the total exposure. Overall, 25% of all the applications reported by the 23 growers had exposure estimates that exceeded the AOELs, mainly due to the use of highly toxic pesticides, products formulated as wettable powders, and/or growers neglecting to wear gloves whilst handling pesticides. All of these factors can be improved by provision of training and information on selection of pesticide products and application practices. Study findings can be used to target efforts to minimise pesticide risks to health in developing countries.