Pesticide Use and Management in the Mekong Delta and their Residues in Surface and Drinking Water

Abstract

Pesticides are essential inputs in agricultural production to control target pests and thus to improve crop yields. Appropriate use and management of these chemicals and reduction of its negative influences on human health and the environment are global concerns. In the Mekong Delta, Vietnam, an area which contributes more than 90% to the country’s rice exports, pesticides have been increasingly applied since the so called Doi Moi (renovation). In this present study, two representative areas were selected to conduct different studies related to 1) pesticide use and management at household level, 2) resulting residue concentrations in surface water in fields and irrigation canals, 3) treatment practices of surface water for the purpose of drinking, and 4) pesticide concentrations in drinking water derived from surface water. One study area is characterized by intensive rice cultivation in Tam Nong District, Dong Thap Province, while the second area was selected as a representative for a peri-urban site mixed agricultural production pattern in Cai Rang District, Can Tho City. Surveys and monitoring campaign were carried out from August 2008 to August 2009. Survey results indicated that a majority of respondent farmers improperly used and managed pesticides. The study found that organochlorine and organophosphorus pesticides were less used while several pesticide groups such as pyrethroid, conazole, biopesticide and amide were being frequently applied. Half of investigated pesticides belong to moderately and slightly hazardous categories according to WHO hazard classification. 12 out of 15 studied pesticides (buprofezin, butachlor, cypermethrin, difenozonazole, α-endosulfan, β-endosulfan, endosulfan-sulfate, fenobucarb, fipronil, hexaconazole, isoprothiolane, pretilachlor, profenofos, propanil and propiconazole) were quantified in surface water in fields and irrigation canals, with average concentrations ranging from 0.02 to 3.34 μg/L and from 0.01 to 0.37 μg/L at the intensive rice cultivation and mixed agricultural production areas, respectively. Monitoring of pesticide residues in drinking water quantified seven out of 15 studied pesticides, with average concentrations ranging from 0.01 to 0.47 μg/L. The study also revealed that aluminium sulfate and boiling practice, frequently applied to treat surface water for drinking by respondent farmers, unfortunately could not remove the most of studied pesticides from drinking water. Consequently, as compared to European Commission guideline values for drinking water local people were exposed to several pesticides which might pose their health at risk. The present study provides and discusses possibly measures in order to improve pesticide management practices as well as to decrease pesticide inputs into water ecosystems and thus reduce the exposure of (rural) people to these potentially harmful chemicals.