Pesticide management and their residues in sediments and surface and drinking water in the Mekong Delta, Vietnam

Public concern in Vietnam is increasing with respect to pesticide pollution of the environment and of drinking water resources. While established monitoring programs in the Mekong Delta (MD) focus on the analysis of organochlorines and some organophosphates, the environmental concentrations of more recently used pesticides such as carbamates, pyrethroides, and triazoles are not monitored. In the present study, household level pesticide use and management was therefore surveyed and combined with a one year environmental monitoring program of thirteen relevant pesticides (buprofezin, butachlor, cypermethrin, α-endosulfan, β-endosulfan, endosulfan-sulfate, fenobucarb, fipronil, isoprothiolane, pretilachlor, profenofos, propanil, and propiconazole) in surface water, soil, and sediment samples. The surveys showed that household level pesticide management remains suboptimal in the Mekong Delta. As a consequence, a wide range of pesticide residues were present in water, soil, and sediments throughout the monitoring period. Maximum concentrations recorded were up to 11.24μgl−1 in water for isoprothiolane and up to 521μgkg−1dm in sediment for buprofezin. Annual average concentrations ranged up to 3.34μgl−1 in water and up to 135μgkg−1dm in sediment, both for isoprothiolane. Occurrence of pesticides in the environment throughout the year and co-occurrence of several pesticides in the samples indicate a considerable chronic exposure of biota and humans to pesticides. This has a high relevance in the delta as water for drinking is often extracted from canals and rivers by rural households (GSO, 2005, and own surveys). The treatment used by the households for preparing surface water prior to consumption (flocculation followed by boiling) is insufficient for the removal of the studied pesticides and boiling can actually increase the concentration of non-volatile pollutants. ► Household level pesticide management remains suboptimal in the Mekong Delta, Vietnam. ► A wide range of pesticides occurs in water, soil, and sediments of fields and canals. ► Water for drinking is often derived from surface water by households in rural areas. ► Environmental concentrations lead to chronic exposure of aquatic organism and humans. ► Common treatment of surface water for drinking can enhance pesticide exposure.