BIOAVAILABILITY OF ARSENIC IN ECOSYSTEM WITH SPECIAL REFERENCE TO AQUACULTURAL FISH AND POTENTIAL HEALTH RISKS

The widespread incidence of chronic arsenicosis in Chianan plain, SW Taiwan has led to intensive research on arsenic (As) enrichment in groundwater as well as accumulation in foodstuffs, as there are potential health risks associated with exposure to As. This study deals with bioavailability of arsenic in locally grown foodstuffs (e.g. crops and vegetables) and aquacultural fish in part of Chianan plain. Groundwater and foodstuffs were collected and analyzed to estimate the total As contents. Major crops like rice and maize showed a considerable amount of As, with mean values of 112 and 73 µg kg^-1, respectively. Significant levels of As were also found in other common crops and vegetables cultivated in this area. Aquacultural tilapia (Oreochromis mossambicus L.) from groundwater-cultured ponds in southwestern Taiwan (Budai, Yichu and Beimen) were analyzed to estimate the arsenic (As) bioaccumulation and the potential health risk to human intake. Arsenic concentrations in tilapia in Budai (0.33-1.58 mg kg^-1) were found to be higher than those in Yichu (0.79-1.07 mg kg^-1) and Beimen (0.73-0.78 mg kg^-1). Arsenic content in tilapia is correlated (r²=0.80) with arsenic concentration of pond water. Arsenic concentration in total fish is also correlated with that in bone (r²=0.98), head (r²=0.97) and tissue (r²=0.96). Among three different arsenic species studied, organic species of DMA (dimethyl arsenic acid sodium salt) was found dominant to inorganic species of As(III) and As(V). The values of TR (target cancer risk) and THQ (Target Hazard Quotient) for all fish were very high (2.9×10^-4 to 13.9 ×10^-4 and 1.5-7.2, respectively) in comparison to the USEPA safe standard. The results of this study further indicate the potential risk of As exposure to local inhabitants through the food chain which is associated with continuous consumption of As-contaminated foodstuffs. Therefore, more action needs to be taken to control the contamination pathways (such as the water-soil-crop system) to protect from continuous ingestion of As through foodstuffs.