Bioaccumulation And Metablisom Of Typical Organic Pollutants In Fish And Human Exposure Via Fish Consumption

Amount of organic pollutants,such as well-known dichlorodiphenyltrichloroe-thane?DDTs?and polychlorinated biphenyls?PCBs?,and emerging carbazole and polyhalogenated carbazoles?PHCZs?,have been released into environment with the growth of industry.Because most of organic pollutants exhibit potential biological and human health risk effects,their concentrations and bioaccumulation in organism have been paied great attention.Fish intake was considered as the main pathway of human exposure to organic pollutants.Previous studies focused on the accumulation of DDTs and PCBs in cultured fish,while few researches have evaluated their accumulation and human health risk in wild fish.In addition,carbazole and PHCZs have been frequently detected in soils and sediments,but their accumulations in fish have not been demonstrated.Therefore,the present study was conducted to?1?evaluate human health risk of local residents through dietary exposure to DDTs and PCBs in wild fish collected in the surrounding coastal areas of Hong Kong;?2?examine the accumulation and metabolism of carbazole and PHCZs in tilapia thourgh dietary exposure to spiked feed with PCBs as references.The results indicate that the concentrations of DDTs and PCBs in 31 kinds of wild fishes were in the ranges of 0.44?17 and 0.028?6.3 ng?g^-1 ww,respectively,which were at the low end of global ranges.Spatially,the lowest concentration of DDTs and PCBs were found in the west of Lantau Island and Tolo Harbor.Furthermore,fish feeding habit and their living environments could have some influences on their accumulations of DDTs and PCBs.Source diagnostics indicated that DDTs in these fishes mainly originated from historical residues,but the fishes which migrate relatively longer distances may be subject to DDTs contamination in the estuaries.Finally,he potential increased lifetime cancer risk of local adolescences and adults exposed to DDTs and PCBs via wild fish consumption was high.As a result,the local residents in Hong Kong should reduce the daily intake of wild fish from its surrounding coast regions.During the dietary exposure test,the concentration of carbazole,PHCZs and PCBs in the spiked fish feed were 60?83,43?214 and 4?6 ng g^-1 ww,respectively.The accumulated levels of three target compounds in the fish were in the ranges of8?350,34?646,6300?12000 ng g^-1 ww,respectively.Carbazole and PHCZs were mainly distributed in the liver and gill,whereas PCBs were dominantin gill.The concentrations of PCBs in tilapia tissues were significantly higher than those of carbazole and PHCZs.During the exposure period?0?176 days?,the PCBs concentration in the fish increased gradually with exposure time,while carbazole and PHCZs did not exhibit the similar trends.These results have indicated that carbazole and PHCZs may not be accumulated in tilapia.The greatest abundance of carbazole was found in activated carbon used in the circulating water tank,whereas those of PHCZs and PCBs were observed in fish fecesand suspended particles in water.The dietary assimilation efficiencies of carbazole and PHCZs in tilapia were 0.0017%and 0.0002?0.0007%,respectively,far less than PCBs?2.6?4.3%?.Results from mass balance analysis showed that the total mass of carbazole and PHCZs in the exposure system only accounted for 0.3%and 0.3?6.7%of the total exposure amount,less than those of PCBs?21?44%?.In addition,eleven methoxy metabolites of carbazole and PHCZs were found in the fish feces and water,including methoxyl carbazole,methoxy-monobromo-carbazole,methoxy-dichloro-carbazole,methoxy-dibromo-carbazole and methoxy-tribromo-carbazole.Therefore,all findings suggested that carbazole and PHCZs exhibit the weak characteristics of bioaccumulation in tilapia.