博士 / 國立臺灣大學 / 生物環境系統工程學研究所 / 97 / Arsenic (As) in seafood receives public attention because it is potential hazardous to human health and frequently presents at high concentration levels. Humans are exposed to various sources of As (food, water, soil and air), but exposure via ingesting seafood is by far the most important one. This study estimates the potential carcinogenic risk of ingesting inorganic As in aquacultural fish and shellfish in the blackfoot disease (BFD) hyperendemic areas of Taiwan, using geostatistical methods and geographic information systems. Five aquacultural species, tilapia (Oreochromis mossambicus), milkfish (Chanos chanos), mullet (Mugil cephalus), clams (Meretrix lusoria) and oysters (Crassostrea gigas), are taken into account. We herein construct a rational ingestion risk diagram with considering the concentration of inorganic As and risk-based daily ingestion rate of aquaculture species. Moreover, the rational consumption rates of fish and shellfish farmed in As-affected groundwater areas are evaluated. Target cancer risks (TRs) of ingesting As contents in aquaculture fish and shellfish are spatially mapped to assess potential risks to human health and to elucidate the safety of As-polluted groundwater use in fish ponds. Owing to sparse measured data, Monte Carlo simulation and sequential indicator simulation are used to propagate the uncertainty and assessed parameters. For the first assessment (Chapter 2), the human health risk associated with ingesting inorganic As through consumption of farmed oysters in Taiwan is estimated. The results reveal that the ratio of mean concentration among the four townships of inorganic As to total concentration of As in oysters is approximately 1.64%. The estimated target cancer risks (TR), based on a 95% occurrence probability from ingesting inorganic As by consuming oysters at a rate of 18.6–56 g/day, range from 1.26×10-5 to 3.82×10-5. Moreover, a target hazard quotient (THQ) associated with ingesting inorganic As through oyster consumption at a rate of 18.6–56 g/day range from 0.071 to 0.214. Based on the estimation of the TR model, an ingestion rate of 1.6 g/day is recommended to meet the 95th percentile of carcinogenic risk, 10-6, for exposure to inorganic As through the consumption of oysters in Taiwan. Furthermore, this study investigated the relationship between As content in clams and their environment, including sediment and pond water (Chapter 3). The bioaccumulation of As in clams in their exposure environment and the potential carcinogenic risks associated with the ingestion of As in aquaculture clams are probabilistically evaluated. The average ratios of inorganic As contents to total As contents in clams ranged from 12.3% to 14.0% which are much higher than that found in the farmed oysters, indicating that humans may expose to larger quantities of inorganic As by ingesting the same amount of clams as oysters. The results of the risk assessment indicate that potential carcinogenic risks associated with consumption of clams from the BFD area rangs from slightly (4.52×10-6) to largely (80.7×10-6) exceeding the acceptable target risk. Based on the estimation of the TR model, a 0.18 g/day-person of the safe ingestion rate of clams in the BFD region is recommended. For integration of spatial information, an integrated GIS-based approach for assessing potential carcinogenic risks via food-chain exposure of ingesting inorganic As in aquaculture species in the As-affected groundwater areas is presented (Chpater 4). The analyzed results reveal that clams farmed in the western coastal ponds and milkfish farmed in the southwestern coastal ponds have the high risks to human health and tilapia cultivated mainly in the inland ponds only has high risks at the 95th percentile of TR. As-contaminated groundwater used for clams and milkfish ponds should be significantly reduced. The fact that mullet has low risks to human health revealed that As-affected groundwater can be used successively in mullet ponds. Finally, with the goal to propose the suitable consumption rates of seafood, five aquacultural species, tilapia, milkfish, mullet, clams and oysters farmed in As-affected groundwater areas are taken into account to estimate the risk-based rational consumption rates (Chapter 5). Based on the provisional tolerable weekly intake (PTWI) of 15 μg inorganic As/kg body weight suggested by the Food and Agriculture Organization/World Health Organization (FAO/WHO), the daily basis of inorganic As intake of 6.37 μg/day for provisional tolerable daily intake for fish and shellfish (PTDI ) for an adult Taiwanese is transformed. The total dietary intakes estimate for inorganic As in fish and shellfish are 0.52, 1.20, 2.17, 3.95 and 9.22 μg/day, respectively, for 5th, 25th, 50th, 75th and 95th percentiles.The 95th percentile of 9.22 μg/day is higher than PTDI. The rational consumption rate of fish and shellfish is evaluated based on the maximum acceptable lifetime risk. According to the relationship between concentrations of inorganic As (Cinorg) and risk based daily ingestion rate (RBIRf), a tolerance zone with risk range from 1×10-5 to 6.07×10-5 is graphically constructed to define the rational consumption rate of fish and shellfish for general public in Taiwan
The study concludes that the integration of spatial information in assessing and managing potential carcinogenic health risk via ingestion of farmed fish and shellfish in blackfoot disease hyperendemic areas has been proposed. It suggests an effective framework for public health officials in Taiwan in assessing potential carcinogenic risks and informs consumers to wisely choose aquacultural products from As-affected groundwater areas.
| Identifer | oai:union.ndltd.org:TW/097NTU05404003 |
| Date | January 2008 |
| Creators | Ching-Ping Liang, 梁菁萍 |
| Contributors | Chen-Wuing Liu, 劉振宇 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 112 |
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