Assessment of environmental fate and exposure variability of organic contaminants

Advanced fate assessment and its application/implication for hazardous chemicals is discussed. The spatially resolved fate assessment of chemicals has been performed using a newly developed spatially resolved multimedia environmental fate model (G-CIEMS: Grid-Catchment Integrated Modeling System) based on the geographical information system environment. The G-CIEMS modeling system has roughly 5 X 5-km resolution on the entire Japanese terrestrial region, combining a gridded-air and catchment-based surface and river geographic structure. A summary of the model description is given and validation results are discussed, which showed generally acceptable agreement between measured and simulated environmental levels for several tested chemicals. By applying the results of spatially resolved environmental concentration, the geographic distribution of exposure to humans is estimated, which showed that the majority of exposure occurred in Japan's land area with higher environmental concentration at the level of 99 percentiles or higher. The impact on the geographic distribution of environmental levels on human exposure from fish is analyzed based on monitoring, modeling, and several social and fisheries statistics. The results of estimation were compared to those of total diet studies. The estimated results are in a range close to the results of the total diet survey and thus basic validation was achieved in this study. However, as the nature of samples differed, more in-depth comparison may be necessary for future study.