NIRE Annual Report 1999

NIRE Annual Report

1999

Exposure Assessment of Chemical Substances by Multi-grid / Multi-media Fate Model

Objectives: A numerical simulation with a model of multi-grid/multi-media type was applied to exposure assessment of polychlorinated dibenzo-p-dioxines (PCDDs) and polychlorinated dibenzo-furans (PCDFs). In Japan, since the greater part of waste is processed by incineration, a lot of small-scale waste incinerators, which is the main source of PCDDs/PCDFs, exist in the high population density region. Therefore, it is necessary to apply the model of multi-grid type to evaluate exposure from two or more sources.

Results: In order to evaluate various exposure routes, the model treats material transports between environment media as shown in Fig. 1 (including sub-models of atmosphere, soil, sediment, river, groundwater, and sea area). The model was applied to the area covering whole Kanto distinct (including Tokyo metropolitan area), where 200 or more incineration plants exist. The analytical domain with a scale of 276 ´ 224 km was discretized into 40 ´ 60 grids with space increments 4.6 ´ 5.6 km. The gridded emission inventory of PCDDs/PCDFs in the analytical domain was compiled based on the published monitoring data on exhaust gas, the waste amount and the location of each municipal incineration. Exposure level at each grid was evaluated from the calculated concentration in each medium. The spatial distribution of the heavily polluted area was clarified. These results, combined with demographical and epidemiological data, must be an essential information for risk management of chemical substances such as PCDDs/PCDFs.

Fig.1. Multi-grid and multi-media fate model for the exposure assessment

1)	H. Higashino: Exposure Assessment of Polychlorinated Dibenzo-p-dioxines and Polychlorinated Dibenzofurans by Multi-grid / Multi-media Fate Model, SETAC 19th Annual Meeting, 1998. 11.

National Institute for Resources and Environment