Predicting national exposure to a point source chemical: Japan and endocrine disruption as an example.

The predicted aquatic estrogen concentrations for the whole of England and Japan were determined and compared using population and flow data. The overall value for English surface waters was 0.9 ng/L estradiol equivalents (EEQ) compared to 0.1 ng/L overall for Japan. Available dilution of sewage effluent was considered to be more important than contraceptive pill usage in this relative risk. A national survey of Japanese rivers using the yeast estrogen assay (YES) gave a median value of 0.27 ng/L EEQ which, while higher than that predicted, confirmed an overall low endocrine disruption risk. Using local population and flow data for 27 separate catchments, the predicted EEQ and measured EEQ (YES) values compared well, confirming the national picture that endocrine disruption would not be a widespread phenomena in Japan. Simple predictions based on population and flow can give an appropriate "ball park" value for catchments and even nations for concentrations of polar organic contaminants which have a majority human origin.