Procedure for Estimating 2, 3, 7, 8 -TCDD/TCDF Concentrations in River Water and Fish and Estimating Potential Impacts to Humans, 1990 Environmental Conference Proceedings

In the United States it is likely that in the next few years dioxin discharges will become regulated under the National Pollutant Discharge Elimination System program. This paper presents a procedure to predict the concentrations of 2,3,7,8-TCDD/TCDF in river water and fish and to estimate potential impacts to human health. The procedure consists of three parts.

The first part is a continuous simulation dynamic model that predicts daily values of 2,3,7,8-TCDD/TCDF dissolved in the water column and sorbed to suspended organic material in rivers. Input parameters for the procedure are site-specific including river flow, effluent flow, and effluent 2,3.7.8-TCDD/TCDF concentration. The procedure incorporates the ability to fill in missing river flow data using a Markov data synthesis technique, and generate effluent flow and dioxin concentration using a Monte Carlo simulator.

The second part of the procedure simulates the processes that govern the bioaccumulation of 2,3,7,8-TCDD/TCDF in fish . The procedure accounts for uptake of TCDD in fish from water and from the food chain. Bioaccumulation is not assumed to be a steady-state process, but rather it is allowed to vary with fluctuating dioxin and furan concentrations in the environment. Input parameters to the procedure allow for site-specific fish community structure and species-specific metabolic attributes to be considered including: distribution/migration, size, ration, assimilation efficiency, uptake and depuration rates, lipid content and growth rate.

The third part of the procedure estimates potential human exposures and risks based upon recent scientific data and site-specific information. Potential exposures and risks are evaluated for people using the river for swimming and drinking water, eating fish from the river and consuming mother’s milk. The procedure allows the flexibility for the user to use different dose-response models and different site-specific exposure assumptions.