Produced water is the largest waste generated from the production phase of oil and gas wells. Analysis of potential environmental risks from produced water in Atlantic Canada is conducted using a developed contaminant dispersion model and Monte Carlo approach. Specifically, a numerical method, POM-RW model is developed to examine the fate and transport of toxic components of produced water effluent at a regional spatial scale, on the basis of an integration of the Princeton Ocean Model (POM) and a Random Walk (RW) simulation of pollutant dispersion. Field validation is conducted for both current field simulation and pollutant concentration prediction. Results from the integrated risk assessment approach reveal that adverse effects on the aquatic life associated with Pb concentration may occur towards its depleted stage of an oil platform.