AN ECOLOGICAL RISK ASSESSMENT FOR THE USE OF THE BIOCIDE, DIBROMONITRILOPROPIONAMIDE (DBNPA), IN INDUSTRIAL COOLING SYSTEMS

A tiered approach was employed to determine risks posed to aquatic org anisms exposed to dibromonitrilopropionamide (DBNPA). Tier one assessm ents used conservative exposure and toxicity data and indicated that p otential toxicity warranted a more rigorous risk assessment. Tier two used discharge and stream dow data to develop a probabilistic model of DBNPA concentrations reaching the stream. Predicted 90th percentile i n-stream DBNPA concentrations were compared to all available toxicity data for aquatic organisms at several different trophic levels. The EC 10 for one organism was similar to the calculated 90th percentile of D BNPA concentrations in streams. Using the complete EC10 data set and c omparing the 10th percentile EC10 with the 90th percentile environment al concentration, DBNPA did not pose a measurable risk to the aquatic ecosystem.