Assessing the Risk Associated with Increasing Bromide in Drinking Water Sources in the Monongahela River, Pennsylvania

Bromide concentrations increased significantly in the Monongahela River in Pennsylvania in 2010–2011. These increases led to increases in trihalomethane (THM) and haloacetic acid (HAA) and increased bromination of these disinfection by-products (DBPs) in drinking water at plants on the Monongahela River. This study presents a statistical simulation model to evaluate the effect of the increasing source-water bromide on THM formation and speciation and analyzes the changing risks (by using cancer slope factors) in treated water from 2010 to 2012. Even very low bromide concentrations were associated with increased cancer risk from THM4. HAA9 increased with increasing source-water bromide as well, but the bromination factors of regulated HAA5 decreased. Increasing source-water bromide in the Monongahela River favored bromine incorporation in THM4 rather than HAA9. Collection and analysis of bromide and THM and HAA data for the development of similar bromination factor regression analysis and human health risk assessment for regionally relevant elevated bromide in source water can be used in other areas experiencing or expecting similar source-water changes.