Water Resources Research Act Program

Principal Investigators: Howard Weinberg, Kirsten Studer

Abstract: Due to the absence of or limited regulations on medical discharge to the sanitary sewer, many pharmaceutically active agents from hospitals and patients reach wastewater treatment plants which may not be able to adequately remove them. Among these are iodinated-contrasting agents which several large hospitals and many medical facilities across the state administer to patients for soft tissue imaging. The contrast media are applied at high doses and are eliminated without metabolization of the parent compound through the urine and feces. Previous studies have observed evidence that these agents break down in wastewaters, releasing iodide that could appear in surface waters. Fuge and Johnson reported that US rivers and freshwater lakes show a range in iodide levels of 0.01 to 73.3 μg/L, but with little indication of high natural levels of iodide in North Carolina surface waters. One specific occurrence study of twenty-three cities observed significant iodinated disinfection byproducts (DBPs) in drinking waters whose sources contained low iodide concentrations that were determined to be a result of medical imaging compounds reacting with drinking water disinfectant. Epidemiological studies have indicated a weak correlation between chlorinated drinking water exposure and various types of human cancer, with bladder, colon, and rectal cancers being the primary disease endpoints, and the health implications focusing on DBPs. From the known byproducts, the non-regulated iodinated DBPs have been shown to have an increased toxicity in comparison to other DBPs. Iodoacids are a subset of haloacetic acids (HAA) but are not currently regulated by the US Environmental Protection Agency (EPA). According to Plewa et al., iodinated DBPs are over 250 times more cytotoxic than the regulated chloroacetic acid. Due to the increased toxicity of iodinated DBPs, the US EPA has identified these compounds, along with brominated species, as DBPs of emerging toxicological interest.