Disinfection byproducts (DBPs) are generated when disinfectants such as chlorine, ozone, chloramine, or chlorine dioxide, react with natural organic matter and/or bromide/iodide present in source waters, and they may pose health risks. Despite intense research carried out in this field, more than 50% of the total organic halogens formed during water disinfection still remain unidentified. Additionally, iodinated DBPs have been found not only in naturally iodide containing waters disinfected, but also in treated source waters where iodide concentration was very low. Thus, other potential sources of iodine, such as iodinated X-ray contrast media used for medical imaging are being explored.The estimated toxicological potency of individual or defined mixtures of DBPs does not account for the magnitude of effects reported in the positive epidemiologic studies, suggesting the need for toxicological evaluation of whole DBP mixtures, including the unidentified DBPs. This problem was addressed by a multi-disciplinary team of researchers from the U.S. EPA in a project known as the “Four Lab Study”, in which toxicological effects of complex DBPs mixtures generated under drinking water chlorination and ozonation/postchlorination scenarios were evaluated.Chloramination of water has been observed to increase the formation of highly cytotoxic and genotoxic iodinated DBPs, nitrosodimethylamine and other nitrosamines; to release solubilised lead in drinking water distribution systems, and to produce skin rashes, respiratory effects, and digestive effects in the population.In this context, the proposal ChE-WADISBYPRO aims to produce and chemically characterize water concentrates of chloramine-derived DBPs mixtures that are suitable to be used in toxicity studies to evaluate the environmental and public health risk of drinking water chloramination, and to investigate the formation of iodo-DBPs from iodinated X-ray contrast media.