AWWA WQTC62525

The CCL classification process involves three major stages. The first stage identifies chemicals that are present in or have the potential to be present in drinking water, or chemicals that have demonstrated or have potential adverse health effects. Taking into account both the occurrence and adverse health effects data, the second stage narrows the pool of candidates to a preliminary CCL (PCCL). The PCCL is an intermediate step for contaminants that will be scrutinized in more detail in the development of the CCL. The third stage of the process involves analyzing contaminants on the PCCL to develop the CCL. The first two stages of analyses - data evaluation and the screening process are discussed below. The first step in developing the universe of potential drinking water chemical contaminants was to identify and retrieve data sources that have information about occurrence of chemicals in water, a link or pathway to drinking water, and health effects. Using this as the initial criteria, 284 data sources were identified which included hundreds of thousands of chemicals. These sources contained disparate types of data for a variety of chemicals. These data sources were further evaluated to identify the most relevant sources that provided unique data and information on a chemical's potential to occur in drinking water and cause adverse health effects. Assessment factors were developed to prioritize the data sources and identify chemicals to consider in the CCL process. Each source was evaluated for its relevance, completeness, redundancy, and retrievability. Using the assessment factor criteria, 39 data sources were chosen to construct the CCL universe of chemical contaminants. The goals of the second stage are to screen the chemicals from the 39 data sources on a limited set of available data elements representative of health effects and occurrence, and to select contaminants for the PCCL based upon a level of concern. Available data elements that represent health effects include the reference dose (RfD), lowest observed adverse effect levels (LOAEL), lethal dose (LD50), and cancer classifications. The data elements representative of occurrence include: measured values in finished, ambient and source waters, release/use data (lbs/year, number of States), production data (lbs/year), and persistence measures (half-life, biodegradation rates). Utilizing available occurrence and health effects data; U.S. Environmental Protection Agency (USEPA) is examining the impact of several criteria that could be used to select contaminants for inclusion on the PCCL. Includes abstract only.