Overview of the CCL 5 Approach

The development of CCL 5 is based on the existing framework used for the previous Contaminant Candidate List 3 (CCL 3) and its carryover, the Contaminant Candidate List 4 (CCL 4). In developing CCL 5, updates were made to allow EPA to consider a larger number of contaminants, enhance greater transparency in the data being evaluated, and improve more efficiency of transferring of information compiled for CCL to other SDWA processes such as Regulatory Determination and UCMR activities. 

The CCL framework consists of three steps:

Step 1 identifies a broad universe of potential drinking water contaminants, called the CCL 5 Universe. EPA initially considered approximately 23,500 potential chemical and microbial contaminants.

Step 2 applies screening criteria to the CCL 5 universe. EPA identified over 300 contaminants for further evaluation, called the Preliminary CCL 5 (PCCL 5), based on their potential to occur in public water systems and their potential for public health concern.

Step 3 selects contaminants from the PCCL 5 to include on the CCL 5 based on more detailed evaluation of occurrence and health effects and expert judgment. The CCL 5 process concluded with the selection of 66 chemicals, three chemical groups and 12 microbes.