On November 17, 2016, the U.S. Environmental Protection Agency (EPA) published in the Federal Register a final list of contaminants that are currently not subject to any proposed or promulgated national primary drinking water regulation. This list is the Fourth Contaminant Candidate List (CCL 4) published by EPA since the SDWA amendments of 1996. The Final CCL 4 includes 97 chemicals or chemical groups and 12 microbes listed, which can be found here: https://www.federalregister.gov/documents/2016/11/17/2016-27667/drinking-water-contaminant-candidate-list-4-final
and here: https://www.epa.gov/ccl/contaminant-candidate-list-4-ccl-4-0
Manganese, currently listed as a secondary contaminant under the SDWA, has been added to the final CCL 4. The EPA must now determine whether or not to regulate at least five contaminants from the CCL 4 in a separate process called Regulatory Determination 4. EPA will compile and evaluate additional data on the CCL 4 contaminants. The Agency will make regulatory determinations for the CCL 4 contaminants for which there is sufficient health effects and occurrence data and which present the greatest public health concern.