The 1996 Amendments to the Safe Drinking Water Act (SDWA) require that the Environmental Protection Agency (EPA) shall, at least once every six years, review and revise, as appropriate, each National Primary Drinking Water Regulation (NPDWR). The NPDWRs are often referred to as the national drinking water contaminant regulations or drinking water standards. The Six-Year Review process is an assessment of new information on the health effects and national occurrence, and the new capabilities of treatment technologies and laboratory analytical methods for the regulated contaminants. Through this process, EPA determines whether the new information and technical capabilities provide a scientific basis to support a revision of existing regulations that will improve public health protection. This report presents the national contaminant occurrence assessments conducted in support of EPAs second Six-Year Review of NPDWRs. Included are detailed descriptions of the national contaminant occurrence dataset compiled, the data management procedures conducted to develop the national dataset, and the statistical analytical methods employed (using the national dataset) to generate national estimates of regulated contaminant occurrence in public drinking water systems.

Cover title. "October 2009." "EPA-815-B-09-006." Format not distributed to depository libraries.