EWG Investigation | U.S. Tap Water Quality Database

Health Limit Exceeded
• Placeholder text

Legal Limit
• EPA set legal limit which balances health concerns and treatment costs

Tier 3 Control - past mining and drilling
• Closed or abandoned mines/plans/notices
• Mineral rich land that has been titled to mining interests (mining patents)
• Formerly drilled and pumped oil & gas Leases

EWG INVESTIGATION

Findings

About The Data

News Release

EWG Statement, 03/10/2008

EPA Programs Leading to Testing or Regulation of Unregulated Contaminants

Safe Drinking Water Act programs that require water suppliers to test for unregulated contaminants, and for the Agency to assess the need for safety standards, have targeted just a fraction of the many hundreds of unregulated contaminants that scientists and water utilities have found in tap water supplies.

EPA stores data from these programs in their National Contaminant Occurrence Database (NCOD), which is not a comprehensive, national database of tap water quality, but is instead a repository for EPA programs that cover only a select fraction of tap water contaminants. When EPA compiled tap water testing data for 16 states (for testing prior to 1997, in this case), the Agency called it the "largest compliance monitoring data set compiled to date by EPA." For its two most significant program to target unregulated contaminants, EPA has compiled just 406,000 contaminant test results for 27 contaminants, based on EWG's analysis of the Agency's NCOD. In contrast, state water offices provided EWG with 22 million tap water quality tests for 260 contaminants. Without national data, the Agency is forced to make decisions on tap water safety standards based on only partial information. EPA programs that have targeted unregulated contaminants, most of which generated data contained in the Agency's National Contaminant Occurrence Database, are summarized below.

Unregulated Contaminant Monitoring Regulation (UCMR) 2.
Test period: 2007-2010. Chemicals tested in tap water: 26, including 11 for full monitoring; 15 in limited screening studies. Utilities included in program: for the "full monitoring" list of 11 contaminants — all utilities serving 10,000 people or more (approximately 3,500 utilities) and 800 small systems serving 10,000 people or fewer; for the "limiting screening" list of 15 chemicals — 120 utilities serving 10,000 people or more, and 800 small systems serving 10,000 people or fewer.

Disinfection by-product National Occurrence Study (EPA 2002). Chemicals tested in tap water and included in analysis: 50 high priority disinfection by-products; disinfection by-products from the Information Collection Rule and regulated disinfection by-products (24). Targeted 12 utilities sampled quarterly. Test period: 2000-2002.

Unregulated Contaminant Monitoring Regulation (UCMR) 1.
Test period: 2001-2005. Chemicals tested in tap water: 28, including 12 for full monitoring; 16 in limited screening studies; 9 with no test method available slated for future rounds. Utilities included in program: for the "full monitoring" list of 12 contaminants - all utilities serving 10,000 people or more (approximately 3,500 utilities) and 800 small systems serving 10,000 people or fewer; for the "limiting screening" list of 9M chemicals — 120 utilities serving 10,000 people or more, and 800 small systems serving 10,000 people or fewer.

Information Collection Rule (ICR). Test period: July 1997 to December 1998. Utilities included in program: 296 public water systems each serving at least 100,000 people. Chemicals tested: 17.

Contaminant Candidate List (CCL). Safe Drinking Water Act directs EPA to select at least five contaminants for CCL every 5 years (beginning in April 2001) to determine if the establishment of enforceable safety limits (NPDWRs, or National Primary Drinking Water Regulations, including MCLs) would reduce risks. After first deadline, EPA announced a decision that no new health standards were necessary for 8 chemicals considered. The Agency is in the second round of determinations now, called the CCL2.

Unregulated Contaminant Monitoring (UCM), Round 2.
Chemicals tested in tap water: 48. Test period: 1993-1997. Utilities included in program: 41% of all public water systems, representing 34% of the population drinking public tap water. States included: 35.

Unregulated Contaminant Monitoring (UCM), Round 1.
Chemicals tested in tap water: 62. Test period: 1988-1992. Utilities included in program: 40% of all public water systems, representing 51% of the population drinking public tap water. States included: 40.