The Power of Information

National Drinking Water Database


National Drinking Water Database - Executive Summary

Executive Summary


Since EWG's tap water database was published in December 2009, we have received new water test results from several utilities. The database and our city-by-city water quality rankings will be updated in the near future.

December 2009

Americans have good reason to worry about the safety of the drinking water that flows from their taps, according to the results of a 3-year investigation by the Environmental Working Group (EWG).

EWG assembled an unprecedented database of 20 million drinking water quality tests performed by water utilities since 2004. It reveals a total of 316 contaminants in water supplied to 256 million Americans in 48,000 communities in 45 states. Among the contaminants were 202 chemicals that are not subject to any government regulation or safety standards for drinking water. The U.S. Environmental Protection Agency (EPA) has set enforceable drinking water safety standards for only 114 of the 316 substances detected (EPA 2009b).

pie chart

Source: EWG analysis of water utility test data for 2004-2009 provided to EWG by state drinking water offices. Data includes 20 million water quality tests for 47,677 communities in 45 states and the District of Columbia. Details on EPA-regulated contaminants detected in this study are described in Note 1 below.


For the 114 contaminants that are regulated, EWG's drinking water quality analysis found that utilities achieved 92 percent compliance with EPA's mandatory health standards, demonstrating that utilities can and do comply with regulatory standards when they exist. However, EPA's failure to establish effective source water protection programs and to develop enforceable standards for scores of other contaminants leaves the public at risk.

Using the database, EWG developed a unique online, interactive ranking system to evaluate 100 water utilities that serve cities of more than 250,000 people. The online resource also includes data on household water filtration systems to help consumers who want additional protection decide which types will best serve their needs.

Where the Data Come From

EWG obtained tap water testing data from state water offices, which had collected the results from the utilities in order to enforce state and federal water quality standards. EPA does not maintain its own comprehensive national drinking water quality database. The agency sets safety standards for contaminants based on limited test data gathered from select, representative states and water suppliers. EWG was unable to obtain water test results in electronic form from five states and the District of Columbia. EWG will provide its database upon request to the EPA and state authorities.

The water contamination revealed by EWG's database underestimates the scope of the problem. For 37 percent (17,840) of the 47,677 water systems analyzed by EWG, states' databases contained no records of testing for any unregulated contaminants. EPA's own limited surveillance programs have required testing for just a fraction of the hundreds of unregulated drinking water pollutants identified in peer-reviewed studies.

EPA has set maximum allowable levels in drinking water for 114 pollutants reported in EWG's database. In addition, the government has issued health guidelines for 90 of the 202 unregulated contaminants to provide advice for utilities and consumers. Our analysis found that 87 regulated and 49 unregulated chemicals were detected at least once at levels above these voluntary guidelines. A total of 252 million Americans were supplied at one time or another with water containing contaminants at concentrations above the recommended safety guidelines.

Source: EWG analysis of tap water testing data provided by state agencies. Details on health guidelines used in this study are described in Note 2 below.

Unprotected Source Water Drives Up Treatment Costs

The chemical pollutants identified in EWG's database come from various sources, including: factory farm waste, pesticides, fertilizer and sediment; sewage and urban runoff; industrial chemicals; water treatment and distribution byproducts; and natural processes that produce more contamination as a result of development and deforestation.

By failing to clean up rivers and reservoirs that provide drinking water for hundreds of millions of Americans, EPA and the Congress force water utilities to spend heavily to make contaminated water drinkable. According to industry market studies, drinking water utilities spend more than $4 billion a year on water treatment chemicals alone. Less than one-twentieth that amount is invested in source water protection and pollution prevention, an average of $207 million per year (data for 1997-2008). This includes funds allocated for the management of nonpoint water pollution sources under the Clean Water State Revolving Fund and for source water protection under the Drinking Water State Revolving Fund (EPA 2009l; EPA 2009m; EPA 2009n).

Data sources are described in Note 3 below.


EPA Inaction on Drinking Water Safety

The EPA has not set a new, enforceable drinking water standard since 2001, even though the Safe Drinking Water Act requires EPA to assess the need for standards for at least five new chemicals every five years. Three-fourths of the current standards were set in 1991 and 1992 and have not been updated since.

Since 1996, EPA has reviewed data on toxicity and water pollution for 138 chemicals, but in every case it declined to set a safety standard. EWG's database analysis showed that collectively these chemicals pollute drinking water for more than 111 million Americans.

To their credit, some states require testing for a broader range of chemicals than those specified in federal regulations, and some utilities choose voluntarily to test more extensively than either state and federal regulations require. EWG's analysis of testing rates found that municipal water systems reported testing for more than 250 contaminants in three states (California, New York and Missouri) between 2004 and 2009. Municipal systems in Kentucky, Connecticut and South Dakota, on the other hand, reported testing for 90 or fewer chemical pollutants during the same period.

EWG's recommendations:

Millions of Americans buy bottled water in the mistaken belief that it's safer than tap water, but this is not the answer. Many popular brands are nothing more than bottled tap water, tainted with the same pollutants, and the enormous growth of the bottled water market has bloated the nation's solid waste stream with vast amounts of plastic.

Based on its analysis of the database findings, EWG believes that:

  • EPA should construct and maintain a consumer-accessible national database of tap water quality testing.
  • EPA should greatly expand requirements for testing unregulated contaminants.
  • Federally-mandated Consumer Confidence Reports issued by water utilities rule should disclose all detected contaminants.
  • EPA should set health-protective standards for unregulated chemicals in tap water.
  • Federal programs to protect source water protection should be significantly expanded.
  • Federal laws and policies must be updated to protect vulnerable populations, including pregnant women and children, from chemical pollution of food, the environment and especially drinking water.

Note 1: EPA has set standards for 114 pollutants present in tap water tests analyzed by EWG. These include 108 pollutants regulated under 80 enforceable standards for chemicals or chemical groups (Maximum Contaminant Levels, or MCLs), and 6 pollutants from the 15 for which EPA has established guidelines called National Secondary Drinking Water Regulations (NSDWRs).

Note 2: Health based limits included in this analysis include enforceable drinking water limits (MCLs) as well as governmental, non-enforceable health guidelines, such as Maximum Contaminant Level Goals (MCLGs), lifetime health advisory levels, one-day and ten-day advisory levels to protect children from non-cancer health endpoints, and other government-established health guidelines for tap water contaminants.

Note 3: Data sources for Figure 3 — Cost of water treatment: Over $4 billion spent on drinking water treatment chemicals in the U.S. every year (Frost & Sullivan 2004; Maxwell 2009). According to EPA data for 1997-2008, annual federal funding for drinking water pollution prevention has included: an average of $197 million spent annually under the Clean Water State Revolving Fund; an average of $9.7 million spent annually on wellhead protection projects; and an average of $1 million spent on source water protection under the Drinking Water State Revolving Fund program (EPA 2009l; EPA 2009m; EPA 2009n).