Bottled water sold in the United States is not always filtered and is not necessarily cleaner or safer than most tap water, according to a four-year scientific study recently made public by the Natural Resources Defense Council (NRDC). The NRDC's study included testing of more than 1,000 bottles of 103 brands of bottled water. While most of the waters were found to be of high quality, some brands were significantly contaminated. About one-third of the waters tested contained levels of contamination including synthetic organic chemicals, bacteria, and arsenic (at least one sample exceeded allowable limits under either state or bottled water industry standards or guidelines) NRDC's report points out that more than 40% of all bottled water comes from a city water system, just like tap water. The report also shows that 60-70% of all bottled water is exempt from FDA's bottled water standards, because it is bottled and sold within the same state. According to the NRDC, "bottled water companies have used this loophole to avoid complying with basic health standards, such as those that apply to municipally treated tap water."

According to the NRDC study, "even when bottled waters are covered by FDA's specific bottled water standards, those rules are weaker in many ways than EPA rules that apply to big city tap water." City tap water can have no confirmed ecoli or fecal coliform bacteria. FDA bottled water rules include no such prohibition (a certain amount of any type of coliform bacteria is allowed in bottled water). City tap water, from surface water, must be filtered and disinfected. In contrast, there are no federal filtration or disinfection's requirements for bottled water. Most cities using surface water have had to test for Cryptosporidium or Giardia, two common water pathogens, that can cause diarrhea and other intestinal problems, bottled water companies do not have to do this. City tap water must meet standards for certain important toxic or cancer-causing chemicals, such as phthalate (a chemical that can leach from plastic, including plastic bottles); some in the industry persuaded FDA to exempt bottled water from the regulations regarding these chemicals.

City water systems must issue annual "right to know" reports, telling consumers what is in their water. Bottlers successfully killed a "right to know" requirement for bottled water. The Natural Resources Defense Council report concluded that; "Therefore, while much tap water is indeed risky, having compared available data, we conclude that there is no assurance that bottled water is any safer than tap water." The FDA says:"Companies that promote bottled water as being safer than tap water are defrauding the American public." Home water purification is the most economical, convenient, and safest way of producing high quality drinking water for your everyday needs.