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Safe Water Monday


What are the differences between tap water and bottled water? Is one safer or healthier than the other?

Nearly all drinking water may contain small amounts of some contaminants, either good (such as minerals) or bad (pesticides, microbes). The Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA) set standards and regulations regarding contaminant levels that must be met for tap water and bottled water, respectively.

In order to meet these standards, most community suppliers of tap water must treat the water via a process that includes pH adjustment, flocculation, sedimentation, filtration, disinfection (usually with chlorine, in a process that was optimized by Johns Hopkins legend Abel Wolman), and fluoridation (in many communities).

In addition to treatment, tap water sources overseen by the EPA must send annual reports to the public, known as consumer confidence reports (CCRs). These reports detail the levels of contaminants that have been detected in the water and compares them with national standards. Individuals with compromised immune systems or who are concerned about the levels reported in their CCR may have their household tap water tested by their local health department or an independent lab. Point-of-use filters, ranging from carbon filters to reverse osmosis systems, can further treat the water to meet individuals' needs or taste preferences. If you do choose filtration, however, be sure to closely follow the manufacturer's directions in order to prevent contamination by bacteria or other harmful substances.

According to the EPA, bottled water is even more variable than tap water when it comes to treatment. While technically bottled water must meet FDA regulations for contaminants, the level that bottled water is treated may be more, less, or even the same as tap water. Therefore, you may be paying between 240 and 10,000 times as much money for the same volume and quality of water, according to the National Resources Defense Council.

One major difference in the treatment of bottled water, however, is lack of fluoridation. While excessive fluoride exposure (a concern for people living in areas of high natural fluoride levels) can be harmful to young children, fluoridation has been proven an effective way to prevent cavities and reduce tooth decay in the community.

Kellogg Schwab, PhD, director of the Bloomberg School's Center for Water and Health, is a self-proclaimed "pro-tap" supporter, “because potable tap water enabled the U.S. to dramatically decrease disease burden and allows us to brush our teeth in ignorant bliss.”

Individuals who obtain their water from non-community/private sources, such as ground water wells, should also know that these sources are not regulated for contaminants. Wells should be checked regularly for safety and, if needed, treated.

To learn about drinking water quality in your local area, visit For more information on fluoridation, go to For a guide to bottled water, check out  

Every Monday, the Johns Hopkins Healthy Monday Project, part of the Johns Hopkins Center for a Livable Future, offers tips for preventing disease and injury, and maintaining a healthy lifestyle. Check back each week for new tips or visit our archive.