Clean Drinking Water and How to Get It: Advising Patients

Julia Gargano, PhD


January 28, 2013

Editorial Collaboration

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Hi. I am Dr. Julia Gargano, an epidemiologist at CDC. Thanks for tuning in to this CDC Expert Commentary on Medscape.

Access to clean drinking water is essential for good health and a key component of public health. However, there is a great deal of variation in our drinking water supplies in the United States, and this has implications for your patients' health. Today I will share 3 things that clinicians should think about when talking to patients.

Not all water sources are created equal. Most people in the United States -- about 85% -- are served by public water systems, regulated by the Environmental Protection Agency (EPA). Most people who live in cities rely on water systems that come from surface water sources, such as a rivers or lakes. Surface water must be filtered or treated with a disinfectant.

Chlorine, the most common disinfectant, dissipates quickly and produces small amounts of chemical disinfection byproducts. The levels of these byproducts are regulated because at certain levels they can cause cancer after long-term exposure.

Some water utilities are switching to monochloramine, which does not dissipate as quickly and produces fewer byproducts. Patients should not be concerned about this change. There are no observed health effects with normal or even somewhat high concentrations of monochloramine in drinking water.

Other public water systems use ground water sources, usually wells. Regulations do not require many smaller ground water systems to add a disinfectant.

Not everyone has a public water supply. About 15% of US households, potentially 45 million people, rely on private wells, which are not federally regulated. Private wells are prone to poor construction, operation, and maintenance, and water can be contaminated with a variety of pathogens and chemicals. It's up to individuals to have their well water tested to make sure that it is safe to drink.

Wells should be tested annually, and additional testing is recommended if there are changes in or near the well or if pregnant women, infants, children, or immune-compromised persons are in the household. State or local health departments are good resources for well testing information. Additional information on well water testing is available in the resources listed at the end of this commentary.

Things that make water taste better don't always improve health. Many people choose to drink bottled water instead of tap water because of taste, smell, or health concerns or as a substitute for other beverages. The standards for bottled water are set by the US Food and Drug Administration (FDA) and are based on EPA standards for tap water, so don't assume that bottled water is safer than tap water. The label, an 800 number provided by the company, or the company Website might help you find information about the way your bottled water was treated.

Some patients might have questions about exposure to the endocrine-disrupting chemical bisphenol A (BPA) from water bottles. BPA is not used in commercially produced disposable water bottles, but some reusable water bottles, carboys, and dispensers are made of polycarbonate plastic and may contain BPA. General exposure to BPA at low levels comes from eating food or drinking water stored in containers that have BPA. BPA has been shown to affect the reproductive systems of laboratory animals, although human health effects from BPA at low environmental exposures are unknown.

Some patients might think that using a home water filter, such as a filter pitcher or filtered refrigerator dispenser, protects against contaminants in their water. Most filters, however, only improve water taste and odor. Most aren't designed to protect against pathogens. The insert information on the filter may provide this information.

People with weakened immune systems may want to use treatments that protect against Cryptosporidium, such as reverse osmosis, distillation, or filtration with an absolute 1-µm filter. If such patients choose to use bottled water, they need to make sure it has been treated with one of those methods.

Just because it's safe to drink doesn't mean it's safe for everything. Although our public water supplies are usually safe to drink, tap water is not sterile and not appropriate for some purposes. Please remind your patients not to use tap water when irrigating their sinuses with a neti pot or other device or when rinsing or storing contact lenses.

We tend to take drinking water for granted for a good reason: It generally is safe for drinking by most people, most of the time. Regulations enacted over the last few decades have reduced the risk for outbreaks of disease in treated public water systems. But you and your patients need to be aware of where your water comes from and what it can be safely used for.

Web Resources

General Topics

CDC: Drinking Water

CDC: Drinking Water Publications, Data, & Statistics

CDC: Drinking Water Advocacy, Policy, & Recommendations

EPA: Ground Water and Drinking Water

Diseases and Contaminants

CDC: Water-Related Diseases, Contaminants, and Injuries by Type

CDC: National Biomonitoring Program. Bisphenol A (BPA)

EPA: Drinking Water Contaminants

Water Sources and Testing

CDC: Public Water Systems

CDC: Private Water Systems

CDC: Well Testing

CDC: Commercially Bottled Water

FDA Food

FDA Regulates the Safety of Bottled Water Beverages Including Flavored Water and Nutrient-Added Water Beverages


CDC: Parasites - Cryptosporidium: A Guide to Water Filters

CDC: Naegleria fowleri -- Primary Amebic Meningoencephalitis (PAM)

CDC: Acanthamoeba -- Granulomatous Amebic Encephalitis (GAE); Keratitis -- Microbial Keratitis

EPA: Private Drinking Water Wells

Julia Gargano, PhD, is the Drinking Water Epidemiologist in the Waterborne Disease Prevention Branch in CDC's National Center for Emerging and Zoonotic Infectious Diseases. The Waterborne Disease Prevention Branch oversees the Center's waterborne disease activities, including domestic and international waterborne disease outbreak investigations, national surveillance for cryptosporidiosis and giardiasis, and the national Waterborne Disease and Outbreak Surveillance System.

Dr. Gargano's current research includes development of a national burden of waterborne disease estimate and a prospective epidemiologic study to evaluate health effects from low-pressure events in drinking water distribution systems. Dr. Gargano received her PhD in Epidemiology from Michigan State University in 2009. She joined the Centers for Disease Control and Prevention in 2009 and served in CDC's Epidemic Intelligence Service from 2009 to 2011.