Nearly 54% of the American population drink bottled water.1 As they pick up packages of plastic-wrapped bottles off the shelf, they may believe the water within is cleansed of toxic chemicals, free of bacteria, and enhanced with minerals. In truth, bottled water is just as likely to have the same level of harmful chemicals as that of tap water, contain between 20,000 to 200,000 bacterial cells, and lack any beneficial minerals depending on water source.2
As sales of bottled water increase, consumption of tap water decreases.3 Since 1999, the average world consumption of bottled water has increased by 7% each year based on annual per capita,4 now surpassing the sales of milk and beer.5 This growing habit is costly to both the wallet and environment. Companies price bottled water 500 to 1,000 times higher than tap water on average,4 and producing one bottle of water requires 1,000 to 2,000 times more energy than producing the same amount of tap water—in addition to producing plastic waste.5 Are these increased costs justified by the belief that bottled water is safer or cleaner than tap water? In reality, that perception is a marketing myth.
Contrary to popular belief, bottled water is held under lower safety standards than tap water is. There are two different groups regulating drinking water: the Food and Drug Administration (FDA) oversees bottled water and the Environmental Protection Agency (EPA) regulates tap water. In setting health standards, the FDA follows the footsteps of the EPA. The EPA is the first to set limits on dangerous chemicals, biological wastes, pesticides, and microbial organisms in tap water, and the FDA then adopts those limits for bottled water. As a result, regulations on bottled water are no stricter than those on tap water. In fact, they are often weaker. Table 1 lists health standards that differ between bottled and tap water; bottled water only has stricter limits on copper, fluoride, and lead.
The higher lead level of 15 parts per billion (ppb) in tap water allowed by the EPA—three times the limit for bottled water—may alarm some, but research indicates lead exposure at 15 ppb does not elevate blood lead levels in most adults. When the FDA followed suit to establish a lead limit in bottled water, it lowered the limit to 5 ppb because the majority of bottled water manufacturers could reasonably reach that level.6 Bottled water does not need to travel through pipes made of lead, so a stricter limit is sensible and could only be beneficial.
Unfortunately, FDA standards are poorly enforced. Water that is bottled and sold within the same state is not covered by FDA rules: an estimated 60-70% of bottled water sold in the United States meet the criteria of being intrastate commerce and thus are only regulated by the state.6 A survey revealed that most states spend few, if any, resources policing bottled water, so compliance with standards for more than half of the bottled water on grocery shelves is discretionary.6 With overall weaker health standards and lax enforcement of regulation, bottled water is not obligated to be safer than tap water. How does the quality of bottled and tap water compare in reality? Examination reveals differences in their mineral content and microbial content that impacts personal health.
In terms of mineral composition, the amount of mineral content in bottled and tap water largely depends on source and treatment. Bottled water can be designated as spring, mineral, or purified. Spring water, including brands such as Ozarka® and Arrowhead®, originate from surface springs with water flowing naturally from underground supplies. Mineral water is simply spring water with at least 250 parts per million (ppm) of dissolved minerals such as salts and metals.3 Purified water brands such as Aquafina® and Dasani® take water from either underground or tap water sources and filter it to remove all minerals.
Tap water is more simply categorized as being sourced from surface water or ground water. Surface water refers to lakes, rivers, or oceans, while ground water describes any reservoir located beneath the earth's surface. For example, most of the tap water in Houston, Texas originates from a single surface water source.3 The source of any drinking water affects which minerals ultimately remain in the drinking water.
Three specific minerals important for a healthy body are calcium, magnesium, and sodium. Adequate calcium intake is important to maintain and restore bone strength for the young and to prevent osteoporosis in the old. Insufficient consumption of magnesium has been associated with heart disease including arrhythmias and sudden death.3 On the other hand, overly high sodium intake is well associated with high blood pressure and death from heart disease.7 The intake of all three of these minerals can be ensured by drinking water high in calcium, high in magnesium, and low in sodium. In fact, magnesium in water is absorbed approximately 30% faster than magnesium in food.3
A comparative study in 2004 examined these three minerals in bottled and tap water across major U.S. regions. It concluded that drinking two liters per day of tap groundwater water in certain regions or bottled mineral water of certain brands can significantly supplement a person’s daily intake of calcium and magnesium (Table 2).3 To obtain mineral data, the study contacted tap water authorities in 21 different cities spanning the U.S. and obtained published data for 37 North American brands of commercial bottled water. While tap water sources showed wide variations in calcium, magnesium and sodium content, mineral levels of bottled water were more consistent from category to category. In general, tap water from groundwater sources had higher levels of calcium and magnesium than those from surface water sources. High levels of calcium correlated with high levels of magnesium, while sodium levels varied more independently. Out of 12 states, water mineral levels were highest in Arizona, California, Indiana, and Texas. In half of the sources from those states, two liters of tap water allow adults to fulfill between 8 - 16% of calcium and 6 - 31% of magnesium daily recommended intake (DRI). Additionally, more than 90% of all tap water sources contained less than 5% of sodium DRI in two liters.
Amongst the bottled waters, spring water consistently contained low levels of all three minerals, while mineral waters contained relatively high levels of all three minerals (Table 2). Ozarka® spring water, produced in Texas, provides less than 2% of the three minerals' DRIs. In contrast, one liter of Mendocino® mineral water supplies 30% of the calcium and magnesium DRIs in women, and one liter of Vichy Springs® mineral water provides more than 33% of the recommended maximum sodium DRI. Based on these percentages, drinking bottled “mineral” as well as tap water from groundwater sources in certain cities can supplement food intake to fulfil calcium and magnesium DRIs.
Despite labels depicting pristine lakes and mountains, bottled drinking water nearly always contains living microorganisms. In general, processing drinking water serves to make the water safe—not necessarily sterile. The FDA and EPA only regulate bottled and tap water for coliform bacteria, which are independently harmless but indicate the presence of other disease-causing organisms.1 E. coli are an example of coliform bacteria that reside in the human and animal intestines and are widely present in drinking water.8 The total amount of microorganisms in water is often measured by incubating and counting the colony forming units (CFU), or bacteria that develop into colonies. Water with under 100 CFU/mL indicates microbial safety, while counts from 100-500 CFU/mL are questionable.8
In 2000, a research group compared the microbial content of bottled and tap water by obtaining samples from the four tap water processing plants in Cleveland, Ohio and 57 samples of bottled water from a number of stores.9 The bottled water samples included products classified as spring, artesian, purified, and distilled. Bacteria levels in the bottled waters ranged from 0.01 to 4,900 CFU/mL, while the tap water samples varied from 0.2 to 2.7 CFU/mL.9 More specifically, 15 bottled water samples contained at least 10 times as much bacteria as the tap water average, three bottled water samples contained about the same amount of bacteria, and 39 bottled water samples possessed less bacteria. As shown in Figure 1, one-fourth of the samples of bottled water, mainly spring and artesian water, had more bacteria than tap water, demonstrating that bottled water is not reliably more clean of bacteria than tap water. The bacteria in both bottled and tap water can cause gastrointestinal discomfort or illness.10
What is the Healthiest and Cleanest Water to Drink?
Since bottled water and tap waters contain varying levels of microbes, clean water is most reliably obtained by disinfecting tap water with commercially available water purifiers. Most purifiers also act as filters to remove chlorine, its byproducts, and other harmful chemicals that accumulate in tap water. However, chemical-removing filters will also remove any calcium and magnesium present as well, so purified tap water loses its mineral benefits. The loss of aqueous mineral intake can be overcome by eating foods rich in calcium and magnesium; maintaining mineral DRIs will result in a better level of health and energy. Bottled water is not guaranteed to be cleaner than tap water, so drinking properly filtered tap water may be the most economic and health way for hydration.
- Rosenberg, F. A. Clin. Microbiol. Newsl. 2003, 25, 41–44.
- Hammes, F. Drinking water microbiology: from understanding to applications; Eawag News: Duebendorf, Switzerland, 2011.
- Azoulay, A. et al. J. J. Gen. Intern. Med. 2001, 16, 168–175.
- Ferrier, C. AMBIO 2001, 30, 118–119.
- Gleick, P. H.; Cooley, H. S. Environ. Res. Lett. 2009, 4, 014009.
- Olson, E. D. et al. Bottled Water: Pure Drink or Pure Hype?; NRDC: New York, 1999.
- Chobanian, A. V; Hill, M. Hypertension 2000, 35, 858–863.
- Edberg, S. C. et al. J. J. Appl. Microbiol. 2000, 88, 106S–116S.
- Lalumandier, J. A.; Ayers, L. W. Arch. Fam. Med. 2000, 9, 246–250.
- Payment, P. et al. Water Sci. Technol. 1993, 27, 137–143