People who buy bottled water for its perceived purity may not be getting what they're paying for. They're most likely not getting adequate fluoride either, according to researchers at Case Western Reserve University and Ohio State University.
In a study published in the March issue of the "Archives of Family Medicine," a journal of the American Medical Association, researchers compared the bacterial content and fluoride levels of 57 samples of bottled water with tap water from each of Cleveland's four water treatment plants.
"Only three bottled waters ... had fluoride levels within the range recommended by the Ohio Environmental Protection Agency," according to James Lalumandier, a CWRU assistant professor of dentistry, and Leona W. Ayers of OSU's College of Medicine and Public Health. The other 54 bottles fell short of the recommended range of 0.80 to 1.30 milligrams of fluoride per liter.
All Cleveland tap water samples, however, were not only within the accepted range but also scored very near the optimal level of 1.00 milligrams per liter.
Bacterial counts in the four tap water samples varied only slightly, from 0.2 to 2.7 bacterial colonies per milliliter. In the bottled water, bacterial counts ranged from less than 0.01 to 4,900 colonies per milliliter. Six bottled waters had bacteria counts of 1,500 to 4,900 colonies per milliliter.
"One of the reasons people choose to drink bottled water instead of tap water is because of the perceived purity of bottled water," the researchers observe, and indeed, 39 samples of bottled water were found to be purer than the tap water. However, 15 samples of bottled water had significantly higher bacteria levels than the tap water. Of these 15, the bacteria counts were more than twice as high as the most contaminated tap water sample and almost 2,000 times higher than the purest tap water sample.
Technicians at the Ohio Department of Health Laboratories in Columbus tested the water samples, which the researchers coded by number to eliminate the potential for bias.
Despite the high bacteria levels in some of the bottled water, all the water tested is safe to drink under government standards, Lalumandier said. Still, he and Ayers conclude, "use of bottled water on the assumption of purity can be misguided."
For Lalumandier, who heads the Department of Community Dentistry at the dental school, the low fluoride content of most bottled water is a significant concern. The use of fluoridated water is a major factor in the prevention of tooth decay in children and adults, he notes. People who rely on bottled water may be at greater risk for tooth decay. According to a survey of 1,000 pediatric patients, 9 percent of the children used bottled water as their primary source of drinking water.
"Children should be considered for prescribed fluoride supplements if they drink bottled water," the researchers recommend. However, since a small percentage of bottled water contains adequate fluoride, children who drink such water should not get supplementary fluoride. That's because excessive ingestion of fluoride during childhood can cause fluorosis, a demineralization of the dental enamel that may result in discolored teeth.
Manufacturers are not required to include fluoride levels on their labels, but the researchers believe they should be. Currently, consumers must either get their water tested or contact the manufacturer for this information. The researchers attempted to contact all 57 manufacturers in their study, but were successful in reaching only 37.
The bottled water industry is one of the fastest-growing businesses in the United States, with annual sales of nearly four billion gallons, Lalumandier and Ayers said.
"Bottled water should be required to meet the same standards for fluoride levels and bacterial content as tap water, as it makes up a significant proportion of the water consumed by the public," they conclude.
Journal
Archives of Family Medicine