How Safe Is Your Drinking Water?
Corrected and clarified 7/26/07. A previous version of this story misspelled the name of Greg Kail of the American Water Works Association. It also may have implied that containers for bottled water can leach certain chemicals that such bottles don't necessarily contain.
A worrisome study released yesterday about the quality of Washington, D.C.,'s tap water highlights the fact that public drinking water—the life-sustaining substance that experts recommend drinking eight glasses of each day—can come through the tap loaded with a slew of contaminants.
But drinking bottled water may not be a perfect solution either, some scientists say.
In Washington, where high lead levels have been in the public eye for several years, the latest concern stems from the detection of high levels of chemicals produced during the disinfection process. According to the study, which was conducted by the nonprofit Environmental Working Group, the disinfectant chlorine reacts with organic material in water to produce potentially harmful byproducts, including compounds known as trihalomethanes and haloacetic acids.
Experts on drinking water quality say chlorination byproducts are hardly the only safety concern in tap water. Other water quality issues that have cropped up in various municipal water supplies include microbes and parasites that cause gastrointestinal distress and occasionally severe complications, poisonous elements such as lead and arsenic, and various potential carcinogens.
Problems like these explain why many consumers turn to bottled water. A recent Gallup Poll, commissioned by the Environmental Protection Agency, showed that 1 person in 5 drinks only bottled water and that almost 2 in 5 use a filtering device to treat their tap water. When Gallup asked these people why they bought bottled water or filtered their water, 33 percent cited health-related reasons. That slightly exceeded the proportion of people—28 percent—who did so because of differences in taste.
The sense of added security comes with a high price tag. Greg Kail, spokesperson for the American Water Works Association, says that the $1.50 or so that a typical 20-ounce bottle of water costs will generally pay for about 1,000 gallons of municipal water. "That's enough to fill that same bottle every day for 13 years," he notes. And filtration devices can cost thousands of dollars.
But is bottled water really any safer? The unsatisfying answer is that nobody seems to know for sure.
"There is uncertainty about both tap and bottled water," says Ronnie Levin, an EPA expert on water quality and a visiting scientist at Harvard University. "It really comes down to your comfort level."
While people may assume bottled water is safer, it's also subject to unique hazards, according to experts. "Bottled water companies have been selling the myth that bottled water is safer," says Eric Goldstein of the National Resources Defense Council, an environmental group. But regulation of bottling practices can be spotty, he says. Moreover, some research shows that the bottles themselves may pose health risks, and—since some bottled water is simply processed and repackaged municipal water—problems inherent in city water can be passed along, depending on the quality of the purification processes.
"The purification process may or may not be excellent," says Levin. Although bottling companies may have good filtration equipment, there's no guarantee that they clean their filters or promptly fix filters that break, she says. Indeed, one study published in the Archives of Family Medicine conducted by researchers at Case Western Reserve University found that 15 of 39 bottled water samples had bacterial counts nearly twice as high as Cleveland tap water. The highest had more than 2,000 times the amount of bacteria found in the clearest tap water.
Bottled water critics also point out that plastics can leach chemicals—including such tongue-twisters as phthalates and bisphenol A—that disrupt hormones and seem to cause problems such as infertility and cancer in lab animals. However, according to the National Association for PET Container Resources (NAPCOR), containers made of polyethylene terephthalate (PET), the type that most bottled water is sold in, contain neither bisphenol A nor the phthalates that critics worry about. (For more information, see "The Safety of PET Bottles.") Nevertheless, Levin is sufficiently concerned about chemical hazards that she tries to avoid foods and liquids that have been stored in plastic containers.
But most experts say that, in this country, both tap and bottled water are remarkably safe. About 12 times as many Americans are killed by lightning each year as are killed by outbreaks of water-borne diseases.
"In general, there is not a significant difference in the health risk between bottled and tap water," says Marc Edwards, a drinking water expert at Virginia Tech. But he notes that in certain situations—if a community's tap water is known to have high lead levels, for example, or a person has an immune system too compromised to fend off waterborne pathogens—bottled water is probably the better bet.