This story is part of a special series that explores the global water crisis. For more clean water news, photos, and information, visit National Geographic's Freshwater Web site.
As the U.S. taste for bottled water grows, environmentalists have been trying to sell people on good old-fashioned—and free—tap water.
But tap water's place in schools is thorny, since some experts say children should actually be drinking more bottled water to head off two stubborn health threats: obesity due to sugary drinks and lead poisoning.
"If children go from sugary beverages to bottled water, you get a benefit to public health, but not so much the environment," said Kelly Brownell, director of the Rudd Center for Food Policy and Obesity at Yale University.
"If they go from sugar beverages to [clean] tap water, you get a public health home run and environmental home run."
Bottled water is a drain on the environment: The U.S. public goes through about 50 billion water bottles a year, and most of those plastic containers are not recycled, according to Elizabeth Royte's 2008 book Bottlemania: How Water Went on Sale and Why We Bought It. Transporting the bottles and keeping them cold also burns fossil fuels, which give off greenhouse gases.
Groundwater pumping by bottled-water companies also draws heavily on underground aquifers and harms watersheds, according to the environmental nonprofit the Sierra Club. And a 2008 investigation by the nonprofit Environmental Working Group found some bottled water is sullied with untested industrial chemicals, and may not necessarily be cleaner than tap water.
(Related: "Bottled Water Isn't Healthier Than Tap, Report Reveals.")
But switching to tap water could be a bad idea in some schools where the risk of lead contamination from old pipes—known to affect physical and mental development—is high, particularly in large urban areas such as Chicago, Los Angeles, and Washington, D.C.
For instance in September 2009, the Associated Press published a nationwide investigation showing that the drinking water in schools in 27 states is contaminated with lead and other toxic substances from lead-soldered pipes generally installed before 1985.
Schools that rely on their own wells are subject to regular testing by the U.S. Environmental Protection Agency (EPA). But the agency does not regulate drinking-water quality for the rest of the nation’s schools, which get their water from local utilities.
Most school districts do not test their water because of the costs associated with lead remediation, said Marc Edwards, a civil engineer at Virginia Tech.
"Even when we offer to do the analysis for free, the majority of schools don't want to know," Edwards said.
But some solutions are much less costly than replacing a whole pipe system, he said. Those range from putting filters on taps to remove lead, to flushing water fountains after a period of stagnation.
Still, for some school districts, the most cost-effective measure may be providing kids with bottled water.
In 2007, Baltimore City public schools switched their entire system to bottled water after a study of 84 randomly selected water fountains found 10 with lead levels high than the EPA's cutoff of 20 parts per billion. The school district decided it would be cheaper to provide bottled water than testing and remediation efforts.
Edwards applauds Baltimore's decision.
"I’m a huge proponent of tap water, but if your child going to one of schools where pieces of lead are falling into the tap water on a random basis, that risk pales in comparison to the small cost of bottled water."
Margo Wootan, director of nutrition for the Washington, D.C.-based Center for Science in the Public Interest (CSPI), added that environmental groups that have demonized bottled water should refocus their campaigns on all bottled beverages, including soda.
"Environmentalists place a higher burden on people who drink water instead of soda, and that isn’t fair," Wootan said.
School beverages, particularly sugar-laden soda and sports drinks sold in vending machines, have come under increasing fire from nutrition-advocacy groups such as CSPI.
Obesity rates among children aged 6 to 11 have more than doubled in the past 20 years, according to the U.S. Centers for Disease Control and Prevention. A 2006 study by Harvard nutritionists found sugar-sweetened beverage consumption is linked to higher body weight among adolescents.
"Soda in schools has been such a huge problem for the last couple of decades, and getting rid of sugar-sweetened beverages and shifting to bottled water should be a top priority," Wootan said.
The School Nutrition Association is also advocating for the elimination of all sugar-sweetened beverages from all schools when Congress takes up the reauthorization of the Child Nutrition Act in March 2010.
Low-fat milk, 100-percent juices, and bottled water are the new recommended beverages for school meal programs and vending machines.
But other health experts intend to keep fighting for tap water.
"There's more demand for bottled water now in schools, and the beverage industry says they have public health in mind," Yale's Brownell said. "But we're hoping to do a big campaign to encourage consumption of tap water instead."