It's rough enough that the millions of Americans who buy bottled water are paying for something that used to basically be free. But even harder to stomach is the message that comes on the bottle: Like milk and eggs, water now "expires."

Most commercially produced water comes stamped with expiration dates -- typically within two years of when it was bottled. On most Poland Spring bottles there are tiny, white letters advising consumers to drink up within two years. Most Aquafina bottles sport two-year expiration warnings on their caps. In general, the dates on bottled water include the prefix "EXP," meaning "expires." Fiji brand water has a slightly different approach: Its bottles say "Best by" followed by the date. Coca-Cola Inc. puts a one-year expiration date on its Dasani brand water.

The message that water has a shelf life has been further amplified in the wake of Sept. 11. The U.S. Department of Homeland Security urges people to stockpile water in their disaster-preparedness kits. On its web site (www.ready.gov), it instructs people to change their stored water every six months.

The American Red Cross also advises people via its Web site to replace their stored water every six months. But when contacted, the organization's manager of disaster education, Rocky Lopes, says people should replace their bottled water before its expiration date. "The water should be replaced if the manufacturer determines there is a reason for it," he says.

But does water really spoil? Despite the labels reminding consumers to drink up, there is virtually no evidence that drinking water beyond the expiration date has any health impact at all. The Food and Drug Administration considers bottled water to have an "indefinite shelf life." Even the bottled-water industry is hard-pressed to justify the labels.

"There's no real rationale," says Jane Lazgin, a spokeswoman for Nestle Waters North America Inc., a division of Nestle SA that bottles brands including Poland Spring and Ice Mountain, and imports European waters such as Perrier and Vittel. The practice "is not health-based," she adds.

Still, some shoppers are heeding these directives. If bottled water is past its expiration date, "there's probably something wrong with it," says John Bohan, a 39-year-old father of three in Los Angeles who drinks only bottled or filtered water. "I would drink bad tap water over post-dated bottled water."

Expiration dates are just one example of how shifting tastes and successful marketing have complicated what was once one of life's simpler acts -- drinking water. This year, for the first time, Americans are expected to buy more bottled water than beer or coffee. Sales of bottled water reached $7.7 billion in 2002, up 12% from 2001, according to Beverage Marketing Corp., a New York-based consulting company. Even dogs now have bottled-water options -- K9 Water Co. makes chicken- and beef-flavored waters.

Store shelves are filled with a baffling array of options, from "spring water" and "artesian water" to "purified water" and "drinking water." (The latter is often industry code for filtered tap water.) And, for all the popularity of bottled water, there is little evidence that it's any better for you than what flows from the faucet.

Some bottled water makers say that they use expiration dates for taste, and not health reasons. A Coca-Cola spokeswoman, Susan McDermott, says the company has done research on its own Dasani brand showing that the taste of its bottled water changes after its one-year expiration date. But, she adds: "It is probably not something the average person will notice." Manufacturers also say most people drink their water well short of the industry average two-year mark.

The government says that the recommendation on the Department of Homeland Security Web site is really directed at people who bottle their own tap water. Unsealed containers could allow bacteria or other contaminants into the water that could multiply, experts say. It's unclear, however, how many people take the time to fill milk jugs or soda bottles with tap water and store it as part of their disaster-supply kits.

The issue of expiration dates is a long-running one that extends beyond water. Though government regulations require expiration dates on certain foods and medicines, critics say some prompt consumers to unnecessarily toss things out and re-stock. A study by the U.S. military in the 1980s found that 90% of the prescription and over-the-counter drugs it studied were effective well past their expiration dates.

To some degree, the fact that bottled water carries expiration dates can be blamed on New Jersey, the only state that officially requires it. That regulation dates back to 1987, though it's not completely clear what prompted it. The New Jersey Department of Health and Senior Services says only that: "The intent of the law was to protect the safety and quality of drinking water."

The industry says that, given the New Jersey law, it's easier -- and cheaper -- for water companies to stamp dates on every bottle, whatever the destination, than to do it selectively. "That's why you'll see it, so you don't have a hodgepodge of labels going to different states," says Stephen Kay of the International Bottled Water Association, an industry trade group. (A handful of other states, including New York, Michigan and Louisiana, require manufacturers to stamp packages with the bottling date, but don't insist on expiration dates.)

Some consumers don't take the expiration dates on bottled water all that seriously. John Rosenblatt, a 35-year-old television producer in New York, has stashed a five-gallon jug of water and a couple of cases of Poland Spring along with the canned food, gas masks and money he says he might need in an emergency. He plans to keep the water after its expiration date -- and drink it.

Others outside of the industry back the notion that the taste of a bottle of water can shift slightly over time. One explanation, according to some, is that the minerals that either naturally occur in some bottled water or are added during manufacturing may settle. The result can be water that tastes stale. "I don't think it would be a safety problem, but more of a quality issue," says Michael P. Doyle, director of the Center for Food Safety at the University of Georgia. "We've had some water that tasted like stale milk."

For that reason, some big grocery chains say they won't let old water sit on their shelves. Albertsons Inc., which operates 2,300 stores across the country, says it sends water that is past its stated expiration date back to the manufacturer.

The type of bottle used can also be a factor in the taste. The cheaper kind of translucent plastic used for milk jugs and some gallon containers of water can eventually leach a plastic tinge into the water. (Most bottled water, however, is packaged in a higher grade of plastic that is much more resistant to leaching.) See We Can Live With Much Less Plastic.

As for the expiration dates on bottled water, a renaming may be in order. The expiration date on the bottles of Dasani water, for instance, "isn't really an expiration date," says Ms. McDermott, of Coca-Cola. "It is more of an optimal taste date."

A Bottled-Water Lexicon

Labels sport all sorts of vague terms that can make it difficult to figure out what you're drinking. Below, a guide to some of the more popular varieties:

Mineral water: Unlike some waters, this contains a minimum amount of dissolved minerals and other elements. Water is derived from a protected underground source.

Spring water: Retrieved from a natural spring. With the exception of fluoride, no minerals are allowed to be added.

Artesian water: From a well that taps an aquifer, an underground layer of earth that contains water.

Purified water: Water has undergone a process to remove minerals, metals and other substances. The source is usually tap or spring water.

Drinking water: General term means the water is intended for people to drink -- but the term doesn't tell you anything about where it's from or how it's been processed.

Nine Unexpected Things in Drinking Water
By Dana Chivvis Sphere

(Dec. 8) -- Charles Duhigg of The New York Times today delivered the latest unsettling news about the nation's water supply: It's not as clean as you might think. An analysis of federal data from the last five years revealed that more than 20 percent of the nation's water-treatment systems have broken provisions of the Safe Drinking Water Act, the standards enforced by the Environmental Protection Agency. The result? As many as 19 million Americans are sickened each year.

Over the years, the EPA has identified many substances in water supplies far and wide. Here are nine unexpected things that they've spotted.

ARSENIC A naturally occurring element found in soil and minerals, arsenic is used as a pesticide and wood sealant. Ingesting high levels of arsenic, Madame Bovary can tell you, is deadly. At lower levels, over longer periods of time, it can darken skin and spur corns and warts. A carcinogen, arsenic can increase the risk of skin, liver, bladder and lung cancers.

The EPA has said that more than 3 million Americans have been exposed to water with illegal concentrations of arsenic since 2005.

URANIUM The element Iran insists on enriching despite howls from the U.S. and other Western nations, it is also used in helicopters, airplanes, armor, fertilizer and household items like certain microwaves. After it's mined and processed, some of it is released back into the environment in waste material, called mill tailings. Large amounts of uranium can lead to kidney disease and cancer, though naturally occurring uranium is much less radioactive.

The EPA says levels of uranium in drinking water are usually low and safe, according to the Agency for Toxic Substances and Disease Registry. However, the 3 million Americans exposed to illegal amounts of arsenic were also exposed to illegal amounts of radioactive substances.

RADIUM This radioactive metal has been used to treat cancer, for scientific research and in instrument calibration. Everyone is exposed to low levels of the substance, but higher levels are found near uranium mines, coal-burning industries and sometimes in drinking water that comes from wells. Radium can cause anemia and cataracts. At high levels, it is a carcinogen, causing increased bone, liver and breast cancer.

The EPA has reported that levels of radium were 2,000 times the legal limit in water flowing in some areas.

TETRACHLOROETHYLENE Used in dry cleaning and for metal degreasing, this chemical usually evaporates when it meets water, soil or air, but high exposure can cause headaches, dizziness, confusion, nausea and unconsciousness. Women who are exposed to high levels of tetrachloroethylene may have menstrual problems and even spontaneous abortions. It is also believed to be a carcinogen.

The New York Times found that the drinking water in Ramsey, N. J., located 35 miles outside of New York City, has had illegal concentrations of tetrachloroethylene since 2004.

LEAD Houses built before 1986 are more likely to have lead pipes than newer ones. Because hot water dissolves lead more easily, people who live with older plumbing should never drink hot water from the tap. Kids who drink lead-tainted water above the legal limits are at risk for physical and mental development problems. In adults, lead can lead to high blood pressure and kidney trouble.

The EPA's threshold for lead is 0.015 parts per million. If you are concerned about the levels of lead in your water, you can have it tested at a certified laboratory.

PROZAC, BIRTH CONTROL, MAKEUP, SHAMPOO Along with deceased goldfish and incriminating evidence, it turns out Americans like to flush their drugs and personal care products down the toilet, too. These substances leave the toilet (or bathtub and shower) and end up in our waterways. In fact, most of the waterways the EPA tested had pharmaceuticals and personal care products (PPCP's) in them.

While there is evidence that ecological harm can come from PPCP's in the water, scientists are not yet sure of the threat to humans.

You can find reports on the drinking water in your area here at the EPA Web site.