Many presumably do so out of a belief that bottled water is safer or more healthful than tap water.  Yet bottled water is much less stringently regulated than tap water -- and the Natural Resources Defense Council wants the Food and Drug Administration to tighten its regulations.

The NRDC recently released a study that found a third of 103 nationally-sold brands failed to meet industry or state purity standards.  It said 22 percent of the sample exceeded California's limits for aresnic and cancer-causing substances.

The NRDC wants the FDA to set strict limits for a wide variety of contaminants, including chlorine, arsenic, bacteria and organic and inorganic compounds. It also wants the FDA to regulate all water -- not just that sold in interstate commerce.

At present, bottled water sold within a single state is not regulated by the FDA and many states have little or no oversight of bottled water.   In contrast, state and county health departments routinely monitor the quality of municipal tap water.