Drinking water is essential for life and, in its most desirable form, is free of bacteria and chemical contaminants. Often, we assume that bottled water is cleaner than tap water, and in some parts of the world, that is certainly the case. Bottled water is popular in the U.S., outselling milk for the first time in 2006 (1). The largest consumer of bottled water (per capita) is Italy, hardly a developing nation (2). In the U.S., bottled water and drinking water contaminant regulations have been harmonized, so that both types of water should be of the same quality. However, in places with inadequate regulations or regulations that are not well enforced, bottled water can be more contaminated than expected.

Table I: U.S. primary and secondary drinking water contaminants

Water testing is critical to ensuring quality. Even though standards have been set and implemented to ensure the initial quality for a water, the bottling process can have unexpected consequences. For example, a famous bottled water was recalled after benzene was unexpectedly detected (3). A recent report found that 10% of bottled water in Shanghai, China, does not meet sanitary standards (4). Earlier this year, bottled water from Armenia was recalled because of contamination with more than 50 times the Food and Drug Administration–regulated amount of arsenic (5). Water is analyzed for three broad classes of contaminants: microbiological, organic, and inorganic. Inorganic contaminants include metals such as lead (Pb) and cadmium (Cd), that are clearly toxic. Some elements, such as selenium (Se), might be beneficial at low levels but toxic at higher concentrations. U.S.-regulated primary and secondary drinking water inorganic contaminant levels are shown in Table I.

Metals Analysis Helps Ensure Safety

Bottled water from around the world has been collected and analyzed to compare the inorganic contaminants to those allowed in the U.S. Several analytical techniques are suitable for the measurements, and in this case, inductively coupled plasma-mass spectrometry (ICP-MS) was chosen for speed and detection level, using Environmental Protection Agency (EPA) method 200.8 (6). Detection limits 10 times below the concentration at which decision-making is required generally are recommended. Consensus methods and U.S. EPA methods generally require a number of quality control tests interspersed with samples for analysis to ensure high-quality data results for these important measurements.

Table II: Drinking water contaminants measured in a variety of bottled waters (μg/L) using the PerkinElmer Sciex ELAN DRC II ICP-MS

Table II shows a variety of bottled water results. The results are below the regulatory limit in all cases. For many elements, the concentration is below the detection limit as measured using the EPA definition. For several bottled water samples, it is interesting to note the presence of uranium. Although it is below the regulatory limit, it is clearly present and can be detected at very low levels by ICP-MS.