“How ‘pure’ is ‘purified,’ when the chemistry keeps a few receipts?” A laboratory examination of bottled water revealed that all samples contained disinfection by-products (DBPs), which are chemicals that can be created when water is treated to kill microbes. The study widened the focus from the few DBPs that are normally analyzed to include both regulated and priority unregulated compounds. The study also arrived at an unpleasant truth for anyone purchasing bottled water to avoid contaminants: some of what finds its way into the bottle is a result of treatment and not neglect.
In the study, 64 regulated and priority unregulated disinfection by-products were analyzed in 10 common bottled waters. Total DBPs in bottled waters ranged from 0.01 to 22.4 μg/L, with an average of 2.6 μg/L. For comparison, the total DBPs in a single sample of chloraminated tap water included in the analysis were 47.3 μg/L. On average, bottled waters contained around three detectable DBP species, while the tap water sample contained 37. This highlights why DBPs are, for many people, a tap water issue above all else.
One aspect on which the findings were surprisingly reassuring, according to Susan Richardson, a chemistry professor and author of the study, is the following: “The bottled waters we tested were less contaminated with DBPs than tap water,” she said in an interview with Newsweek. This is important because while DBPs are necessary for the prevention of microbial diseases, they have also been associated in epidemiological studies with health risks such as bladder cancer and pregnancy complications.
The more complex aspect is what seemed to be beyond the regulated list. There were some samples that had brominated DBPs, such as dibromoacetonitrile, which Richardson calls “a carcinogen and is not regulated.” The other DBPs that were detected for the first time in bottled water are priority and unregulated, and these include chloroacetonitrile, dichloroacetamide, trichloronitromethane, dichloroacetaldehyde, and some halogenated propanones. Total organic halogen, which is a more general metric that can suggest halogenated organic chemistry that is not detected by focused screening, was analyzed in bottled waters for the first time.
Why would any of this appear in a sealed bottle? Bottled water comes from sources that may already be using disinfection, and even further “purification” can result in DBPs remaining in the water. Some brands also use ozone, a potent disinfectant; a drawback is the possible creation of bromate during ozonation in bromide-bearing waters. Spring water may also be affected by surface water intrusion, which can contain residues from treatment processes.
The regulation is also not as broad as the marketing. The FDA regulation includes some DBPs in bottled water, and the FDA requires that the bottled water be tested at least once a year for these DBPs. The DBPs that are not regulated in the study mentioned above are the ones that are not tested annually.
Instead, it gives consumers a less sensational but more informative message: bottled water may contain fewer disinfection by-products than tap water, but still more chemicals than most people think. And then there are the questions raised by the bottle itself. Recently, a review of over 140 studies concluded that people may consume 39,000 to 52,000 microplastic particles per year, with bottled water drinkers consuming about 90,000 more than tap water drinkers. As with the chemicals, “clean” is a matter of what’s being measured. As Vasilis Vasiliou, chair of Environmental Health Sciences at Yale School of Public Health, told Newsweek: “Neither option is universally safer.”
