A new study has found that there are dozens of unregulated harmful chemicals in a number of popular brands of bottled water.
The study, published by the journal Science Direct, reviewed 64 regulated and unregulated disinfection by-products (DBPs) in 10 popular brands of bottled water, and found that all bottled water examined contained DBPs.
However, these findings are not entirely negative for bottled drinking water. Susan Richardson, a professor of chemistry at the University of South Carolina, and one of the authors of the study, told Newsweek: "The bottled waters we tested were less contaminated with DBPs than tap water."
"Overall, I think this is a good finding for bottled water. Before this study, there was almost no information on the vast majority of toxic priority, unregulated DBPs. Now we have it," she said.
Why It Matters
Disinfecting drinking water is a hugely important part of the water treatment process, as it ensures those who drink the water are not exposed to cholera, typhoid and other microbial diseases.
However, this process can result in DBPs contaminating the water. The concern is that these chemicals can have harmful impacts on human health.
"Many human epidemiologic studies show a risk of bladder cancer; some show a risk of colorectal cancer, and some show a risk of miscarriage and birth defects," Richardson said. These risks have been found in a number of studies.
What To Know
The brands examined in the study were unnamed, although the authors noted that "grocery" and "name" brands had higher numbers of DBPs compared with "designer" brands.
Additionally, brands sourced from spring water generally showed lower overall DBP levels than those labeled as purified, the authors added.
Two "grocery" brands had used purified tap water for its bottled water and they had "significantly higher calculated cytotoxicity than other bottled waters sampled," the authors noted, with 43 times and 83 times the average levels of other bottled waters.
There are a number of ways that bottled water can become contaminated with DBPs. Richardson said that many brands of bottled water use tap water that has been "further purified," but that not all the DBPs get removed in that process.
She said that some bottled waters are also treated with ozone, an effective disinfectant, and that ozone can form DBPs. She also said that some spring water can be infiltrated with surface waters that are contaminated with DBPs as well.
While many DBPs were found in the bottled water, the types that were most concerning included brominated DBPs, particularly dibromoacetonitrile, which Richardson said "is a carcinogen and is not regulated." But, she added that levels of this chemical were quite low, and were similar to what can be found in tap water.
Alongside dibromoacetonitrile, a number of other unregulated DBPs were found in bottled water for the first time, the study authors said.
These included chloroacetonitrile, dichloroacetamide, trichloronitromethane, dichloroacetaldehyde, 1,1-dibromopropanone, and 1,1,1-trichloropropanone. Total organic halogen (TOX) was also measured in bottled waters for the first time, they added.
The Food and Drug Administration (FDA) does regulate some DBPs in bottled water, such as bromate, chlorite, and haloacetic acids, and also the total level of DBP trihalomethanes, but Richardson said that the unregulated DBPs in her study refer to those that the U.S. Environmental Protection Agency (EPA) "does not regulate in drinking water and would also not be regulated in bottled water."
In comparison to tap water though, bottled waters have fewer DBPs. The authors noted that there were on average 3 types detected in bottled water compared with 37 in tap water.
What People Are Saying
Sherri Mason, director of Project NePTWNE, a project seeking to improve water quality, at Gannon University, told Newsweek: "It is interesting that the DBPs are lower in bottled water compared to tap water—though that is exactly what the companies promote so they should be. I think it is most surprising given the number of studies that have found other, unexpected, toxicants within bottled water that are not normally tested for, such as benzene and micro- or nano-plastics."
Mason added: "In my opinion tap water is still safer than bottled water. This is one small study that used only local tap water for comparison and was focused on only one suite of potential chemical toxicants. Given the body of research outside of this study showing elevated concentrations of other chemicals of concern, including micro- and nano-plastics, at levels hundreds to thousands of times higher within bottled water compared to tap water, and considering that tap water is tested dozens of times a day, while bottled water is largely unregulated, I stand with the science and the regulatory framework that tap is safer."
Natalie Exum, a professor in the Department of Environmental Health and Engineering at Johns Hopkins Bloomberg School of Public Health, told Newsweek: "I was not surprised by the findings from this study that bottled water contained fewer DBPs and at lower levels than were present in tap water. This is because we know chemical disinfectants are required to be in public tap water to reduce microbial contamination however they can also result in DPBs. In bottled water, these DPBs may be removed through the "purification" processes or not used at all if it is coming from a spring or natural source so I would expect there to be lower DPBs in bottled water."
Exum said: "Unregulated DBPs are of greatest concern because of their toxicological profile, however, study of their health effects has not produced evidence that has required them to be regulated yet. This means that we may be consuming them without proper understanding of their harm to our health. Since the levels were much higher in regulated public tap water, my main take away from this study is that DBPs are actually less of a concern in bottled water."
She added: "My main takeaway from this study is that we need to be expanding regulation for DBPs of greatest concern to health in public drinking water because this will have the greatest impact on the health of the population."
Vasilis Vasiliou, chair and professor of Environmental Health Sciences at Yale School of Public Health, told Newsweek: "The discovery of 50 plus priority unregulated DBPs (like dibromoacetonitrile, chloroacetonitrile, dichloroacetamide, and trichloronitromethane) in bottled water is striking because these compounds are not routinely monitored and little data existed on their presence in bottled products until now. Finding haloacetic acids (HAAs) and chloroform even in waters labeled as UV-treated only suggests cross-contamination or incomplete processing, which challenges assumptions about how 'pure' certain treatments are."
Vasiliou said: "DBPs form when chlorine or similar disinfectants react with organic matter in water. Some, including HAAs, are linked to higher cancer risk and possible reproductive or developmental effects with long-term exposure. Finding them in bottled water is concerning because consumers often choose it to avoid contaminants."
He added: "Neither option is universally safer. Tap water is more strictly and transparently regulated, while bottled water may have lower levels of some by-products but is often sourced from the same systems and tested less frequently. For most people, properly treated tap water—especially with basic home filtration—is a safe and practical choice."
What Happens Next
Despite the findings, and other research on the possible risks of DBPs to human health, Richardson said that she "would never suggest that people switch from their tap water to bottled water unless they know they have a major contamination issue with their tap water."
"I think of all the plastic that gets into the environment from bottles," she said. "And, the cost is so much higher to buy bottled water."