As public skepticism about water quality rises in the United States, more people opt for bottled or home-treated water instead of drinking straight from the tap.
But is this truly a safer choice?
A recent study examining water quality in California's San Francisco Bay Area suggests it might not be.
The research, published in PLOS Water, found that tap water, home-treated water, and bottled water in the region all contained trihalomethanes (THMs), cancer-causing compounds formed during water disinfection. This issue likely extends beyond the Bay Area to much of the country.
"We've looked at aesthetic contaminants versus health contaminants in our research, and a lot of those things that people are perceiving as contaminants in their water aren't connected to health impacts at all," Samantha Bear, senior research scientist at SimpleLab and lead author of the study, told Newsweek.
Despite these findings, the consumption of bottled water in the U.S. has soared, from 27.8 gallons per person annually in 2010 to 45.2 gallons in 2020, according to the study. This surge is driven mainly by the public perception that tap water is unclean or unsafe, exacerbated by incidents like the Flint Water Crisis in April 2014.
Home water treatment systems are also gaining popularity, with the market reaching $2.09 billion. However, many consumers are unaware of the specific contaminants they aim to avoid, often prioritizing taste or appearance while incurring significant economic and environmental costs.
The study found that while tap water had the highest potential toxicity among the three water sources tested, bottled and home-treated water still posed health risks.
THMs, the compounds identified in all water types, are associated with long-term health issues, including bladder and colon cancer, as well as reproductive problems and birth defects, according to Delaware Health and Social Services.
Though the THM levels detected did not exceed regulatory limits, they were higher than recommended health benchmarks.
"So when we say this contaminant exceeded the limits, we mean it exceeded the health benchmarks, meaning the concentration at which if you were drinking that over the course of your lifetime we would expect there to be a potential health risk," Jessica Goddard, chief science officer at SimpleLab, told Newsweek.
"It's not like someone's going to drink one of these samples and get bladder cancer. We want to make that really clear because, for the most part, these contaminants are within regulatory levels."
The study used the Bay Area as a representative location, where residents have access to tap, home-treated and bottled water. The authors believe that while toxicity levels might vary in other regions, the overall findings would likely be similar.
So, what can be done to address these concerns?
"One takeaway is that you can treat your water at home instead of buying bottled water. If you tailor the treatment that you're providing at your home to what is actually in your water, then we expect that the contaminant load in your household treated tap water would be even lower," Bear said.
Goddard added, "Regulators could be more stringent on the trihalomethane concentrations allowed in drinking water instead of shifting the burden on individuals, which will obviously have economic implications based on who can afford treatment."
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References
Bear, S. E., Waxenberg, T., Schroeder, C. R., Goddard, J. J. (2024). Bottled water, tap water and household-treated tap water–insight into potential health risks and aesthetic concerns in drinking water. PLOS Water. https://doi.org/10.1371/journal.pwat.0000272
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