Newswise — After high-profile water crises like the one in Flint, Michigan, some Americans distrust the safety of tap water, choosing to purchase drinking water from freestanding water vending machines or kiosks. Yet this more expensive water may contain different pollutants than local tap water, according to a study in ACS’ Environmental Science & Technology. Researchers report that water sampled from 20 kiosks in six states sometimes contained lead at levels above public health recommendations.

“Currently, water kiosks are not regulated the same as tap water; their water is not tested for lead or other metals,” says Samantha Zuhlke, a corresponding author of this study. “Updating water kiosk regulations can improve their quality and help consumers make informed decisions about the water they are drinking.”

Water kiosks are privately owned vending machines that are often marketed as being safer than tap water, commanding prices of $0.25-$0.35 per gallon (compared to less than 2 cents per gallon for tap water in most U.S. cities). Kiosk operators generally treat local tap water with purification techniques such as filtration, ultraviolet light or reverse osmosis (RO) to remove potentially harmful contaminants such as lead, microbes, residual disinfectants, and per- and polyfluoroalkyl substances (PFAS). But water vending machines in the U.S. are poorly regulated. So, a team of researchers led by Zuhlke and David Cwiertny conducted a comprehensive comparison of the chemical and microbial characteristics of kiosk water and tap water from municipalities close to the monitored kiosks.

The team collected water samples from 20 kiosks operated by four different manufacturers across Iowa and in the surrounding states of Illinois, Kansas, Missouri, Arkansas and Oklahoma. Most of the kiosks advertised treatment of their water by RO, a process that uses pressure to force water through a semipermeable membrane, purifying the water and leaving most contaminants caught behind the membrane. For comparison, the researchers collected tap water samples from community sources within a mile of each kiosk.

They analyzed all samples and found no evidence of microbial contamination in any sample. They also found that RO treatment in kiosks effectively removed most PFAS from the sourced tap water. However, this benefit was offset by concerning levels of lead in some RO-purified kiosk water samples — nearly twice the concentration recommended by the U.S. Environmental Protection Agency.

The researchers traced the lead to the corrosion of brass plumbing in the kiosks following RO treatment. Although the plumbing components are marketed as “lead-free,” small amounts of the metal can leach under the low-pH and low-alkalinity conditions of RO-treated water, they say. Replacing the internal metal pieces with other materials could eliminate lead in dispensed water.

“This work adds to growing evidence that allowable levels of lead in ‘lead-free’ plumbing can still be problematic sources of lead in drinking water when such plumbing is exposed to certain types of water, like that generated after RO treatment,” Cwiertny says.

The authors acknowledge funding from the University of Iowa’s Center for Social Science Innovation and the Office of Undergraduate Research. This work was conducted through the University of Iowa Center for Health Effects of Environmental Contamination, which receives support through the Iowa Department of Natural Resources.

The paper’s abstract will be available on Feb. 11 at 8 a.m. Eastern time here:   

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Newswise — Environmental pollutant analysis typically requires complex sample pretreatment steps such as filtration, separation, and preconcentration. When solid materials such as sand, soil, or food residues are present in water samples, analytical accuracy often decreases, and filtration can unintentionally remove trace-level target pollutants along with the solids.

To address this challenge, a joint research team led by Dr. Ju Hyeon Kim at the Korea Research Institute of Chemical Technology (KRICT), in collaboration with Professor Jae Bem You’s group at Chungnam National University, has developed a microfluidic-based analytical device that enables direct extraction and analysis of pollutants from solid-containing samples without any pretreatment.

Water, food, and environmental samples encountered in daily life may contain trace amounts of hazardous contaminants that are invisible to the naked eye. Accurate detection requires selective extraction and concentration of target analytes, a process traditionally achieved using liquid–liquid extraction (LLE). However, conventional LLE requires large volumes of solvents and is difficult to automate. Although liquid–liquid microextraction (LLME) has been introduced to overcome these limitations, its practical application has remained limited because samples containing solid particles still require a filtration step prior to extraction.

Existing analytical approaches typically follow a multistep workflow—solid removal, extraction, and analysis—which increases time and cost while reducing analytical reliability. These limitations pose significant challenges in fields closely related to public health, including environmental monitoring, drinking water safety, and pharmaceutical residue analysis.

The research team overcame these issues by designing a trap-based microfluidic device that confines a small volume of extractant droplet inside a microchamber while allowing the sample solution to flow continuously through an adjacent microchannel. This configuration enables rapid and selective mass transfer of target analytes into the extractant, while solid particles pass through the channel without interference. After extraction, the extractant droplet can be retrieved for downstream analysis.

Using this device, the researchers successfully detected perfluorooctanoic acid (PFOA), a representative per- and polyfluoroalkyl substance (PFAS) increasingly regulated due to environmental and health concerns, as well as carbamazepine (CBZ), an anticonvulsant pharmaceutical compound. Notably, CBZ was extracted directly from sand-containing slurry samples without filtration. PFOA signals were detected within five minutes, and CBZ extracted from slurry samples was clearly identified using high-performance liquid chromatography (HPLC).

The results demonstrate that the proposed microfluidic platform significantly reduces analytical steps while maintaining high reliability, highlighting its potential as a compact and automatable solution for environmental pollution monitoring, food safety inspection, and pharmaceutical and bioanalytical applications.

Dr. Kim noted that “integrating multiple pretreatment steps into a single process offers substantial advantages for on-site analysis and automated systems,” while KRICT President Young-Kuk Lee emphasized that “this technology can enhance the reliability of environmental and food safety analyses that directly impact public health.”

The study was published as a cover article in ACS Sensors (Impact Factor: 9.1; top 3.2% in JCR Analytical Chemistry) in December 2025. Dr. Ju Hyeon Kim (KRICT) and Professor Jae Bem You (Chungnam National University) served as corresponding authors, with Sung Wook Choi as the first author.

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KRICT is a non-profit research institute funded by the Korean government. Since its foundation in 1976, KRICT has played a leading role in advancing national chemical technologies in the fields of chemistry, material science, environmental science, and chemical engineering. Now, KRICT is moving forward to become a globally leading research institute tackling the most challenging issues in the field of Chemistry and Engineering and will continue to fulfill its role in developing chemical technologies that benefit the entire world and contribute to maintaining a healthy planet. More detailed information on KRICT can be found at https://www.krict.re.kr/eng/

The research was supported by the KRICT Core Research Program, the National Research Foundation of Korea, and the Korea–Switzerland Innovation Program.