After recent water crises such as the one in Flint, Michigan, some Americans have turned to freestanding water vending machines or kiosks as an alternative to tap water. These kiosks are often promoted as providing safer drinking water, but a new study published in ACS' Environmental Science & Technology suggests that this may not always be the case.
Researchers led by Zuhlke and David Cwiertny collected samples from 20 water kiosks across Iowa and nearby states including Illinois, Kansas, Missouri, Arkansas, and Oklahoma. The kiosks were operated by four different manufacturers and most used reverse osmosis (RO) treatment to purify local tap water before dispensing it for sale at prices between $0.25 and $0.35 per gallon—significantly higher than the cost of municipal tap water.
The study compared kiosk-dispensed water with tap water from community sources located within a mile of each kiosk. Tests showed no evidence of microbial contamination in any sample. Additionally, RO treatment was found to effectively remove most per- and polyfluoroalkyl substances (PFAS) from the source tap water.
However, researchers found that some samples of RO-treated kiosk water contained lead concentrations nearly twice as high as those recommended by the U.S. Environmental Protection Agency. The source of this lead was traced to corrosion in brass plumbing components inside the kiosks after RO treatment. Although these parts are labeled "lead-free," small amounts of lead can still leach into low-pH and low-alkalinity RO-treated water.
Cwiertny stated: "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."
The study suggests that replacing internal metal components with alternative materials could prevent lead contamination in kiosk-dispensed drinking water.
