Water Quality of U.S. Drinking Water Kiosks: Lead Release from "Lead-free" Plumbing after Reverse Osmosis Treatment

Many Americans distrust tap water, leading them to purchase more expensive drinking water sold from water vending machines (e.g., kiosks) that are poorly regulated and sparingly monitored for quality. Here, we analyzed the water quality of 20 kiosks from 4 different manufacturers across 6 states in the first comprehensive comparison of the chemical and microbial characteristics of kiosk water to paired tap samples. Of the 16 kiosks listing specific water treatment processes (others indicated "filtered" or "purified"), only 1 dispensed water with ionic composition (e.g., Na⁺, Ca²⁺, Mg²⁺) inconsistent with the stated treatment. Most kiosks tested used reverse osmosis (RO), which removed fluoride and residual disinfectant, although we found no evidence of microbial contamination. RO also provided the benefit of removing per- and polyfluoroalkyl substances. However, we frequently detected higher lead levels in kiosk water than in nearby tap water. Lead was detected (>0.05 μg/L, our method detection limit) in 15 kiosks; 5 were >1 μg/L (American Academy of Pediatrics recommendation), 2 were >5 μg/L (FDA allowable level for bottled water), and 1 was >10 μg/L (US EPA Action Level). Lead co-occurred with zinc and copper, consistent with corrosion of lead-containing plumbing materials. XRF analysis of plumbing in 2 kiosks from different manufacturers with nationwide distribution confirmed this suspicion although all components in question met the definition of lead free under the Safe Drinking Water Act. Lead release was most evident with the use of RO treatment, which can produce corrosive water low in alkalinity and pH. Going forward, the removal of lead-containing plumbing components downstream of RO treatment and regulation with routine testing of kiosk water quality is imperative to address this unchecked public health risk.