Widespread nickel contamination in drinking water supplies of elementary schools in Taichung, Taiwan

Owing to the limited information regarding potential sources of nickel (Ni) in drinking water, incidences of Ni contamination have not been well elucidated in the literature. However, in recent decades, Ni-containing plumbing materials such as stainless steel pipes, brass fittings, and chrome faucets have gained popularity in drinking water distribution systems. As a result of increased use of such materials, Ni levels in drinking water are expected to rise over time, posing long-term exposure risks to consumers. For the first time, this study employed an intensive sequential sampling, from October 2019 to July 2020, to assess Ni levels in drinking water samples collected from dispensers of elementary schools in Taichung, Taiwan. Of the total 580 sequential samples collected from 58 elementary schools, 45 samples from 17 schools exceeded the Taiwan Environmental Protection Administration (EPA) standard value of 20 μg/L for Ni. Total Ni concentration in 1 L sample, an average of the total Ni concentrations in 10 sequential samples, exceeded in 4 schools. This finding suggests minor Ni contamination in drinking water supplies across the city. The highest Ni concentration was measured in the 1st sequential sample reaching 154 μg/L. Weekend and summer samples exhibited a higher tendency to exceed the standard. Older schools with age above 50 years and schools with a higher student population (≥ 500) were more likely to have Ni contamination. This study showed that drinking water is a potential source of Ni. However, the identification of Ni source, whether within the dispenser or in the distribution system, warrants further research.