Occurrence, distribution, and prioritization of unregulated emerging contaminants including battery-related chemicals in drinking water systems across South Korea.

This study investigated the presence of 95 emerging contaminants comprising pharmaceuticals, stimulants, artificial sweeteners, nicotine metabolites, corrosion inhibitors, battery-related pollutants, and pesticides across 70 drinking water treatment plants. Battery-related contaminants (lithium, nickel, and cobalt), with total concentrations raging from 424 to 38,500 ng/L (median 2560 ng/L) in the raw water and from 596 to 34,300 ng/L (median 2510 ng/L) in the treated water, showed the highest detection frequencies (≥99 %). The median levels of nickel (1440 ng/L in raw water and 1620 ng/L in treated water) were higher than those of lithium (591 ng/L in raw water and 445 ng/L in treated water) and cobalt (233 ng/L in raw water and 95.3 ng/L in treated water). Organic contaminants (raw water: 33.6-6540 ng/L, median 827 ng/L; treated water: not detected-1900 ng/L, median 121 ng/L) mostly had lower total levels than battery-related chemicals. Telmisartan (median 36.6 ng/L in raw water and median 7.47 ng/L in treated water) and valsartan acid (median 26.3 ng/L in raw water and median 6.61 ng/L in treated water) were the predominant pharmaceuticals. For corrosion inhibitors, benzothiazole (29.0 ng/L in raw water and 7.21 ng/L in treated water) displayed the highest median concentrations. Bentazone (median 119 ng/L) was the most predominant pesticide in raw water. The distribution patterns of contaminants in raw water were related to various pollution sources in industries, agricultural zones, and daily life. Additionally, rainfall increased the inflow of lithium, nickel, cobalt, and benzothiazole into public waterways. According to the human health risk assessment using the maximum levels of contaminants, lithium, nickel, cobalt, and valsartan acid were the priority contaminants in treated water, indicating potential risks or need for further evaluation. The priority contaminants with high or moderate risks to aquatic ecosystems in raw water were three battery-related chemicals, six pharmaceuticals, and five pesticides.