Lithium Levels in Umbilical Cord Blood from Two Cities in China: Indicating Unidentified Sources of Human Exposure

As lithium demand continues to grow, increasing environmental lithium concentrations pose potential health risks to sensitive populations, particularly pregnant women and fetuses. However, data on fetal lithium exposure and umbilical cord blood lithium concentrations in nonpolluted regions remain scarce. To address this gap, we monitored lithium concentrations in maternal and umbilical cord blood in Beijing and Changsha, and analyzed exposure sources using a one-compartment model. Significant regional differences were observed: in 2019 and 2021, the mean (±SD) of lithium concentrations in umbilical cord blood in Beijing were 13.05 ± 7.34 and 11.23 ± 2.56 μg/L, respectively, while in Changsha, a significantly lower level of 0.61 ± 0.64 μg/L was found. Model estimates indicated that umbilical cord blood lithium in Changsha primarily originated from cereal, vegetables, and drinking water. However, most of the lithium in Beijing's cord blood came from unidentified sources, likely anthropogenic. This study highlights significant regional differences in umbilical cord blood lithium exposure and underscores the existence of unidentified exposure sources in Beijing except natural resource. As lithium usage increases in the future, ongoing monitoring and evaluation of potential health risks to fetuses will be critical.