High-precision Pb isotopes of drinking water lead pipes: Implications for human exposure to industrial Pb in the United States.

Millions of lead (Pb) pipes are still used in the drinking water distribution systems in many regions in the world. Human exposure to Pb from contaminated drinking water continues to be of concern in the United States (U.S.), as illustrated by the widely publicized "Flint Water Crisis" in 2015. The Pb isotopic composition of Pb-pipes potentially can be useful to identify human exposure to Pb from lead service lines (LSLs). In addition, as the LSLs were likely manufactured from similar industrial Pb sources as other Pb objects and materials in the USA, the Pb-pipes isotope data can provide information about the overall isotopic composition of the U.S. industrial Pb. In this work we present high-precision Pb isotope data from Pb-pipes excavated from different U.S. municipalities. The Pb-pipes show an extremely wide range of Pb isotopic compositions, with Pb/Pb ranging from 17.004 to 22.010, Pb/Pb from 15.460 to 15.921, and Pb/Pb from 36.687 to 41.120. The wide isotope range is observed even in a single town, suggesting that no regional Pb isotope patterns can be expected within the continental USA. However, the high-precision MC-ICP-MS Pb data form a clear linear trend that, depending on the context, can be used to identify human Pb exposure. Furthermore, as the linear trend is a result of utilization of Pb ores from different domestic and international sources and secondary recycling of metallic Pb, it is likely representative of the overall isotopic composition of the U.S. industrial Pb pool. Therefore, the identified trend is the most accurate isotope representation of the U.S. anthropogenic Pb at present and can be used as first-order evaluation to determine if a person with elevated blood Pb levels was exposed to U.S. industrial Pb sources.