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Philadelphia Water Department, 1500 E. Hunting Park Avenue, Philadelphia, Pennsylvania 19124, United States.
Environ Sci Technol. 2021 Sep 7;55(17):11491-11500. doi: 10.1021/acs.est.1c00421. Epub 2021 Aug 9.
The United States Environmental Protection Agency recently released their most sweeping overhaul to the Lead and Copper Rule in three decades. One of the most significant changes is requiring a fifth-liter (L5) sample at homes with lead service lines (LSLs) rather than the original first-liter (L1) sample for a demonstration of compliance with water lead level (WLL) limits. We analyzed sequential sampling data from three large water systems and compliance data from Michigan utilities-which base compliance on the 90th percentile of the greater of L1 and L5 samples-to evaluate whether L5 WLLs better represent water in contact with LSLs and to explore regulatory impacts of including L5 samples in compliance monitoring. The sequential sampling data demonstrated that it is impossible to use a single sample volume within a sequential profile to universally capture the volume of water in an LSL. While L5 is not always a reliable indicator of water in contact with an LSL, Michigan compliance data showed that the L5 sample is more likely to be from an LSL and can identify utilities that benefit from an improved corrosion control treatment. Michigan compliance data indicate that it is likely that L5 sampling will result in more systems having a higher 90th percentile WLL and that a high proportion of the systems likely to exceed regulatory action levels based on L5 samples can be identified through a retrospective analysis of historic L1 data. The impact of the switch to L5 sampling on the effectiveness of corrosion control treatment over time has yet to be determined.
美国环境保护署最近对三十年来的《铅和铜规则》进行了最全面的修订。其中一个最重要的变化是，对于有铅服务管（LSL）的家庭，要求采集第五升（L5）样本，而不是原来的第一升（L1）样本，以证明其符合水中铅含量（WLL）限制。我们分析了来自三个大型供水系统的序贯采样数据和密歇根州公用事业公司的合规数据（这些公司根据 L1 和 L5 样本中较大的第 90 百分位数来确定合规性），以评估 L5 WLL 是否更好地代表与 LSL 接触的水，并探讨在合规监测中纳入 L5 样本对监管的影响。序贯采样数据表明，不可能在序贯样本中使用单一的样本量来普遍捕捉 LSL 中的水量。虽然 L5 并不总是与 LSL 接触的水的可靠指标，但密歇根州的合规数据表明，L5 样本更有可能来自 LSL，并可以识别出受益于改进的腐蚀控制处理的公用事业公司。密歇根州的合规数据表明，L5 采样可能导致更多系统的第 90 百分位数 WLL 更高，并且可以通过对历史 L1 数据的回顾性分析来识别出很大比例的系统可能会超过基于 L5 样本的监管行动水平。随着时间的推移，切换到 L5 采样对腐蚀控制处理效果的影响尚未确定。
