Estimating the impact of the proposed Lead and Copper Rule Improvements

Lead in drinking water can lead to serious health effects, including neurodevelopmental issues and heart disease. In December 2023, the U.S. Environmental Protection Agency (EPA) proposed the Lead and Copper Rule Improvements (LCRI), which lower the Lead and Copper Rule's (LCR's) lead action level (AL) from 15 parts per billion (ppb) to 10 ppb and require both first- and fifth-liter sampling and 90th percentile compliance calculations based on the highest lead levels at sites with lead service lines. A methodology for estimating the likelihood a system will have an AL exceedance (ALE) under the LCRI was developed using Michigan LCR compliance data and applied to national LCR compliance data. Findings were compared to EPA's estimates, indicating EPA may have underestimated the percent of smaller systems (serving $\le$ 3300) with ALEs and overestimated the percent of larger systems (serving > 10,000), thus underestimating costs and overestimating the benefits of this rulemaking.