Questionable lead reporting for drinking water virtually vanished after Flint water crisis, study reveals
UMass Amherst economists employ new statistical tools to detect suspicious reporting
Public water systems in the U.S. were far less likely to report suspiciously rounded lead levels after the Flint, Michigan water crisis drew national outrage and federal scrutiny, according to new research led by the University of Massachusetts Amherst.
The study, published as the first article in the latest issue of American Economic Review: Insights, introduces new statistical methods to distinguish between natural rounding and potential “threshold manipulation” in reported figures.
“Existing methods can mistake rounding for manipulation,” explains Tihitina Andarge, assistant professor of resource economics at UMass Amherst. “Our approach allows us to separate the two.”
Andarge, David A. Keiser, professor of resource economics at UMass Amherst, Dalia Ghanem of the University of California, Davis, and Gabriel E. Lade of The Ohio State University analyzed how water systems reported lead concentrations from 2011 to 2020 under the Lead and Copper Rule, a key provision of the Safe Drinking Water Act. The rule requires systems to determine whether the 90th percentile of the lead concentrations in their water samples exceeds federal thresholds that can trigger additional monitoring, remediation and public notification.
The Environmental Protection Agency (EPA) relies on self-reported figures from about 50,000 water systems nationwide. Systems with reported lead levels above 0.005 milligrams per liter must continue frequent testing, while those above 0.015 must take costly corrective steps and notify the public. This creates an incentive for systems to report values just under the cutoffs.
The study found that before the Flint crisis prompted a state of emergency in 2016, about 3% of medium-sized systems and about 0.5% of small systems reported lead concentrations rounded exactly to the federal threshold—a pattern the researchers say is statistically unlikely to occur by chance. After Flint, those suspicious clusters all but vanished, and reported data aligned more closely with expected distributions.
Andarge notes that among small water systems, this pattern was concentrated in Alabama, while among medium-sized systems, it appeared throughout the country, though at a smaller scale.
The Flint crisis, which exposed thousands to dangerous lead levels, heightened public and regulatory attention to water safety nationwide. The EPA issued new guidance discouraging questionable testing practices, such as sampling lower-risk homes or manipulating collection procedures.
“We want to make sure that our drinking water systems are following through on the correct ways to measure for lead concentrations, so that people can take corrective actions if they need to,” Keiser says.
While the study does not allege deliberate fraud, it points to vulnerabilities in how the U.S. monitors drinking water quality. The authors warn that without continued oversight, some systems may again face incentives to downplay lead risks.
The EPA revised the Lead and Copper Rule, which covers more than 90% of the U.S. population, in 2021 and 2024. Lead exposure, even at low levels, has been linked to developmental delays in children and cardiovascular problems in adults.
Keiser adds that the new statistical methods could be applied to other areas where threshold manipulation is a concern, including air quality monitoring and academic testing.
The research was supported by the National Institutes of Health.
Journal
American Economic Review Insights
Method of Research
Data/statistical analysis
Protecting public health: Rice’s Stadler honored by The Water Research Foundation
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Lauren Stadler, associate professor of civil and environmental engineering at Rice University.
view moreCredit: Rice University.
The Water Research Foundation (WRF) recently presented Lauren Stadler, associate professor of civil and environmental engineering at Rice University, with the 2025 Paul L. Busch Award at the Water Environment Federation’s Technical Exhibition and Conference in Chicago. With this $100,000 research prize, Stadler plans to advance wastewater monitoring through the investigation of real-time biosensors that utilize synthetic biology.
In addition to her roles at Rice, Stadler also serves as co-lead of the Houston Wastewater Epidemiology System and as an associate editor for the journal Environmental Science: Water Research and Technology. She has received many awards throughout her career for her research and teaching achievements.
Most existing wastewater surveillance systems depend on collecting and transporting samples to centralized laboratories for analysis. This approach is slow, costly and limits real-time responsiveness. To address this, there is a need for technologies that enable decentralized, continuous detection of disease targets and health-relevant biomarkers directly within wastewater infrastructure. Stadler will focus on developing a new class of real-time biosensors that harness engineered microorganisms. She aims to develop new monitoring technologies that allow for near-instantaneous detection of pathogens, health biomarkers and chemicals without requiring sample processing or lab-based instrumentation. With this prize, her group will study the performance of biosensors in wastewater systems and model their strategic deployment for early detection of disease outbreaks.
“I’m honored to receive the Paul L. Busch Award,” Stadler said. “Our vision is to harness microbes as precise sensors and build a decentralized, real-time monitoring network for detecting pathogenic threats in wastewater. This work builds on my group’s efforts to make wastewater-based epidemiology a cornerstone of public health surveillance, while integrating cutting-edge advances from synthetic biology. I’m proud of my team’s accomplishments and excited about the path ahead as we develop novel biosensing platforms that can transform how we monitor wastewater to protect public health.”
The Paul L. Busch Award is made possible by the Endowment for Innovation in Applied Water Quality Research and has provided $2.4 million in funding to up-and-coming researchers making major breakthroughs in the water quality industry.
