Despite the prevalence of drinking water contamination in the United States, its health effects are not well understood. Unlike the extensive research on health impacts of air pollution, studies on water contamination are limited, mainly due to a lack of high-frequency water contamination data. To address this gap, I construct a novel dataset of monthly nitrate contamination levels in California’s community water systems linked with individual birth records. Nitrate contamination is a persistent issue in water systems in the United States, posing a potential threat to infant health. This study estimates the effect of prenatal exposure to nitrate contamination below current regulatory limits on birth outcomes. Using a panel fixed-effects approach with water system and time fixed effects, I compare birth outcomes across infants from the same water system who were exposed to differing levels of nitrate contamination during each trimester of gestation. I find that second-trimester exposure to nitrate concentrations below regulatory limits increases the likelihood of preterm birth and low birth weight by 1.2 and 1 percentage point, respectively. Relative to sample means, these estimates translate to a 15 % increase in the probability of preterm birth and a 17 % increase in the probability of low birth weight birth. Results further suggest that lowering the current regulatory limit below 5 mg/L (half the current limit) could prevent nitrate-related adverse birth outcomes.
While a large economic literature shows that privatization improves efficiency and profitability, its effects on quality are less well understood. This gap is particularly important in essential public services, where recent policy reforms have strengthened incentives for private acquisition and positioned it as a potential remedy for fiscal stress in public provision. We estimate the impact of privatization on quality in the context of U.S. drinking water systems using a propensity-weighted difference-in-differences design. We show that privatization leads to substantial improvements in regulatory compliance, reducing total Safe Drinking Water Act violations by 1.3 (88%), driven largely by reductions monitoring and reporting violations. By contrast, we find only limited evidence of declines in regulated contaminant concentrations. These improvements are not explained by increased infrastructure construction and instead appear to reflect cost-reducing reorganization, including greater worker specialization and increased access to specialized human capital. Our findings inform a central policy question about the role of private provision in essential public services, suggesting that privatization can improve regulatory compliance, though the incentives surrounding private acquisition, together with the broader regulatory environment, may limit improvements beyond regulatory minimums.
Policymakers are increasingly turning to drinking water system consolidation to address persistent water quality and compliance challenges in under-resourced communities. Consolidation is a common strategy for capturing economies of scale across industries, yet evidence on how it affects quality is limited. I estimate the effects of drinking water system consolidation in California using a staggered difference-in-differences design, focusing on outcomes consumers directly experience: regulatory violations, contaminant concentrations, and monthly bills. Consolidation reduces total Safe Drinking Water Act violations by 64%, with declines in health-based and monitoring and reporting violations and in indices of contaminant concentrations. These pooled effects mask substantial heterogeneity: among systems designated as failing before consolidation, consolidation leads to approximately 1.24 (48%) fewer total violations per year, with little change in monthly bills. Consolidations involving systems without prior compliance struggles show little change in violations but suggestive evidence of lower bills. Receiving systems experience no statistically significant increase in operating expenses. Overall, the results suggest that consolidation can improve drinking water quality for communities served by struggling systems without imposing substantial costs on the systems that receive them.
Impact of Wildfire on Water Quality, Treatment Costs, and Consumer Rates (with Grant Webster)
Predicting Failing Water Systems (with Adrienne Ohler)
Externalities of Agriculture: Fertilizer Use and Its Impact on Drinking Water Quality