Polluted waters and municipal finance
Abstract
We show that pollution increases the offering yields of municipal bonds, indicating increased risk. We establish this using a difference-in-differences design, comparing the bonds from U.S. counties revealed to contain per- and poly-fluoroalkyl substances (PFAS) in their drinking-water supplies with the bonds from neighboring, unpolluted, same-state counties. The increase was greater for riskier bonds characterized by repayment obligation, ex-ante debt burden, unrated issuance, maturity, and bankruptcy access. The resulting pollution-related investment needs and a reduction in public sector employment and expenditure likely underlie the risk. An instrumental variable-like method utilizing airports as a potential contamination source reaffirms the causal interpretation.