We develop a theoretical framework and present a corresponding empirical analysis of the Food and Drug Administration’s irrigation water quality regulatory standard under the Food Safety Modernization Act using lettuce as a case study. We develop a stochastic price endogenous partial equilibrium model with recourse to examine the standard’s efficacy under various scenarios of foodborne illness severity, standard implementation, demand response to foodborne outbreaks, and irrigation costs. The stringency of regulation is evaluated with endogenous producer response to regulatory requirements and corresponding implications for economic surplus. The baseline results show that in the case of the lettuce market, the proposed microbial irrigation water quality regulation in the Food Safety Modernization Act (FSMA) is not cost effective relative to the existing Leafy-Greens Marketing Agreements relying on water treatment for mitigation of microbial contamination. However, FSMA can be cost effective if water treatment is sufficiently expensive.