Specific Objectives of the Project
• Statistically describe the spatial and temporal distribution of pesticide use in Californian agriculture.
• Estimate the effect of pesticide applications on local air quality (PM2.5)
• Estimate human population exposure to pesticides through air.
Future work: Estimate the effect of pesticide use in Californian agriculture on health outcomes.

Project Report/Summary of Results
Many policymakers, public-health advocates, and citizen groups question whether current pesticide regulations properly equate the marginal social costs of pesticide applications to their marginal social benefits—with particular concern for negative health effects stemming from pesticide exposure. Additionally, recent research and policies in public health, epidemiology, and economics emphasize how fine particulate matter (PM2.5) concentrations harm humans through increased mortality, morbidity, mental health issues, and a host of socioeconomic outcomes. This paper presents the first empirical evidence that aerially applied pesticides increase local PM2.5 concentrations. To causally estimate this effect, I combine the universe of aerial pesticide applications in the five southern counties of California's San Joaquin Valley (1.8MM reports) with the U.S. EPA's PM2.5 monitoring network—exploiting (1) spatiotemporal variation in aerial pesticide applications and (2) variation in local wind patterns. I find significant evidence that (upwind) aerial pesticide applications within 1.5km increase local PM2.5 concentrations. The magnitudes of the point estimates suggest that the top decile of aerial applications may sufficiently increase local PM2.5 to warrant concern for human health.