The Effects of Cadereyta's Refinery Temporary Shutdown on Air Quality and Mortality

Oil refineries are a major source of pollution in the world. Their harmful effects on health have been studied mainly in developed countries within a short distance of their locations. These effects are usually attributed to primary emissions of sulfur dioxide. We use a regression discontinuity in time approach, harnessing an unforeseen 6-day shutdown at Cadereyta’s refinery, to study its impact on air quality and mortality in the downwind Monterrey´s Metropolitan Area (MMA). We find that, in addition to increasing local concentrations of sulfur dioxide, the refinery contributes with 30% of the concentrations of PM2.5 and PM10 in the MMA, up to 60 km away from the refinery. Moreover, it increases the number of daily deaths from internal causes in 2.4%. Hence, even if an emitted primary pollutant such as sulfur dioxide poses only a local risk, its subsequent conformation in secondary pollutant—as particulate matter—can travel long distances affecting areas which are apparently remote.