Abstract
<title>Abstract</title> <p>Long-standing emission control policies may become less cost-effective and warrant reassessment as technologies and knowledge of atmospheric chemistry evolve. This issue is particularly important for California, which faces persistent summertime ozone nonattainment and the highest gasoline prices in the United States. Since the 1990s, California has adopted stringent summer gasoline volatility limits to control ozone, which increase gasoline production costs and prices, yet their air quality impacts under present-day conditions remain unclear. Emissions modeling indicates that replacing summer-blend gasoline with higher-volatility winter-blend gasoline would increase statewide anthropogenic reactive organic gas emissions by 2.7% in July and 1.1% in October. High-resolution air quality simulations show population-weighted maximum daily eight-hour average ozone increases of 0.075 ppb (0.14%) and 0.006 ppb (0.01%) in July and October, respectively, while the changes in PM2.5 are negligible. Winter-blend gasoline organic gas emissions are less reactive, partially offsetting and even overturning air quality penalties predicted from volatility alone. Estimated monthly production-cost savings of US$70–73 million, with potentially larger consumer savings, exceed monetized health effects. These findings demonstrate the value of integrated air quality, health, and economic assessment in informing environmental regulations.</p>