Substantial Emission Reductions from Chinese Iron- and Steelmaking after the Introduction of Ultralow Emission Standards during the Prepandemic and Midpandemic Periods

China’s iron and steel industry has achieved notable progress in reducing pollution following the implementation of ultralow emission (ULE) standards. However, the extent of pollutant reduction, compliance with ULE standards, and influencing factors, particularly during the prepandemic and midpandemic periods, remain insufficiently explored. In this study, high-resolution, nationwide, process-based, and facility-level emission inventories for China’s iron and steel industry for 2018–2020 were developed on the basis of real-time measurements from Continuous Emission Monitoring Systems (CEMS). The emission inventories covered air pollutant emissions from 996 iron and steel enterprises, accounting for 87.98 to 96.43% of China’s crude steel production between 2018 and 2020, and encompassed key production processes, including coking, sintering, pelletizing, blast furnaces, basic oxygen furnaces, electric arc furnaces, and steel rolling. Compared to 2018, emissions of SO2, NOx, and PM from the iron and steel industry in 2020 decreased by 32.56, 47.02, and 9.05%, respectively, despite a 14.74% increase in production. Furthermore, average hourly concentration compliance rates for SO2, NOx, and PM at the sintering machine head, sintering machine tail, and pellet roasting showed significant improvement in 2020. Structural equation modeling identified product output, emission factors, ULE standards, and emission intensity as the key determinants of pollutant emissions. This study highlighted the necessity of strengthening the implementation of ULE standards in regions and fostering regional cooperation for emission reduction.