Emission Changes of PCDD/Fs in the Iron and Steel Industry under Ultra-Low Emission Transformation
China's iron and steel industry has undergone comprehensive ultra-low emission transformation, meeting stringent limits for conventional pollutants, yet the fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) remains unclear. This study combined field sampling and literature review to analyze PCDD/Fs emission characteristics from sintering, converter, and electric arc furnace processes before and after transformation, and calculated national emissions for 2022. Results demonstrate that ultra-low emission transformation effectively reduces PCDD/Fs emissions. Specifically, emission concentrations decreased by 86.5%, 95.1%, and 66.9% for sintering, converter, and electric arc furnace, respectively, with corresponding emission factors dropping to 0.11, 0.009, and 0.014 μg I-TEQ·t−1 product. Under the transformation scenario, total national emissions were 104 g I-TEQ (uncertainty ±26 g), a 94.9% reduction from the unreformed scenario (2049 ± 763 g I-TEQ). Congener profiles shifted from high-chlorinated dominance to low-chlorinated dominance, while toxicity equivalent distribution remained dominated by 2,3,4,7,8-PeCDF (35%–56%). This study quantifies the co-benefit of PCDD/Fs reduction, providing critical data for updating China's emission inventory and formulating toxicity-oriented control policies.