Mysterious emissions of Halon-2402 in eastern Asia drive the global trend

1,2-Dibromotetrafluoroethane (C₂Br₂F₄, Halon-2402, H-2402) is used as a fire suppressant due to its stability because it maintains a liquid state at room temperature with a relatively high boiling point. However, H-2402, containing bromine (Br), was identified as a potent ozone-depleting substance, with a destructive capacity six times higher than that of CFC-11. Therefore, under the Montreal Protocol, its production and consumption were phased out globally in 2010, with developed countries starting their phase out in 1994. Russia, the primary producer of H-2402, reportedly ceased production after 2000. For essential uses where no alternatives are available (e.g., military fire extinguishers, oil and gas pipelines), existing or recycled supplies of H-2402 are permitted to be used. Despite H-2402 being under strict international regulation, accurate reporting and statistical information on essential production and consumption by countries remain limited.

This study analyzes the atmospheric mole fractions records of H-2402 measured from 2008 to 2020 at Gosan station, South Korea. While the background mole fractions of H-2402 at Gosan station are gradually decreasing at -0.01 ppt/yr, similar to the global decreasing trend, high pollution cases were continuously observed throughout the entire period. Also, the frequency of occurrence also increased by more than three times in 2020 compared to 2008. This increase in pollution signals, not observed at major Northern Hemisphere background monitoring stations (such as Mace Head, Trinidad Head, and Jungfraujoch), suggests potential regional emissions in eastern Asia. Based on long-term atmospheric observations, and a combined analysis using the Lagrangian particle dispersion model (FLEXPART) and the Bayesian inverse framework (FLEXINVERT+), we have estimated the annual regional emissions in eastern Asia. We present observation-based results on the long-term, regional-scale variability of H-2402 emissions over eastern Asia and their significant contributions from a global perspective.