Long-term dynamics and circularity implications of brominated flame retardants in China's plastics

Plastic circularity is increasingly promoted, yet hazardous legacy additives may persist and recirculate within secondary material flows, undermining both environmental safety and circular-economy benefits. Brominated flame retardants (BFRs) are widely incorporated into plastics, but their long-term national-scale flows, emissions, and climate implications remain poorly understood. Here, we integrate dynamic material flow analysis with life cycle carbon footprint to quantify BFRs-containing plastics in China from 1978 to 2022 across five major commodity plastics. Results show a marked transition from stock accumulation to higher-throughput circulation. BFR consumption reached 1768.81 kt in 2022, while in-use stocks increased to 15,993.45 kt, mainly concentrated in building and construction and electronics. Cumulative generation of BFRs-containing plastic waste reached 8806.98 kt over 1978-2022. Total BFR emissions were estimated at 110.11 kt, partitioning mainly to soils (61.65%), followed by water (28.03%) and air (10.32%). Production and manufacturing dominated releases, contributing 79.39% of total emissions, while regulated end-of-life management reduced uncontrolled disposal but also increased the potential for additive recirculation through recycling. The cumulative life-cycle carbon footprint of plastics and BFRs reached 6555.42 Mt CO₂-eq, increasing from 5.6 Mt in 1978-493.5 Mt in 2022. Scenario results further indicate that increasing recycling intensity does not continuously improve environmental performance, because BFR emissions persist while carbon benefits rapidly approach saturation beyond a moderate circulation range. These findings show that safe plastic circularity requires additive-aware management, including traceability, selective recycling, and controlled treatment of high-BFR fractions, to balance resource recovery with chemical safety and climate mitigation.