Correlation analysis among target polymers, polypropylene (PP), and three halogenated flame retardant (HFR) groups at the plastic recycling plant (PRP). The HFR groups included ∑4 novel brominated flame retardants (NBFRs; PBEB, HBB, BTBPE, and DBDPE), ∑8 polybrominated diphenyl ethers (PBDEs; BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, and BDE-209), and ∑2 dechlorane plus isomers (DPs; syn-DP and anti-DP).