Formation and contamination of PCDD/Fs, PCBs, PeCBz, HxCBz and polychlorophenols in the production of 2,4-D products

• PCDD/Fs, PCBs, HxCBz, PeCBz and polychlorophenols in 2,4-D were analyzed.
• Relationship between the precursors and UPPOPs was discussed.
• Emissions of PCDD/Fs and dl-PCBs in China were evaluated.
• A suggestion on 2,4-D production was developed to reduce UPPOPs emission.

The concentrations and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), pentachlorobenzene (PeCBz), hexachlorobenzene (HxCBz) and polychlorophenols in 2,4-D were investigated in this study. Two 2,4-D acid and three 2,4-D butyl ester enterprises were selected as typical 2,4-D producers. The total concentrations of 2,3,7,8-PCDD/Fs in the 2,4-D samples ranged from 355 to 35 080 ng kg−1 and the corresponding TEQ values were in the range of 13.4 and 694.6 ng WHO-TEQ kg−1. The concentrations of total PCBs in the 2,4-D were in the range of 16.1 and 8023 ng kg−1, and the WHO-TEQ values of the PCBs were between 0.057 and 108.3 ng WHO-TEQ kg−1, while total PCBs were between 1486 and 47 342 ng kg−1. The average emission factors were 414.4 μg WHO-TEQ t−1 for PCDD/Fs and 21.9 μg WHO-TEQ t−1 for PCBs. The polychlorobenzenes and polychlorophenols impurities may play a key role in the PCBs and PCDD/Fs formation. The impurities of PCDD/Fs and PCBs in 2,4-D may increase the risk for the human and environmental health.