Short-, medium-, and long-chain chlorinated paraffins in sediments from the Pearl River Delta, China: Occurrence,...

Chlorinated paraffins (CPs), classified as short-, medium-, and long-chain CPs (SCCPs, MCCPs, LCCPs), are extensively used additives in plastics, rubbers, electronics, and metal-processing industries. Their high release potential, persistence, bioaccumulation, and toxicity have raised increasing global concern, particularly in urban and industrial areas. Although SCCPs and MCCPs have been regulated under the Stockholm Convention, significant knowledge gaps remain regarding MCCPs' environmental behavior and ecological risks, while LCCPs have been largely overlooked. This study investigated all three CP classes in sediments from the Pearl River Delta (PRD), a major industrial and economic hub in China. Total CP concentrations ranged from 40.9 to 2450 ng g^-1 dry weight (dw) (627 ± 523 ng g^-1 dw), representing moderate to elevated levels globally (range (median): 0.661-11,400 (200) ng g^-1 dw) and exceeding those of other typical flame retardants in the PRD. In composition, MCCPs predominated, with SCCPs and LCCPs at lower yet comparable levels, reflecting China's consumption profile. Spatially, sedimentary CPs showed elevated levels in industrialized/urbanized areas and significant correlations with industrial wastewater discharges and electronics-related industries. Traditional and upgraded commercial CP-52 mixtures were identified as the primary source contributors (> 60%), followed by legacy SCCP-containing products and CP-70-related materials such as ship paints. Although hazard quotients (HQs) of CPs were < 1 in most sediments, > 50% of samples showed moderate risk (HQ > 0.1) and one exceeded the threshold. SCCPs contributed most to total risk, followed by MCCPs and LCCPs. These findings provide a comprehensive overview of CP pollution profiles, sources, and ecological risks in a typical industrial region, highlighting the emerging concern of LCCP contamination.