Occurrence, sources, and risks of short-, medium-, and long-chain chlorinated paraffins in sediments from an e-waste...

Chlorinated paraffins (CPs), widely used in plastics, metalworking fluids, coatings, and lubricants, have raised growing environmental concerns due to their persistence, long-range transport potential, bioaccumulation, and toxicity. Both short- and median-chain CPs (SCCPs and MCCPs) are regulated under the Stockholm Convention. Although e-waste is a major CP source, the environmental behavior and risks of CPs, particularly MCCPs and long-chain CPs (LCCPs), remain poorly characterized in recycling areas. We analyzed all three CP classes in sediments from China's Lian River, which flows through Guiyu, a major e-waste recycling hub. Total CP concentrations (90.0-9 980 ng g^-1) were moderate globally and relative to other flame retardants in the same river. CP levels showed a clear spatial pattern: lowest at headwaters, highest around Guiyu, and declining downstream, identifying e-waste as their primary source. Domestic wastewater and sedimentary organic carbon content also significantly influenced the CP distribution. Source analysis revealed that imported e-waste and China's CP-52 products contributed over 50% of the river's CP burden, followed by SCCP-containing products/waste (13-29%) and domestic CP-70 applications (8-33%). Hazard quotient (HQ) results indicated acceptable ecological risk (HQ < 1) at all sites except two in Guiyu. SCCPs showed the highest HQs despite intermediate concentrations; MCCPs contributed the most mass but intermediate HQs; and LCCPs exhibited the lowest concentrations and risks. These findings provide the first comprehensive pollution and risk assessment of all CP classes along a sediment transect encompassing an e-waste recycling zone, providing critical insights into emerging LCCP contamination.