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

Abstract

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 ewaste as their primary source. Domestic wastewater and sedimentary organic carbon content also significantly influenced 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.