Leachability of per- and polyfluoroalkyl substances in metal recycling streams

Automotive shredder residue (ASR), the remaining waste after vehicles and other metal recycling streams have been recycled, has been identified as a potential long-term per- and polyfluoroalkyl substance (PFAS) waste stream. However, the types, quantities, and potential leachability of PFAS in ASR are largely unknown. We quantified 33 targeted PFAS and extractable organic fluorine (EOF) in 15 ASR solid samples along with corresponding water-leachable measurements. The sum of targeted PFAS concentrations in ASR solids ranged from 9.4 to 104.2 ng/g and was dominated by long-chain perfluorinated alkyl acids (PFAAs). In contrast, short-chain PFAAs were most susceptible to leaching, resulting in aqueous targeted PFAS concentrations of 106.8 to 1015.1 ng/L. On average, 76 % of perfluorooctanoic acid (PFOA) and 15 % perfluorooctane sulfonate (PFOS) were water-leachable from ASR. EOF results indicated on average > 99 % of organic fluorine in the ASR solid samples was undetected in the targeted PFAS results, demonstrating that targeted PFAS analysis underestimates the amount of organic fluorine in ASR. Results from this study indicate that ASR can leach PFAS under some conditions, which has implications for the mobility of these chemicals in stormwater and landfill systems.