Battery-type-associated pollutant fingerprints and cytotoxicity of firefighting wastewater from full-scale electric vehicle fires.

The rapid adoption of electric vehicles (EVs) has increased concern over fires, whose suppression generates chemically complex wastewater. However, the temporal evolution and toxicity of EV fire wastewater remain poorly understood. In this study, we conducted full-scale fire and suppression tests on EVs powered by nickel-manganese-cobalt (NMC) and lithium iron phosphate (LFP) batteries, using time-resolved sampling to characterize firefighting runoff and residual wastewater retained after suppression. By integrating chemical profiling and in vitro cytotoxicity assays, we resolved battery-type-associated wastewater hazards. Runoff wastewater exhibited distinct metal-release fingerprints: NMC-runoff carried substantially higher battery-derived ionic loads, with early-stage Li+ reaching 4.26-4.59 mg·L-1, approximately one order of magnitude higher than that in LFP-runoff (averaging 0.36 mg·L-1). Residual pallet wastewater acted as a concentrated pollution reservoir, with NMC samples becoming strongly alkaline (pH>11). Li+ and fluoride in residual wastewater reached about 7.21 × 102 mg·L-1 and 3.85×102 mg·L-1, respectively, generally more than two orders of magnitude higher than in runoff wastewater. Cytotoxicity tests revealed that residual wastewater induced concentration-dependent cytotoxicity, with human neuroblastoma cells being the most sensitive and viability decreasing to 5.7%. These findings identify residual or immersion-type suppression water as a secondary EV fire hazard and support battery-type-specific strategies for emergency management. SYNOPSIS: Full-scale NMC and LFP battery EV fire tests reveal distinct wastewater pollutant fingerprints, sludge properties, and cytotoxic profiles, underscoring the need for chemistry-specific environmental standards and emergency protocols.