Multigeneration responses of the springtail <i>Folsomia candida</i> to short-chain per- and polyfluorinated substances

Short-chain per- and polyfluorinated substances (PFAS) are widely distributed in the environment, but their chronic effects on soil organisms exposed over multiple generations remain largely unknown. The present study therefore aimed to investigate the toxicity of perfluorobutane sulfonic acid (PFBS) and its precursor perfluorobutane sulfonamide (FBSA) to the springtail Folsomia candida during five successive generations with the following endpoints: the median lethal concentration (LC50) for adult survival and the median effect concentration (EC50) for reproduction (EC50_repro) and population growth rate (EC50_r). The LC50 and EC50_r of PFBS were above the highest test concentration (1,300 mg/kg dry soil) for all generations, while the EC50_repro was 1,260 and 762 mg/kg dry soil in F2 and F4 (i.e., third and fifth generations), respectively, although the difference was not significant owing to wide 95% confidence intervals. In contrast, FBSA exhibited significant reproductive toxicity and thereby affected the population growth rate, with LC50, EC50_repro, and EC50_r values of 10.3, 1.14, and 1.67 mg/kg dry soil in F0. The extinction of the populations exposed to the two highest FBSA concentrations (8.85 and 88.3 mg/kg dry soil) in F0 hindered toxicity assessment in subsequent generations, with only an EC50_repro of 0.965 mg/kg dry soil determined in F1. Although the effect concentrations were above environmental levels, the more pronounced reproductive toxicity made FBSA >1,140 and >1,350 times more toxic to F. candida reproduction than PFBS in F0 and F1. These findings reveal that understudied PFAS may pose hidden risks, thus emphasizing the need to expand the currently limited spectrum of PFAS considered in environmental risk assessment. This study also highlights the value of long-term hazard assessment of PFAS in multigeneration scenarios, which could better capture the potential risks posed by these very persistent chemicals.