Due to increasing regulations on the production and consumption of legacy per- and polyfluoroalkyl substances (PFAS), the global use of PFAS substitutes increased tremendously, posing serious environmental risks owing to their bioaccumulation, toxicity, and lack of removal strategies. This review summarized the spatial distribution of alternative PFAS and their ecological risks in global freshwater and marine ecosystems. Further, toxicological effects of novel PFAS in various freshwater and marine species were highlighted. Moreover, degradation mechanisms for alternative PFAS removal from aquatic environments were compared and discussed. The spatial distribution showed that 6:2 chlorinated polyfluorinated ether sulfonate (6:2 CI-PFAES, also known as F-53B) was the most dominant emerging PFAS found in freshwater. Additionally, the highest levels of PFBS and PFBA were observed in marine waters (West Pacific Ocean). Moreover, short-chain PFAS exhibited higher concentrations than long-chain congeners. The ecological risk quotients (RQs) for phytoplankton were relatively higher >1 than invertebrates, indicating a higher risk for freshwater phytoplankton species. Similarly, in marine water, the majority of PFAS substitutes exhibited negligible risk for invertebrates and fish, and posed elevated risks for phytoplanktons. Reviewed studies showed that alternative PFAS undergo bioaccumulation and cause deleterious effects such as oxidative stress, hepatoxicity, neurotoxicity, histopathological alterations, behavioral and growth abnormalities, reproductive toxicity and metabolism defects in freshwater and marine species. Regarding PFAS treatment methods, photodegradation, photocatalysis, and adsorption showed promising degradation approaches with efficiencies as high as 90%. Finally, research gaps and future perspectives for alternative PFAS toxicological implications and their removal were offered.
Perfluorooctanoic acid (PFOA) is a long-chain legacy congener of the per- and polyfluoroalkyl substances (PFAS) family, notorious as a "forever chemical" owing to its environmental persistence and toxic nature. Essential elements such as zinc (Zn) can cause toxic effects when they change their metal speciation and become bioavailable, such as zinc sulfate (ZnSO4). Combined toxicity assessment is a realistic approach and a challenging task to evaluate chemical interactions and associated risks. Therefore, the present study aims to elucidate the acute mixture toxicity (12-48 h) of PFOA and ZnSO4 in Daphnia magna at environment-relevant concentrations (ERCs, low dose: PFOA 10 μg/L ZnSO4 20 μg/L; high dose: PFOA 20 μg/L ZnSO4 50 μg/L) in terms of developmental impact, apoptosis induction, and interaction with major endogenous antioxidants. Our results showed that deformity rates significantly increased (p
Per- and polyfluoroalkyl substances (PFAS) are also known as "forever chemicals" due to their persistence and ubiquitous environmental distribution. This review aims to summarize the global PFAS distribution in surface water and identify its ecological and human risks through integrated assessment. Moreover, it provides a holistic insight into the studies highlighting the human biomonitoring and toxicological screening of PFAS in freshwater and marine species using quantitative structure-activity relationship (QSAR) based models. Literature showed that PFOA and PFOS were the most prevalent chemicals found in surface water. The highest PFAS levels were reported in the US, China, and Australia. The TEST model showed relatively low LC50 of PFDA and PFOS for Pimephales promelas (0.36 and 0.91 mg/L) and high bioaccumulation factors (518 and 921), revealing an elevated associated toxicity. The risk quotients (RQs) values for P. promelas and Daphnia magna were found to be 269 and 23.7 for PFOS. Studies confirmed that long-chain PFAS such as PFOS and PFOA undergo bioaccumulation in aquatic organisms and induce toxicological effects such as oxidative stress, transgenerational epigenetic effects, disturbed genetic and enzymatic responses, perturbed immune system, hepatotoxicity, neurobehavioral toxicity, altered genetic and enzymatic responses, and metabolism abnormalities. Human biomonitoring studies found the highest PFOS, PFOA, and PFHxS levels in urine, cerebrospinal fluid, and serum samples. Further, long-chain PFOA and PFOS exposure create severe health implications such as hyperuricemia, reduced birth weight, and immunotoxicity in humans. Molecular docking analysis revealed that short-chain PFBS (-11.84 Kcal/mol) and long-chain PFUnDA (-10.53 Kcal/mol) displayed the strongest binding interactions with human serum albumin protein. Lastly, research challenges and future perspectives for PFAS toxicological implications were also discussed, which helps to mitigate associated pollution and ecological risks.