Fish biomonitoring in coastal lagoons: Assessing air-to-water contamination by metallurgical industry, neurotoxicity, and nanoparticle uptake

Metallurgical industries release settleable particulate matter (SePM), contaminating aquatic ecosystems with metal(loid)s and metallic nanoparticles (NPs). This study analyzed 27 metal(loid) and acetylcholinesterase (AChE) activity in the brain and muscle of Oreochromis niloticus following 96 h exposure to 0.0 (T0-control), 0.01 (T1), 0.1 (T2) and 1.0 (T3) g L -1 of SePM and in specimens collected in 2021 and 2022 from two coastal lagoons (Carapebus and Maembá) near metallurgical industries, and an aquaculture facility (Alegre) in Brazil. In the brain, the highest concentrations (mean ± SEM, μg g⁻¹) were Fe (500.98 ± 6.37), Al (254.57 ± 2.02), Ag (98.65 ± 0.15), Zn (67.13 ± 0.64), and Sn (35.18 ± 2.07). In the muscle, Se (49.57 ± 4.23), Zn (37.76 ± 3.46), Fe (29.71 ± 0.87), Rb (27.26 ± 0.89), and Sn (16.61 ± 0.09) predominated. Ultrastructural analysis confirmed NPs containing Fe, Al, Cu, Ti, and Sn in both tissues. While 96 h SePM exposure did not alter AChE activity, field data revealed significant variations: in 2021, Carapebus fish showed significantly lower AChE in brain and muscle. In 2022, Maembá showed elevated brain AChE activity. Spearman analysis revealed positive correlations between AChE and Cu, Zr, Sn, and Pb, and negative correlations with V, Mn, Ni, W, Fe, Se, and Cr. These findings demonstrate that the brain is a more sensitive target for AChE inhibition than muscle. Although laboratory results did not fully reflect field neurotoxic patterns, AChE remains an effective biomarker for monitoring atmospheric PM impacts on aquatic biota.