Metal-rich particulate matter inhibits acetylcholinesterase activity in the brain of native estuarine fish Centropomus parallelus

Industrial activities in coastal areas release metal-rich settleable particulate matter (SePM), raising concerns about neurotoxic risks to aquatic organisms. This study exposed the neotropical native estuarine fish Centropomus parallelus to three SePM concentrations (0.01 - T1, 0.1 - T2, and 1.0 g L^-1 - T3) for 96 h to evaluate brain bioaccumulation, acetylcholinesterase (AChE) activity, and nanoparticle (NP) uptake. Metal/metalloids concentrations were determined by ICP-MS, and transmission electron microscopy (TEM) was used to identify internalized NPs. From 27 metal/metalloids analyzed, seventeen were quantified, including V, Cr, Mn, Fe, Ni, Cu, Rb, Sr, Mo, Ag, Hg, and emerging elements such as Ce, Nb, Ti, W, Y, and Zr. Chromium, Fe-, and Mo-based NPs were detected in neural cell cytoplasm, and particles enriched in W, Fe, V, Cr, and Mo were observed in the SePM. AChE activity was significantly inhibited at the highest dose. Multivariate and correlation analyses revealed distinct accumulation patterns, particularly at the highest exposure, and negative associations between Ni, Rb, Sr, Cr, Cu and Zr and AChE activity. These results indicate that SePM induces early neurotoxic responses in C. parallelus and disrupts the cholinergic system. SePM particles containing Cr, Fe, W, V, and Mo may be consistent to metallurgical sources. Significant correlations among these metals and the detection of Cr-, Fe-, and Mo-based NPs in fish brain tissue demonstrate environmental transfer and biological uptake of particles consistent with metallurgical emission. This highlights the need for stricter control of industrial particulate emissions to safeguard estuarine ecosystems.