Bioaccumulation trends of microplastics and trace metals in Oreochromis niloticus: A health risk assessment in an urban coastal lake, India.

Accumulation within fish tissues establishes these organisms as valuable bio-indicators for monitoring environmental health and potential food safety risks. This research represents the pioneer study investigating microplastic and trace metal accumulation within the muscle tissues of edible fish from the urban Veli-Akkulam lake in Thiruvananthapuram. The research evaluated the microplastics and concentration of trace metals such as Hg, Fe, Zn, Pb, Cr, Cu, Mn, Co, Ni, and Cd alongside malondialdehyde (MDA) content in the tissues of Oreochromis niloticus. To evaluate spatio-temporal variations across 5 stations and 3 seasons, independent biological replicates were sampled: 45 fishes for baseline MDA metrics and a coupled subset of 30 fishes for parallel trace metal and microplastic tracking. Individual data were aggregated into 15 independent spatio-temporal groups (N = 15) for Pearson correlation and Multiple Linear Regression (MLR) analyses. Macro-level modeling revealed widespread MP accumulation, primarily blue fibers, with polycarbonate identified as a "Category IV" polymer. Concentrations of Mn and Cr in edible tissue consistently exceeded FAO/WHO safety limits of 1 mg/kg and 0.05 mg/kg, respectively. While both contaminants are prevalent, MLR indicated that trace metal accumulation, rather than microplastics presence, displayed a stronger statistical coupling with elevated MDA levels (reaching 0.54 ± 0.041 µmol/mg). Consequently, human exposure models suggest seasonal variations in dietary risk parameters, while the Hazard Index (HI) remained safely below 1; target cancer risk for Cr and Ni pointed to elevated risks during the monsoon season, underscoring the necessity for localized pollution monitoring.