Histopathological and Bioaccumulation Assessment of Surfactants (NPE and LAS) in Freshwater Fishes Using GC–MS Analysis

Abstract

Nonylphenol ethoxylates (NPE) and linear alkylbenzene sulfonate (LAS) serve as surfactants whose production exceeds 1000 metric tons yet scientists find them in all freshwater ecosystems because wastewater treatment systems fail to remove them completely. The lipophilic metabolites of NPE degradation, especially nonylphenol (NP), present severe risks to ecological systems. The research examined how NPE/LAS pollutants accumulate in organisms and their subsequent impact on Labeo rohita (rohu) fish through histopathological testing. The fish received three sublethal concentrations (0.1, 0.5, and 1.0 mg L⁻¹) of a commercial NPE mixture and LAS for 28 days. Researchers used Gas Chromatography–Mass Spectrometry (GC–MS) to examine liver, kidney, gill, and muscle tissue samples for NP and LAS residues. The researchers assessed histopathological changes that occurred in gill, liver, and kidney tissues. The GC–MS analysis showed that NP, which acts as the persistent metabolite of NPE, accumulated in liver and kidney tissues at significant levels that increased according to the administered dose. The examination showed LAS to have lower accumulation levels which remained detectable. The histopathological examination discovered extensive tissue damage which progressed according to the dose consumed by the subjects. The study found a direct relationship between tissue NP residue levels and histopathological severity assessment. The research proves that freshwater fish experience major organ harm through chronic exposure to NPE at levels found in their natural environment because NP bioaccumulation leads to various health problems which affect their ability to function and survive. The tissue stress from LAS showed lower accumulation levels than other substances. The research demonstrates that environmental surfactant discharge requires strict regulation because environmental monitoring benefits from combined bioaccumulation (GC–MS) and biomarker (histopathology) assessment methods.