Comparing the Toxicity of Water-Soluble Fractions of Biodiesel, Diesel and 5% Biodiesel/Diesel Blend on Oreochromis niloticus Using Histological Biomarkers.

This study estimated end compared the potential toxic effects of the water-soluble fractions (WSF) of biodiesel (B100), diesel and the commercial biodiesel (B5) on Oreochromis niloticus. After a 24 h-exposition to WSF-0% (control) and WSF-serial concentrations of 4.6%, 10%, 22%, 46% and 100%, samples of gill and liver of the exposed fishes were fixed in Bouin's solution, processed, stained using hematoxylin/eosin and analyzed by light-microscopy. WSF-hydrocarbons and methanol contents, analyzed by gas chromatography, were checked against the occurrence of abnormal histopathological alterations. These were not found in the control and WSF-4.6% exposed fishes, while exposures to or above 10%-WSF resulted in histopathological alterations whose severity increased in a dose-dependent manner, being higher in fishes exposed to WSF-diesel, or WSF-B5 when compared to biodiesel. These results, which were corroborated by the chemical analyses, highlighted the histological technique as an appropriate diagnostic tool that can be used for the preservation of water bodies' quality.