Are histopathological endpoints useful for the evaluation of natural soils contaminated by metals and radionuclides?

Abstract

Purpose: The main objective of this study was to assess the sensitivity of histopathological endpoints, to be considered in the standard earthworm’s reproduction assay, performed to evaluate the ecotoxicological impact of soils contaminated with radioactive wastes. Methods: Eisenia andrei was exposed, for 56 days, to a contaminated soil from an abandoned uranium mine and to the natural reference soil LUFA 2.2. The organisms were sampled after 0, 1, 2, 7, 14 and 56 days of exposure, to assess metal’s bioaccumulation. The bioaccumulation of radionuclides, growth and the occurrence of histopathological alterations in the body wall and gastrointestinal tract, were also determined at 0, 14 and 56 days of exposure. The hematoxylin–eosin method was used to prepare slides for optic microscopy. Results of the study: Results have shown the bioaccumulation of metals and radionuclides, as well as, growth reduction in earthworms exposed to contaminated soil. Also after 14days,the exposure to the contaminated soil, caused alterations such as disorganization and deformation of the tissues analyzed (except for the intestinal epithelium). More severe effects, like atrophy, degradation and necrosis were observed after 56 days of exposure, in all the tissues analyzed. Here we demonstrate that histological changes in the body wall and gastrointestinal tract are important endpoints to be used in the earthworm reproduction assay, as part of the risk assessment of contaminated areas.