Platinum Group Metals: The Toxic Catalysts

Platinum Group Metals (PGM), such as platinum (Pt), palladium (Pd), and rhodium (Rd), are of increasing concern due to rising anthropogenic input to aquatic systems. In this study, PGMs’ effects on bioaccumulation and histopathological changes were investigated using Orconectes virilis, a native species of the Hudson River, as a model. Organisms were exposed to varying concentrations of water-soluble PGM salts for ten days. The following experimental treatments were established: 0.0, 1.0, 5.0, 10.0 ppm Pt(IV), 1.0 ppm Rh(III), 1.0 ppm Pd(II), and a PGM Mix (1.0ppm Pt(IV), Rh(III), Pd(II) each) dissolved in raw Hudson River water. Metal content in the tissue samples were analyzed by SPECTRO GENESIS ICP-OES. SPSS statistical package was used to analyze Pt, Pd, and Rh content in different treatments and behavioral changes during the experiment. Paraffin sections, 6 µm thick, were prepared in E&H stain and examined for histological abnormalities within the liver, exoskeleton, brain, and ganglia. Statistically significant differences in bioaccumulation of PGMs were observed in all organs, with highest concentrations found in liver tissue, 816.83 μg/0.1g dw for1.0 ppm Pd treatment, 200.33 μg/0.1g dw Rh for 1.0 ppm Rh treatment, and 815.83 μg/0.1g dw Pt for the 5.0 ppm Pt treatment. Platinum content was significantly lower at the 10 ppm exposure, suggesting severe structural damage to the tissue. Hyper-segmentation of vacuoles and swelling of the vascular channels were observed in the hepatocyte structure of the liver. Exoskeletal tissue showed visible bands in the exocuticle indicating demineralization, while the brain and ganglia demonstrated extensive vacuolization. Behavioral analysis showed a significant increase of maximum response intensity over the experimental period within each treatment. Bioaccumulation and cellular abnormalities observed in exposed aquatic organisms raise concern of PGM bio-magnification within the food chain and its effect on the environment and human health.