Following the bioaccumulation and toxicity of 1.0 ppm sublethal doses of platinum group metals in developing chick embryo tibiotarsi

Abstract

<p>Platinum group metals (PGMs) such as palladium, rhodium, and platinum have been shown to accumulate in living organisms due to emission by catalytic car converters at traffic sites. Unfortunately, little is known about their toxicity. Our previous studies showed that chick embryos exposed to PGM concentrations of 5.0 ppm (LDso) and higher presented skeletal deformities and anomalous calcium inclusions within the brain tissue. In this study, the bioaccumulation of 1.0 ppm sublethal PGM doses within the bone tissue of developing chick embryos was determined by inductivelycoupled plasma optical emission spectroscopy (lCP-OES). The average calcium content and its distribution, which reflect the bone development process within tibiotarsi, were established by flame atomic absorption spectroscopy (FAAS) and X-Ray fluorescence spectroscopy (XRF), respectively. Chick embryos were injected with 1 mL of 1.0 ppm Pd(II), pt(IV), Rh(II') aqueous salt solutions and a PGM mixture on the i h and 14th days of incubation. Control groups with no-injection and 1 mL injections of saline solutions were included. Embryos were sacrificed on the 20th day and tibiotarsi were harvested. Tibiotarsi for FAAS and ICP-OES analysis were dehydrated overnight, chemically digested, and quantitatively diluted in 2% nitric acid. Tibiotarsi for XRF analysis were sectioned longitudinally and mounted on the sample holder. ICP-OES measurements showed that PGM concentrations in tibiotarsi were below the instrument's detection levels. FAAS analysis revealed that the calcium content increased by 54% in the Pd treatments and decreased by 57% in the Pt treatments. Such extreme changes lead to bone tissue hardness or brittleness. The Rh and PGM treatments caused no significant changes when compared to the no-injection control samples (i.e. 17.05%). XRF images illustrated abnormal calcium distribution within the inner and outer longitudinal sections of tibiotarsi and confirmed the FAAS results. In particular, the PGM treatment sample manifested abnormal calcium deposits within the bone marrow cavity of tibiotarsi. In conclusion, the FAAS, ICP-OES, and XRF data showed that exposure of chick embryos to 1.0 ppm sublethal doses of PGMs disrupted their calcium metabolism and bone development.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 8, 2011</p>