Impact of Platinum Group Metals on the Environment: A Toxicological, Genotoxic and Analytical Chemistry Study

Recent studies show particles of Platinum Group Metals (PGMs); primarily platinum, palladium and rhodium; released from automobile catalytic converters are being deposited alongside roadways. This deposition is leading to increasing concentrations of PGMs in the environment, raising concerns about the environmental impact and toxicity of these elements in living organisms. The objective of this study was to determine how PGMs alter the patterns of growth, development, and physiology by studying the toxicological and genotoxic effects of these metals. Two vastly different species were used as models: plant—a wild wetland common Sphagnum moss, and animal—6-week old rats Sprague–Dawley. Both species were exposed, in controlled environments, to different concentrations of the PGMs. Toxicological and genotoxic effects were determined by assessment of plant growth, animal survival and pathology, and influence on DNA in both models. Our results on the uptake of PGMs by Sphagnum showed significant decreases in plant length and biomass as PGM concentration increased. Histological and pathological analysis of the animal model revealed vacuolization, eosinophil inclusion bodies in adrenal glands, shrinkage of glomeruli in the kidney, and enlargement of white pulp in the spleen. In both models, DNA damage was detected. Chemical analysis using ICP-AES atomic absorption demonstrated accumulation of PGMs in plant tissues at all PGM levels, proportional to concentration.

Key Words:

• Platinum Group Metals
• Platinum
• Rhodium
• Palladium
• Pathology
• DNA damage.

Notes

*The initial plant length was 6 cm. Values represent the mean value of 30 replicates ± standard deviation. Sphagnum lengths in different treatments with the same letter ^{(a, b, c, d, e)} were not significantly different at the 0.05 probability level, as determined by the Student–Newman–Keuls multiple-comparison test. Significance between the PGM mix* treatment and control was compared using T-test paired two samples for means at α < 0.05.

**PGM mix contained Pt, Rh, and Pd salts in the concentration 0.1 ppm of each metal.

*The values in the table represent comet tail length mean ± standard deviation in μm for 50 nuclei per sample for each of three replicates. Values with the same letters^{(a, b, c, d)} comparing treatments for Pt, Rh and Pd were not significantly different at probability level α < 0.05 as determined by one-way analysis of variance with the Student–Newman–Keuls multiple-comparison test. Significance between the PGM mix* treatment and control was compared using t-test paired two samples for means at α < 0.05.

**PGM mix contained Pt, Rh, and Pd salts in the concentration 0.1 ppm of each metal.

*AF accumulation factor was computed by comparison amount of PGMs in plant tissue determined by atomic absorption and amount added to the standard media in the cultures (Std).

^†PGM mix contained Pt, Rh, and Pd salts in the concentration 0.1 ppm of each metal.

*PGM mix contained Pt, Rh, and Pd salts in the concentration 0.1 ppm of each metal.

**Comet length means ± SD are average length of 70 nuclei per sample from each of the three replicates. Comet lengths with the same letter ^{(a, b, c, d)} were not significantly different at α < 0.05 probability level, as determined by the Student–Newman–Keuls multiple-comparison test.