Uptake of palladium by the fauna

Abstract

Since 1985 the total global demand of the platinum group metals (PGM) Pt, Pd and Rh has doubled with a still increasing tendency. In 2004 the total global demand of Pd was 191 t, with 114 t being used in the autocatalyst sector (Johnson Matthey 2004). As a consequence of the growing use of Pd, elevated Pd concentrations were found in different environmental matrices such as airborne particulate matter, road dusts and soils along heavily frequented roads (summarized in e.g. Zereini and Alt 2000, Hoppstock and Sures 2004). Besides of terrestrial ecosystems, Pd is also introduced into aquatic habitats. Depending on the age and type of the catalytic converter the emission rate of an individual car is up to 50 ng Pd per km (Moldovan et al. 2002). The platinum group metals are emitted attached to aluminium oxide particles, mainly in the oxidation status of zero or as oxides (Moldovan et al. 2002). Therefore, it may be assumed that PGM behave in an inert manner and are immobile in the environment. But solubility studies with automobile exhaust fumes and road dusts revealed that Pd emitted from cars is at least partly soluble and therefore mobile (Moldovan et al. 1999 & 2002, Palacios et al. 2000, Jarvis et al. 2001). Accordingly, the effects of increasing PGM emissions on the biosphere are more and more controversially discussed (Zimmermann and Sures 2004). One of the main results of recent research is the proof that PGM are biologically available. As biological availability is one of the most decisive factors determining the toxicological potential of xenobiotics, this information is very important to evaluate the possible threat of the noble metals to ecosystems. Unfortunately, there are only few studies on the biological availability of Pd since the determination of Pd is usually more challenging than the analysis of Pt and Rh. Furthermore, metal determination in animal tissues often requires very sensitive techniques as the sample amount of animals is generally restricted. This chapter summarizes the limited data on the biological availability, uptake and accumulation of Pd for animals and emphasizes the lack of knowledge where research has to be done.