Ecotoxicology and Environmental Safety ] (]]]]) ]]]–]]] Platinum, palladium and rhodium release from vehicle exhaust catalysts and road dust exposed to simulated lung fluids Claudia Colombo à , A. John Monhemius, Jane A. Plant Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK Received 8 August 2007; received in revised form 18 November 2007; accepted 30 November 2007 Abstract The risk associated with the inhalation of platinum group element (PGE) emissions from vehicle exhaust catalysts (VECs) has been investigated by extracting road dust and milled auto catalyst with simulated lung fluids. Gamble’s solution (representative of the interstitial fluid of the deep lung) and artificial lysosomal fluid (ALF) (representative of the more acidic environment within the lung) were employed as extraction fluids. The highest PGE release was observed in ALF, implying that inhaled particles would have to be phagocytized before significant amounts of PGEs dissolve. The greatest percentage (up to 88%) of PGEs was released from road dust, possibly due to the presence of mobile PGE species formed in the roadside environment. Pt showed the highest absolute bioavailability, due to its greater concentration in the environmental samples. Pd and Rh had higher percentage of release, however, because of their more soluble nature. From the toxicological perspective, the results demonstrate potential health risks due to the likely formation of PGE-chloride complexes in the respiratory tract, such species having well-known toxic and allergenic effects on human beings and living organisms. r 2008 Elsevier Inc. All rights reserved. Keywords: Platinum; Palladium; Rhodium; Environment; Simulated lung fluids; Health risk 1. Introduction Human exposure to particulates from traffic is of increasing importance. There have been several studies of the concentrations of platinum (Pt), palladium (Pd) and rhodium (Rh) in airborne samples at different urban sites and working places following the increased use of vehicle exhaust catalysts (VECs) (Alt et al., 1993; Gomez et al., 2001; Zereini et al., 2001; Bocca et al., 2004; Ravindra et al., 2004). Platinum group elements (PGEs) are emitted in the exhaust gas from VECs with emission rates in ng/km range and their concentrations in urban air have increased by more than two orders of magnitude in the last 20 years (up to approximately 110 pg/m 3 , Merget and Rosner, 2001). PGE emissions are thought to occur mainly as fine particulate material that originates from the abrasion and deterioration of the surface of the catalyst. The results of direct determinations indicated that most of the PGEs released from VECs were in particulate form (Pt495%, Pd485% and Rh490%) (Konig et al., 1992; Moldovan et al., 1999, 2002). Furthermore, X-ray photoelectron spectroscopic studies (Schlogl et al., 1987) showed struc- tures very similar to that of pure Pt surface oxidized in a stream of oxygen. Such oxidized species of Pt could easily be mobilized by complexation (Nachtigall et al., 1996). Research into the size distribution of the PGEs emitted from modern three-way VECs (Artelt et al., 1999b; Merget and Rosner, 2001; Gomez et al., 2002) showed that the size fraction of particles with a diameter 410.2 mm ranged from ca. 43% to 71% and was thus the dominant fraction. Studies of particulate matter in urban areas in Germany (Alt et al., 1993) showed that Pt was present mainly in the small particle size fraction (0.5–8 mm), and its water soluble proportion varied from 30% to 43%. The determination of the size of the PGE particles emitted from VECs and contained in airborne dust is also important because size can influence solubility: ultra-fine particles are more soluble than larger particles. Studies on VEC emissions ARTICLE IN PRESS www.elsevier.com/locate/ecoenv 0147-6513/$ - see front matter r 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.ecoenv.2007.11.011 à Corresponding author. Fax: +44 207 594 7444. E-mail addresses: claudia.colombo@ic.ac.uk, claudia.colombo@imperial.ac.uk (C. Colombo). Please cite this article as: Colombo, C., et al., Platinum, palladium and rhodium release from vehicle exhaust catalysts and road dust exposed to simulated lung fluids. Ecotoxicol. Environ. Saf. (2008), doi:10.1016/j.ecoenv.2007.11.011