Platinum, palladium and rhodium release from vehicle exhaust catalysts and road dust exposed to simulated lung fluids

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.

Comparison of the extraction efficiencies of different leaching agents for reliable assessment of bio-accessible trace metal fractions in airborne particulate matter

“…To this solution, 3.2 g of pepsin were added, dissolved well and finally the volume was make up to 1 litre using bi-distilled water. Artificial lysosomal fluid and Gamble solution were prepared according to Colombo et al, 2008. Indium at level of 1 ppm was also added to the prepared leaching agents as an internal standard in order to overcome non-spectral interferences as well as errors related to manual sample handling steps.…”

Simulated Biological Fluids with Possible Application in Dissolution Testing

“…Citrate was used instead of proteins to avoid foaming and acetate instead of organic acids. Gamble's solution has a pH of 7.4, whereas ALF has a pH of 4.5 and has a much higher organic content than Gamble's solution (32).…”

Use of simulated epithelial lung fluid in assessing the human health risk of Pb in urban street dust

“…The development of specialised fluids to mimic other parts of the human respiratory system is also required, as particles in the lung can also be phagocytized, exposing the PM to lower pH environments. Indeed, a growing number of studies have observed higher Pb bioaccessibility following exposure to an artificial lysosomal fluid (ALF, pH 4.5-5.0) than observed for a more neutral Gamble's-type solution (pH 7.2-7.4) (Colombo et al, 2008;Potgieter-Vermaak et al, 2012;Zereini et al, 2012). Whilst inhaled particles would have to be phagocytized before significant exposure to a more acidic environment occurs, all PM will be exposed to the neutral lung fluid.…”