Platinum and rhodium concentrations in airborne particulate matter in Germany from 1988 to 1998

Increases in platinum group element (PGE) concentrations in ambient air and dust since the introduction of automotive catalytic converters in 1988 is a cause of concern. Until now, data derived from engine-test bench experime nts have provided the basis for the assessment of human health risks associ ated with PGE exposure. Such experiments have provided valuable information regarding emission data that has been used to estimate ambient exposure co ncentrations. However, these data are not necessarily representative of typ ical environmental PGE exposure levels and conditions. Data on measured env ironmental concentrations is needed to provide a more adequate basis for th e assessment of exposure and related risks. Twenty air and airborne-dust sa mples were provided by the Umweltbundesamt (Federal Environmental Agency, G ermany) in the years 1988, 1989, 1992, 1997, and 1998. The samples were col lected in FranMurt/Main and the adjacent city of Offenbach. Far this, 11 to 80 m(3) of air were filtered over a 24-72 h period using a vacuum. Glass-f iber filters were used to collect samples. Sample platinum and rhodium conc entrations were determined rising adsorptive voltammetry Although the numbe r of samples collected in different years is limited, the results indicate a trend toward continuous increases in ambient concentrations of these meta ls between 1988 and 1998. Specifically, there were 46- and 27-fold increase s in Pt end Rh concentrations, respectively. Despite these observed increas es, the Pt concentrations measured (i.e., 147 pg/m(3) on average, with a ma ximum of 246 pg/m(3) in 1998) fell far below 15000 pg/m(3), which has been suggested as a guidance value (i.e., exposure at this level would be expect ed to be without appreciable health risk). The results of a particle-size d istribution analysis of one sample (8-step impactor) that was collected 150 m away from a street show that approximately 75% of Pt and 95% of Rh occur s in association with large particulate matter of > 2 mum, with concentrati ons reaching a maximum in particles of 4.7 to 5.8 mum. The remaining 25% of Pt and 5% of Rh is present in fine particulate matter of <2 mum. An approx imate 10% of Pt and < 38% of Rh in airborne particles was found to be solub le in 0.1 molar HCl. Further, the results indicate that most of the emitted PGE particles from automotive catalytic converters, particularly those bou nd to fine particulate matter, are capable of being airborne. As a result, PGEs are not only present in areas close to emissions (e.g., roads), but ca n be transported over longer distances.