Environmental and biological monitoring of iridium in the city of Rome

The use of iridium in the latest catalytic converters to further reduce nitrogen oxide emission in the exhaust of lean-burn engines could result in increased atmospheric levels of this element in high-density vehicle traffic areas. The objective of this study is to assess environmental Ir pollution and its urinary levels in workers and an urban control group. Environmental monitoring inside a tram consisted in air samplings of total suspended particles (TSP), PM10 and PM2.5 carried out during November 2005. Urinary Ir levels were evaluated in 64 municipal tram drivers and in 58 administrative employees as controls. Quantification of Ir in air samples and urine was performed by means of Sector Field Inductively Coupled Plasma Mass Spectrometry. Means ± standard deviation of Ir levels in TSP, in PM10 and PM2.5 fractions were 1.43 ± 1.66, 0.44 ± 0.27 and 0.36 ± 0.19 pg m-3, respectively. No statistically significant differences were observed among urinary Ir values in the exposed subjects and control group. The Ir levels in Rome air are still sufficiently low, even if the increased use of new Ir-based catalysts could be of some concern in the near future. The results of our study are of interest as they are a first attempt to explore airborne levels and urinary concentrations of Ir in an urban context at medium-high density of vehicle traffic. Particular attention should be given to the fact that Ir was found in the finest dust particles as the effects of fine particles containing Ir have not yet been studied.