Environmental and biological monitoring of iridium in the city of Rome Ivo Iavicoli a , Giovanni Carelli a , Beatrice Bocca b , Stefano Caimi b , Luca Fontana a, * , Alessandro Alimonti b a Institute of Occupational Medicine, Universita ` Cattolica del Sacro Cuore, Largo Francesco Vito 1, 00168 Rome, Italy b Environment and Primary Prevention Department, Istituto Superiore della Sanita ` , Viale Regina Elena 299, 00161 Rome, Italy Received 5 June 2007; received in revised form 19 September 2007; accepted 21 September 2007 Available online 5 November 2007 Abstract 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 environ- mental 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), PM 10 and PM 2.5 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 PM 10 and PM 2.5 fractions were 1.43 ± 1.66, 0.44 ± 0.27 and 0.36 ± 0.19 pg m À3 , 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. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Workers; Tram; Urine; Particulate matter 1. Introduction Iridium (Ir) is a noble and precious metal belonging to the platinum group elements (PGEs) together with palla- dium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru) and osmium (Os). In nature, metal Ir is found in alluvium deposits associated with Pt and other metals of the PGE group. It is also a by-product of the nickel mining industry. In industrial applications, Ir is used with Pt as a hardening agent in alloys, therefore it is principally used in metallurgy devices and electrical contacts. Other technical uses derive from its ability to form alloys with Os (Lide, 2005). Iridium is the most recent PGE to be introduced into the motor industry. In fact, it has been used for the implemen- tation of new-generation ‘‘DeNO x ’’ catalytic converters which have been developed to further reduce the emission of nitrogen oxides in the exhaust of lean-burn engines (Merget and Rosner, 2001; Ravindra et al., 2004). Although such devices are important for improving air quality by considerably reducing hydrocarbon, carbon and nitrogen oxide levels, they nevertheless cause an aerosol containing Ir and other PGEs, to be introduced into the various compartments of the environment. Thus, the increasing use of Ir in the motor industry could result in a higher exposure by inhalation not only for the general population (Botre ` et al., 2007) but also for work categories exposed to vehicle traffic. The toxicokinetics of Ir has been assessed through experimental studies performed on animal models, mostly on rats (AECD, 1951a, 1951b). When metallic-Ir aqueous aerosols were inhaled, metal was deposited in the upper 0045-6535/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2007.09.037 * Corresponding author. Tel.: +39 06 3055329; fax: +39 06 3053612. E-mail address: lucafontanamd@gmail.com (L. Fontana). www.elsevier.com/locate/chemosphere Available online at www.sciencedirect.com Chemosphere 71 (2008) 568–573