Concentrations of Platinum Group Elements (PGE) (Pt, Rh, Pd and Ir) in the atmosphere of urban areas are increasing as a result of their release from the automotive catalytic converters and their adsorption in the particulate material. The PGE’s catalytic activity is therefore extended outside the vehicle systems.

The team analysed air particulate samples collected from two busy sites in Rome over the winter of 2004-2005. Using mass spectrometry to determine the chemical constituents of the samples, they confirmed that vehicle exhaust, as opposed to hospital incinerators and industrial sites, are the main source of platinum and related metals in the urban environment.

The researchers also confirmed the findings of an earlier study that suggests that platinum is present in vehicular pollution at four times the level of rhodium. The environmental evaluation of iridium used in catalytic converters provides the first benchmark for this pollutant as no detailed tests have been carried out previously.

In terms of public health, the researchers then looked at the way the platinum group metals interact with the natural antioxidant, vitamin C (ascorbic acid) and with a compound occurring in every human cell as a product of metabolic processes, the reduced form of nicotinamide adenine dinucleotide (NADH). They hoped to determine whether the metals from catalytic converters that have entered the atmosphere and been adsorbed on pollutant particles which can be breathed in could ultimately have a detrimental effect on health.

They used an electrochemical method to investigate how the platinum group metals from their particulate samples reacted with ascorbic acid and NADH. Preliminary findings from in vitro testing suggests that these metals can trigger deleterious reactions that decrease the amount of these molecules. Further investigation is required to determine the body’s response.

The researchers suggest that the emerging problem of platinum metal pollution must be considered in evaluating the benefits of vehicle catalytic converters. The researchers also suggest that closer monitoring of increasing levels of catalytic metals in urban pollution is a matter of urgency. Epidemiological studies of the health effects on children of these metals are under way elsewhere with metal content in urine samples providing a straightforward method of monitoring exposure levels.

Resources:

• “Automotive catalytic converters and environmental pollution: role of the platinum group elements in the redox reactions and free radicals production”; Claudio Botrè, Marina Tosi, Franco Mazzei, Beatrice Bocca, Francesco Petrucci, Alessandro Alimonti; International Journal of Environment and Health 2007 - Vol. 1, No.1,  pp. 142 - 152 DOI: 10.1504/IJENVH.2007.012229