An Evaluation of the Environmental and Health Effects of Vehicle Exhaust Catalysts in the United Kingdom

Article excerpt

Since 1993, all new gasoline-engine automobiles in the United Kingdom have been supplied with three-way vehicle exhaust catalytic converters (VECs) containing platinum, palladium, and rhodium, to comply with European Commission Stage I limits on emissions of regulated pollutants: carbon monoxide, hydrocarbons, and oxides of nitrogen. We conducted a physical and economic evaluation of the environmental and health benefits from a reduction in emissions through this mandated environmental technology against the costs, with reference to urban areas in Great Britain. We made both an ex post assessment--based on available data to 1998--and an ex ante assessment--projected to 2005, the year when full penetration of VECs into the fleet is expected. Substantial health benefits in excess of the costs of VECs were indicated: By 1998 the estimated net societal health benefits were approximately 500 million [pounds sterling], and by 2005 they were estimated to rise to as much as 2 billion [pounds sterling]. We also found through environmental surveys that although lead in road dust has fallen by 50% in urban areas, platinum accumulations near roads have risen significantly, up to 90-fold higher than natural background levels. This rapid accumulation of platinum suggests further monitoring is warranted, although as yet there is no evidence of adverse health effects. Key words: air quality, economic evaluation, Great Britain, health risk assessment, pollution, pollution control, platinum, road transport, urban, vehicle exhaust catalysts.


In pursuit of efficient pollution control policies and the health benefits that flow from them, it can be useful to evaluate the costs and benefits of specific actions such as the mandated introduction of a technology like vehicle exhaust catalysts (VECs). Ex post evaluations allow realized benefits to be reviewed and the results to inform future policy decisions. Ex ante evaluations can also assist in the selection of appropriate policy interventions from competing alternatives. In this study we report on an evaluation of the short-term health benefits from the introduction of VECs to gasoline fueled vehicles in Great Britain. In addition to providing an evaluation of this particular technology, this paper illustrates the use of a relatively straightforward, low cost methodology that could be used more widely to address the evaluation of other, alternative technologies.

Road transport accounts for significant proportions of total United Kingdom emissions of oxides of nitrogen (N[O.sub.x]), carbon monoxide (CO), volatile organic compounds (VOCs), carbon dioxide (C[O.sub.2]), and particulate matter < 10 [micro]g in diameter ([PM.sub.10]), particularly N[O.sub.x] (52%), VOCs (37%), and CO (90%) (Quality of Urban Air Review Group 1993). Gasoline-fueled automobiles are the main source of road transport's contribution, accounting for some 50-90% of the sector's share of U.K. emissions (Holman 1996), and in urban areas the contribution from road transport is even higher. From 1993, to comply with European Commission (EC) Stage I limits on emissions of CO, VOCs, and N[O.sub.x], all new gasoline-engine automobiles in the United Kingdom have been supplied with three-way VECs (Salway et al. 1996). A catalyst increases the rate of a chemical reaction while itself not undergoing any permanent change (Heck and Farrauto 1995). VECs contain platinum, palladium, and rhodium, which catalyze the conversion of the incomplete products of gasoline combustion--N[O.sub.x], hydrocarbons, and CO--to [N.sub.2], [H.sub.2]O, and C[O.sub.2]. Automobile lead emissions have also been reduced effectively by the introduction of VECs because unleaded gasoline is required to avoid poisoning the catalysts. Surprisingly, although studies have addressed concerns over the release of platinum in particular (Helmers 1997; Rosner and Merget 2000; Zereini et al. 1998), there do not seem to have been any attempts specifically to assess the health benefits of the reduction in emissions from the introduction of VECs against their costs, either in Europe or the United States. …