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Platinum Group Element Pollution is a Growing Concern in Countries with Developing Economy Indra S. Sen* *
School of Earth, Ocean and Climate Sciences, Indian Institute of Technology, Bhubaneswar, Odisha 751013, India as China, India, Brazil, Indonesia, Malaysia, and Thailand. These Asian countries have experienced a phenomenal increase in vehicle sales amidst global economic slowdown (Figure 1). It is
Figure 1. Growth rate of the numbers of passenger cars sold in the world from 2005 onward.3 Europe, North America, and Australia witnessed a decline in vehicle sales during the most recent global economic slowdown, while Africa, Central, and South America, and in particular Asia have witnessed a steady increase.
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nthropogenic displacements of platinum group elements (PGE: osmium, iridium, rhodium, ruthenium, palladium, platinum) on the Earth’s surface are many orders of magnitude higher than those derived from non-anthropogenic (i.e., natural) sources.1 PGE Data on environmental samples suggest that high anthropogenic PGE concentrations are not limited to large cities with industrial centers and substantial construction activities, but contamination can be found in rural and remote locations. Anthropogenic PGE signatures have been found almost everywherefrom airborne particulate matters, to the snow over Antarctica and ocean surface waters, river, rainwater, industrial waste, and agricultural land. The major source of anthropogenic PGE is attributed to the use of catalytic converters in automobiles.2 Such converters are located in the automotive exhaust systems and are mainly composed of platinum, palladium, and rhodium. Their function is to transform emissions of NOx, CO, and unburned or partially burned hydrocarbons into more benign forms. However, thermal and mechanical attrition of catalytic converters is releasing PGE particles into the environment. Elevated levels of PGE are of serious concern because they can be hazardous to human health and cause chronic and subclinical diseases. PGE in ≤2.5 μm sized atmospheric particulate matter (PM2.5) have been attributed to increases in morbidity and mortality. Therefore PGE pollution is a global concern. There is a significant body of published information on environmental PGE contamination for America and Europe, with relatively few studies in countries with growing economies such © 2013 American Chemical Society
estimated that the automobile industry in China and India have grown at the spectacular rate of an average of greater than 15% over the past few years, and last year alone 30% of world passenger car sales were from China and India.3 Because of such an increase in the number of vehicles, a similar increase in the number of catalytic converters and accompanying PGE pollution is to be expected. It is also important to mention the potential role of two-and three wheelers (motorcycles) that use similar exhaust catalyst technology to reduce toxic emissions.4 Asia accounts for almost 85% of the new motorcycle sales with China and India as the world’s two leading two-wheeler manufacturers. In fact, the number of motorcycles in countries such as China, India, Indonesia, Thailand, and Malaysia can be an order of magnitude higher than automobiles.5 EURO 2 emission norms requires the use of catalytic converters in motorcycles. Currently, Asian countries are implementing catalyst technology to control motorcycle emissions.4 Since it is significantly cheaper to purchase, maintain, and operate motorcycles in crowded cities, a phenomenal increase in motorcycle sales is to be expected over the next decade. Received: Revised: Accepted: Published: 13903
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dx.doi.org/10.1021/es404890e | Environ. Sci. Technol. 2013, 47, 13903−13904
Environmental Science & Technology
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In summary, anthropogenic PGE contamination from automobile, two and three wheelers can therefore be substantial in countries with a growing automobile industry. As more than two billion people reside in India and China alone, it is desirable to evaluate and closely monitor the environmental PGE levels in Asia, and to quantify how they impact global PGE contamination levels. Unfortunately, PGE data on Asian soils, plants, water samples, and airborne particles are very limited. In particular, there is a large void in PGE data on environmental samples from the Indian subcontinent and South East Asia. Therefore quantifying PGE contamination levels in soils, plants, aerosols, and water samples at this part of the world is necessary, complemented by research designed to evaluate and understand PGE toxicity, PGE bioavailability, and its affects on human health. Finally, research should be undertaken that would move toward non-PGE based technology to reduce toxicity of automobile emission.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Sen, I. S.; Peucker-Ehrenbrink, B. Anthropogenic disturbance of element cycles at the Earth’s surface. Environ. Sci. Technol. 2012, 46 (16), 8601−8609. (2) Rauch, S.; Hemond, H. F.; Barbante, C.; Owari, M.; Morrison, G. M.; Peucker-Ehrenbrink, B.; Wass, U. Importance of automobile exhaust catalyst emissions for the deposition of platinum, palladium, and rhodium in the northern hemisphere. Environ. Sci. Technol. 2005, 39 (21), 8156−8162. (3) Sales Statistics for Passenger Cars; International Organization of Motor Vehicle Manufacturers (Organisation Internationale des Constructeurs d’Automobil − OICA); http://oica.net/wp-content/ uploads/pc_sales_2005-2012.pdf. (4) Emission Control of Two- and Three-Wheel Vehicles: Manufacturers of Emission Controls Association (MECA), Washington, DC, August 2008; www.meca.org/galleries/files/motorcycle.pdf. (5) Society of Indian Automobile Manufacturer (SIAM), Industry Statistics; http://www.siamindia.com/scripts/production-trend.aspx.
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dx.doi.org/10.1021/es404890e | Environ. Sci. Technol. 2013, 47, 13903−13904
