IPA Position Paper on Clean Diesel Vehicles and Air Quality


The International Platinum Group Metals Association (IPA; www.ipa-news.com), based in Munich, includes among its members the manufacturers of 90% of the world's vehicle emissions catalysts (autocatalysts) and the producers and refiners of 70% of platinum group metals (PGMs). As a product group, autocatalysts are essential in controlling pollutants emitted from gasoline and diesel vehicle engines, thus improving air quality and protecting human health and the environment. PGMs are the active materials in autocatalysts and are essential to their performance.

Legislators at EU, national and local levels are concerned at current levels of air pollution in the European Community, particularly in cities. Following the latest developments, there have been calls to reduce the use of diesels and even to ban diesel vehicles from some city centres on account of levels of oxides of nitrogen (NOx) recorded in urban areas which exceed World Health Organisation (WHO) standards. However, according to the European Environment Agency (EEA), transport accounts for less than 20% of particulate emissions and for one third of NOx emissions, a figure which has been trending sharply downwards.

Diesels form a significant part of today's European vehicle fleet, accounting for 35% of cars already on the road and for over half of new cars sold. This market success largely reflects the fuel efficiency of diesels, which produce 15-20% less CO2 per kilometre than equivalent gasoline-powered vehicles. European legislation requires vehicle manufacturers to significantly reduce their fleet average CO2 emissions by 2021 and diesel vehicles are an important means to achieve this. Many European countries provide incentives for consumers to buy diesel cars by reduced duties on diesel fuel.

European vehicle emissions legislation has evolved steadily since the first Euro 1 standards were introduced in 1993, supported by innovations in combustion and emission control technologies and cleaner fuels. NOx limits for diesel engines over the last 15 years have been reduced by 84%, and particulate limits by 90%.

Modern clean diesel vehicles, compliant with the latest (Euro 6) generation of EU emissions legislation, use highly efficient filters to remove over 99% of fine particles from diesel exhaust and carry advanced autocatalysts to control NOx emissions. Euro 6 rules also address the criticism that vehicles meeting the previous Euro 5 legislation have failed to match laboratory test cycle conditions in actual road driving, by preparing for the introduction of real-world emissions verification testing of vehicles from 2017.

Producers of PGMs and manufacturers of autocatalysts and filters have an excellent track record of reliably supplying materials and investing in research into novel technologies which have enabled stricter emissions controls to be introduced, and, in partnership with vehicle manufacturers and the fuel industry, are working to make diesel vehicles even cleaner in the future.

IPA fully supports other measures to improve air quality, such as stricter testing and monitoring of emissions control performance under real driving conditions; measuring the long-term effectiveness of emissions controls; and accelerating the rate of renewal of the vehicle fleet.

IPA believes that the answer to pollution generated by diesel vehicles is not to restrict their use, but rather to incentivise fleet replacement of pre-Euro 6 diesels, especially in urban areas; to ensure that the currently emerging Euro 6c rules are successful in reducing real world emissions; and to encourage further emissions reduction technology development and legislation. This approach will retain the fuel efficiency benefits of diesel vehicles without adverse impacts on air quality.


  1. Vehicle emissions catalysts include exhaust system-related autocatalysts (substrates with incorporated or coated catalytic materials), catalysed particulate filters, and ancillaries such as emissions adsorbers. The latest generation of these products converts up to 99% of combustion engine exhaust pollutants (HC, CO, NOx and particulates), enabling vehicle manufacturers to met European Union regulations on air quality.
  2. Platinum, palladium and rhodium are the three PGMs used in autocatalysts. They are mainly produced in South Africa and Russia. Approximately 53% of annual demand for these metals is derived from the manufacture of autocatalysts.
  3. Untreated engine exhaust gases are harmful to human health. They may variously cause cardiovascular and lung diseases, impair heart and lung function, contribute to cancer and create photochemical smog and acid rain.
  4. Legislators have increasingly tightened vehicle exhaust pollution limits to prevent this, to the point where it would take 100 of today's cars fitted with autocatalysts to produce as many harmful emissions as just one car in the 1960s.
  5. New trucks and buses meeting the latest standard (called Euro VI for these heavier vehicles) have already been shown to deliver real-world emissions reductions. For instance, real-world tests of Euro VI buses in London have shown an effective 95% drop in NOx emissions compared to Euro V buses (Transport for London).
  6. Vehicles and transport are only one source of air pollution. Others include electricity generation, industry, households, mineral extraction, agriculture, waste treatment and natural sources such as volcanic activity and windblown dust. Over 80% of particle emissions (PM10) derive from economic sectors other than transport, such as the commercial and household sectors (European Environment Agency, 2012).
  7. A study in 2012 by the International Agency for Research on Cancer (IARC) concluded that diesel exhaust is carcinogenic to humans. It should be noted that the IARC study focused on out-dated diesel engines using inferior quality diesel fuel. Modern clean diesel technologies found on Euro 6 certified vehicles, already utilising higher purity fuel, high-efficiency autocatalysts and diesel particulate filters and improved engine controls, present a very different picture. Indeed, IARC has acknowledged that new technology diesel exhaust is likely to give very different results.