PGMs in the environment

The addition of catalytic converters to automobiles has had immense success in reducing the levels of harmful pollutants emitted by cars and other vehicles with internal combustion engines. In use, tiny amounts of PGM within the autocatalyst become detached and are emitted with the exhaust gas into the environment. Although these amounts are extremely small, the high number of vehicles fitted with catalytic converters has resulted in concerns regarding increasing levels of PGM in the environment and whether this may pose a risk to the general public or the environment.

A number of research groups have published studies measuring levels of PGM – mostly platinum and palladium – within environmental media. Mostly this has been airborne particulate matter and roadside dust in urban environments experiencing high levels of traffic.

Many of the published studies are old and do not provide a reliable insight into present-day levels of PGM in the environment, which will be influenced by the greater number of years catalytic converters have been in common use, but also the advances in catalytic converter technology which have resulted in smaller amounts of PGM to be lost during the operational life of each vehicle.

A severe limitation of available studies, both old and recent, is that they measure only the total metal; there is no attempt to speciate the metals to determine what chemical form they are in – which is critical to understanding their properties and the risk they may pose.

In 2011, IPA sponsored an extensive programme of novel research at the University of Wisconsin in the USA, to better understand both the levels and speciation of platinum in catalytic converters and atmospheric particulate matter.

This multi-year research programme resulted in several scientific reports and publications in the peer-reviewed scientific literature. Summaries of the main project reports are linked below.