PGM 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 some groups expressing concern for the levels of PGM that may be increasing 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 within 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 advancing catalytic converter technology which has resulted in smaller amounts of PGM to be lost during the operational life of the vehicle.
A severe limitation of available studies, both old and recent, is they aim to 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 what 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 within catalytic converters and within atmospheric particulate matter.
This multi-year research programme resulted in a number of scientific reports and publications within the peer-reviewed scientific literature.