Why did automobile emission standards increase demand for platinum-group metals during the 1970s?

During the 1970s, the demand for platinum-group metals increased significantly due to the implementation of stricter automotive emission standards in the United States and other countries.1

To comply with these new regulations, automobile manufacturers began installing catalytic converters in vehicles to reduce the discharge of noxious gases. These devices utilize platinum, palladium, and rhodium as catalysts to promote the conversion of harmful exhaust components—specifically unburned hydrocarbons, carbon monoxide, and nitrogen oxides—into less harmful substances like water, carbon dioxide, and nitrogen. This technological shift, driven by the Environmental Protection Agency and similar global bodies, established the automotive industry as a primary consumer of these metals.23451