The Clean Air Act of 1970 required all cars after the year 1975 to be equipped with a catalytic converter. This act required all vehicles to cut their emissions by 90% in only five years. Later amendments to this act in the 1990s banned leaded gasoline sales by 1995, amplifying the need for catalytic converters by automobile manufacturers.
The first iteration of the catalytic converter contained steel beads attached to a mesh at both ends of the converter. These beads, coated in a catalyst, would create the transformation when the toxic gases came into contact with them. However, this method was later proven inefficient due to the beads shifting and wearing down over time. This inspired the more efficient honeycomb method on account of its high surface area. Dr. Carl D. Keith later invented a three-way converter. This was a more streamlined model that performs the original function of a catalytic converter while also transforming nitrogen oxides into nitrogen and water. Modern three-way converters can catalyze up to 98% of the toxic gases released from automobiles.