3941
The use of catalytic converters , mandated in the US for 1975 and newer model-year cars to meet tighter emissions regulations , started a gradual phase-out of leaded gasoline in the US .
 location: US; location: US
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 location: US; location: US