I am no chemist, but the way I understand it, catalytic converters, and unleaded gasoline, reduced pollutants that were getting into our water supply at an alarming rate before 1974.
The purpose of the catalytic converter is to reduce carbon monoxide and unburned hydrocarbons. Nothing can eliminate them completely except shutting off the car. I know this because my oxygen sensors tell me so.
So if you want to kill yourself quickly, use a pre-1974 car. A new car will still kill you, but it might take a couple minutes longer. In either case, you’ll be asleep before you kick the bucket, so it doesn’t really matter.