On Saturday, September 19, 2015 at 11:46:21 PM UTC-4, . wrote:


Any claim that hobbyists, racers, lack of or incompetent
maintenance or what have you, constituted a noticeable effect
on air quality in general suggests a misreading of the problem.


It's especially silly given that people in those groups, that are
that determined, can surely undo what they did to get the car through
a test every two years. And like you say, they are such a tiny
fraction of the cars out there, it's like worrying about a fart in
a hurricane.