Some of the vehicles, especially chicken buses and trucks, but no where near all of them, belch black smoke in great amount here in Guatemala, especially when starting up hills, of which their are endless.
I dont' think there is any required pollution inspecition, and it makes me think that the demands, largely from the US I think, for cars with pollution controls, have benefitted Guat. and other countries too, because the controls work well until they break, and only a few break.
It all depends on where they import their trucks from. Even then, if either there aren't any pollution control laws, or no effective enforcement, the pollution controls may be disabled in country to improve mileage. I can imagine that in a poor country without pollution enforcement owners may make money by removing and selling the catalytic converters from vehicles that have them and welding in a plain piece of exhaust tubing to close the gap.
There is no require pollution inspection here, either.
I remember working in Venezuela. After oil put tons of money into the economy, the peasants were buying used American cars, old crap that got shipped there. And the gasoline was made from high-sulphur crude that they couldn't export. So the air pollution was terrible.
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