If you declare too many things to a "human right" it removes wiggle room for good policy making. Also, the US already has stronger rules against vehicle pollution than the EU (in terms of pollution that directly damage health like NOx and PM). If it's going to become a "human right" then countries who propose it should be leading it in the first place.
One thing it does is to buttress the fictive sovereignty of all these hundreds of "nations" which are not actually sovereign or independent, but enjoy promoting the notion that they are out of the belief that it makes the citizens more spirited. If the people believe that the 'new boss' is the people, rather than the 'same boss as the old boss,' they're less likely to revolt or otherwise be demoralized. That's the theory, but it's one of those things where the people who are supposed to 'get the joke' no longer get the joke, so it leads to a lot of confusion and muddled thinking on the topic.
The moment that any "nation" asserts sovereignty independent of the 'international community,' the fiction is exposed. There are only a small number of countries actually capable of asserting sovereignty and the US is one of them, China's another.