Question

why does improving air quality have to be a world-wide effort

Answer 1

there are a number of operations and machinery, human activity, in general that lead to poor air quality or in other words pollution. therefore everyone would need to be aware that their actions causes air pollution. also we should bear in mind that air does not remain in one area all the time it spreads through diffusion thus affecting the whole planet. So what i am saying is basically one man cannot stop pollution it has to be a mutual effort of all nations.