I don't believe that increased population necessarily means greater pollution. Consider the case of New Delhi. A decade ago when I visited New Delhi, the air was foul. But the air was, at least to the eye, much clearer at the beginning of 2005. Why the transformation? Many attribute the improvement to the local regulation requiring buses and taxis (including the ubiquitous 3-wheeler tuk-tuks) to switch their fuel to CNG (compressed natural gas). So a major apparent success.
But consider another development: the introduction of the aluminum drink can. Though many of my students may be too young to remember, the can was a nuisance not only because people would litter carelessly, but also because it had a zip tab that had to be pulled off and discarded separately from the original can. I believe that was banned some two decades ago, and now we no longer see the highways littered with tiny aluminum pieces that are difficult to clean. Today, Americans have a top that doesn't separate from the can itself.
One might have expected Coke and Pepsi to adopt the same measure throughout the world, imposing it on their bottlers. Yet, that is sadly not the case--the zip top can still exists in the 21st century in India.
Perhaps Coke might argue that it would make the can too expensive for average Indians, and that Indians are therefore better off with the more polluting container. But I'd like to see that issue made plain.