The main reason is the population increase, compounded by increased consumption by the population, the latter, the poor city planning exacerbates pollution.
The economic character predominates over the regional planning, and therefore, the spatial distribution of resources within the region is the main objective of regional planning, to achieve the economic, social and environmental goals.
The main reason is the population increase, compounded by increased consumption by the population, the latter, the poor city planning exacerbates pollution.
I agree whith your idea that the main reason is the population increase, compounded by increased consumption by the population, but I think this is the old reason, now the cities suffered from other reason which caused the pollution.