Simply a single "pollution" wont address the subject correctly. Air pollution should lead to smog -> acid rain -> water pollution -> ground pollution. "Pollution" Broadly should would mostly impact biological entities. Pollution should not be singularly to encourage tier progression. In fact properly laid out, it can encourage both progression, machine selection, and ecological awareness. Progression of energy generation may be driven by reducing air pollution, while higher tier production machines should make more of it. Lending to ecological thoughtful building, including cleaning the pollution up properly before it makes it into the ecosystem
I would note that higher tiers don't really create more pollution per say. All machines of the class should create the same amount of pollution per operation, but higher tier machines process materials faster so they can create more pollution per minute than a lower tier machine.