Who should pay for cleaner air: polluters, taxpayers or the people who benefit?

Cleaner air costs money. Filters, cleaner fuels, new buses and stricter inspections all have a bill. The same is true for broader climate policy: someone pays, whether through a carbon price, a tax, a higher product price or a public subsidy.

There are at least three principles people reach for. The polluter should pay, because they created the harm. The public should pay, because clean air is a shared good. The beneficiaries should pay, because they gain most. Each has a fairness argument and an effectiveness argument, and they often point in different directions.

We are asking for an answer that does more than pick a side. A good answer would say which principle it favours and why, who ends up bearing the cost in practice, what happens to low-income households, and how the approach could be checked after it is introduced.

Real examples from your own city or country are especially welcome.