A good example of government regulation improving quality of life!
Sounds good but it is totally impractical if you've had any experience with the legal system.
What if the cost of cleaning is smaller than the cost of changing business practices to protect health and the environment?
Or rather, how this sort of thing happens because of the ‘wrong sort of’ government action
The National Galleries near the Mound was cleaned entirely a few years back - it's actually starting to collect dark marks on it again.
(edit: come to think of it, entire central Edinburgh area still smelled of coal smoke in the mornings until about then, too, though Musselburgh even more so)