From a sustainability perspective, what is a method by which a city can set priorities regarding pollution. In other words, which pollutants are the most important to reduce. So many pollutants are in the air, water and ground, it is difficult to know what to do first. Thanks for any examples from other cities.
You ask a very open ended question. You could refine it somewhat by stating what you see as the pollutants and their problems.
Decide on what your priorities are, and how you will make tradeoffs between them.
Is global warming more important that local health? Is local health more important that a clean river?
One way is to decide on the externalized cost of each pollutant. This is tough. Search the literture for the externalized cost of Carbon dioxide. You have to take into account the cost of displaced people, extinction, loss of habitat. Various estimates have averaged about $40/ton, but the standard deviation was $80, so the range is pretty wild.
One way is to put an imaginary bubble over your city. Everything you put out there is going to stay there. Indefinately. This limits the scope of calculating external costs, and will distort the results (air pollution becomes relatively more important)
When devising policy consider how it will be enforced? Unenforcable laws are bad.
Where you can do so, encourage the right behaviour/discourage the wrong behaviour with a tax rather than a rule. Taxes make money. Rules cost money. So for example: Make the registration fee for all electric vehicles zero. One city has free parking at all city meters for all electric vehicles.
When you start a tax, add it slowly so that people can figure out how to do things better. E.g. If you want to decrease smog, and you think that it is primarily caused by motor vehicles, than put a 25 cent a gallon tax on gasoline, and tell everyone that it will be going up 25 cents a year. Get the municipalities around you on side. A gas tax is hard to enforce if you can fill up outside city limits. (If the won't cooperated, tax entering the city, on the basis that you are driving there with untaxed gas.) Anyone with out of state plates gets in free.)
Go after the low hanging fruit. Things that are bad your health, bad for your river, bad for your fishery and bad for tourism get priority over ones that only endanger the Lesser Frog Newt
Go after the ones that are easy to enforce.
Generate revenue by taxing excess. E.g. vehicle registration is proportional to the square of the vehicle weight. A F250 pickup (at 5000 lbs) costs 25 times as much to register as a Smart Car (at 1000 lbs) The first can of garbage each week is $5. The second one is $10. The third one is $20
Examine other cities to see if they have policies that can help. E.g. Vancouver supports Go Cars -- a car share company where you can rent a car as needed. Edmonton has the most efficient garbage recycling program in the world.
Change your zoning laws.
Require any major industry to create housing for at least half it's work force on the same plot of land.
Requiring people to live near the factory will put pressure on the factory to be quiet and tidy. B: Many of them can walk to work.
Allow small business to take over residential blocks. Perhaps zone one block in 6 as a business block.
Encourage multiple use buildings where the bottom floor is shops, the next floor professional use, next floor residences, top floor park.
If you want a more specific set of recommendations, be more specific in your question.