That's the devs' job, not mine
But they can have a
Pollution level for each tile just like the
Appeal level
it can range from Extremely Clean to Clean to Average to Polluted to Terribly Polluted depending on the improvements built on the tile and nearby tiles (every tile starts in Ancient Era as Clean, woods +1, mine -1, factory -2, etc)
They can add an Environment/Pollution Map Lens (similar to Settler/Tourism Map Lens, Green = clean, Red = polluted) so players can keep track of their environment
if a tile remained "Terribly Polluted" for a few turns, it changes the features on the tile, lowers Appeal, scares Tourists away, cities on polluted rivers lose the "clean water" bonus, resources like Cattle and Fish can disappear...
And it can spread to nearby tiles and spread deadly diseases, lowering your population/citizens. It will force players to balance between growth and keeping the environment clean.
Policies can reduce/increase Pollution too, like encouraging citizens to use bicycles instead of cars, spend big on solar energy and ban Coal mining, etc.
On global scale, Pollution adds to Global Warming, causing sea level to rise, destroying coastal tiles or/and Natural Wonders, increasing the chance of natural disasters, forcing players to push their environment agendas in United Nations to reduce Pollution (or nuke the countries refusing to reduce pollution)
Speaking of resources, I fail to understand why the people in my civilization can't bring Wheat from this Plain tile to plant on the nearby Plain tile, or bring Cattles from 1 grassland tile to another