I think a cool idea was to have CO2 as well as oxygen, meaning trees/tree farms could suck CO2 in and produce oxygen. Colonists would breathe in oxygen and produce CO2 so there would have to be a balance. Buildings would produce CO2 instead, basically pollution. Colonists would have to have oxygen as well, even at the start. I had an idea for an oxygen pump basically a dome with trees inside producing oxygen and taking in CO2. Pollution would cause some areas to be unlivable in maybe causes death/radiation poisoning but that would be with a lot of CO2. Trees could stop this from happening. Another Idea for it would be acid rain every so often if you had tons of CO2 wearing down buildings much quicker. This is my idea but I don't know if it's a good one or not. I think it would go well with Dolphin's trash Idea. This is my basic thoughts that could probably have some more ideas added to it, but I think it would go well with this new smog thing coming up. I think that it could add really well to the unhappiness of colonists and giving the game an extra flare. If colonists where near pollution maybe they could get depressed, maybe even committing suicide (Remember executions make people explode into chunks of flesh) It would have an official notification to tell you they were about to jump. If you had police maybe they could stop them or something. I'm trying to shape it to the update that is upcoming even though I know little about it I do know there is smog. I would recommend having some help/more ideas to add to it to clear out any weird things I come up with.