Wages are usually much lower in rural areas (if there are even jobs available), so this still applies. And, as others have said, there’s plenty of pollution caused by farms and factories in rural areas. I grew up in a rural area, and still remember the seasonal smell of cow manure, and the river that was so polluted you could only eat 1 fish per month from it. I also got a check from a class action lawsuit because a waste disposal facility caught on fire and spewed toxic smoke all over a 50 mile radius. And a local factory got caught just dumping toxic waste in the ground.