- https://en.wikipedia.org/wiki/Zoning#Functional_zoning_-_cat...
- https://en.wikipedia.org/wiki/Zoning#Criticism_of_zoning_law...
Then that Wikipedia article needs to be amended.
Look at an example from the real world. This is happening right now, in Portland Oregon. http://www.portlandmercury.com/portland/two-portland-glass-c...
The problem is that glass factories are "adjacent to a 100-child daycare facility, two public schools (Cleveland High School and Winterhaven K-8), and a city park."
These factories have been emitting metals such as cadmium and arsenic into the air. As you can imagine, this being Portland, everyone is quite upset. And rightly so.
You can argue about the quantities of emission that any given plant should be allowed. But you can't argue that, for any given emission level, society as a whole is much better off if these factories aren't adjacent to daycare facilities and schools.
Keeping schools and factories separated is a very legitimate "safety" goal of zoning.