I teach economics and am (still) working on a project where I find Broadway songs that can teach economic concepts. I haven't yet found much on externalities/pollution, however.
Do you know any songs that discuss pollution I could use?
Thomas Dolby (who has written concept albums but never a full musical) contributed two pretty good songs to the pretty bad animated musical "FernGully." One, "Toxic Love" deals with pollution; the other, "Battyrap," deals with using animals to test cosmetics and medical procedures.
I too immediately thought of Tom Lehrer. If you are interested in non-broadway work -- 1960s stuff -- let me know. there are a whole cadre of those. But I wont go there unless you so say, since your post was for Broadway songs.
OK -- one -- What Have they Done to the Rain -- Joan Baez