The specific cited quote may be a myth, but I'm pretty certain I'd first encountered the concept in the 1980s, most likely reading through Garrett Hardin's essa

The specific cited quote may be a myth, but I'm pretty certain I'd first encountered the concept in the 1980s, most likely reading through Garrett Hardin's essays (of "Tragedy of the Commons" fame, and some subsequent notoriety). Hardin does quote a contemporaneous (late 19th / early 20th century) source, and specifically the word "mud", which was, much as "fog", a euphemism. As "London Fog" actually described London smog in many instances, mud referred to excrement, largely (though not entirely) of equine origin. And yes, the idea was developed that continued urban growth would hit limits based on quartering, feeding, and mucking out huge horse populations which were required for local transport. It was electric omnibuses, cable cars, and trolleys which first provided a local alternative point-to-point-ish transportation network. Eventually autonomously-powered vehicles (automobiles) addressed the problem. It's worth noting that the situation wasn't purely solved. We outsourced one problem (animal-based drayage with concomitant feed and waste issues) with another (fossil-fuel based transport, with its own sourcing and effluent characteristics). Already by the mid-1800s it had been recognised that fossil fuels (coal, in particular) were a finite resource, and the first intimations of the global consequences of their use at scale (global warming) were coming into focus. Laughing or sneering at the concern, regardless of the merits of any given citation or reference shows a distinct lack of greater awareness.