An article in The Federalist:
contains a section based on a 2016 report
Innate Immunity and Asthma Risk in Amish and Hutterite Farm Children — New England Journal of Medicine
the gist of which the Federalist article summarizes in the following three paragraphs:
While the Amish get down and dirty with old-school barn-raisings and horse-drawn plows, the Hutterites live and work and produce an astounding number of babies in tech-savvy communes. They employ computer databases and industrial farming techniques. As a result, the Amish are grubbier, and Amish children are less allergy-prone.
The Amish homes tested in the study had nearly seven times more endotoxic bacteria than Hutterite homes. The researchers found allergens in the dust of 4 in 10 Amish homes, while only 1 in 10 Hutterite homes had comparable levels. Yet Amish kids were four times less likely to have asthma and six times less likely to have allergies.
Due to the remarkable genetic similarity of the two populations, the study’s findings indicate a hearty immune response to a pathogen-rich environment. This provides strong evidence that soft-palmed kids who don’t play in the dirt are more likely to become asthmatic Eloi. It also shows how different approaches to the Ordnung produced unforeseeable effects.
As far as I know, I have never come across any Amish, but I did see some Hutterites when visiting Canada in 1978. So I found this rather intriguing.
But I do not see any prospect of transferring this to an urban environment. The assaults on one’s immune system and general well-being would, I think, be much more varied and more severe. And back in the good ol’ bad ol’ days, cities were much worse for one’s health, and in Mediæval England they were always seeking immigration from the countryside in order to keep their populations up.
 The Eloi were effete surface-living beings in The Time Machine, who were preyed upon by the underground-living Morlocks.