Question

A reason that many city workers lived in unhealthy conditions was

there was no garbage collection or sewage service.
people from rural areas introduced new diseases.
landlords were not allowed to improve their buildings.
people often did not clean up after themselves.

Answer 1

there was no garbage collection or sewage service.

Without proper sanitation, overcrowded tenements became filthy and disease spread quickly, creating unhealthy living conditions for city workers.