During the industrial revolution there was a spectacular increase in population, mainly due to the fall in the death rate caused by the improvement of hygienic, sanitary and food conditions that was largely reflected in the reduction of infant mortality. In this period, the first vaccinations are born and the sewage and wastewater treatment systems are improved. A more abundant and regular diet, not subject to fluctuations in crops, lowered the incidence of epidemics and made possible the almost complete disappearance of catastrophic mortality, especially infant mortality.
These scientific advances, added to the new job opportunities offered by the big cities, produced an unprecedented movement of people. These people from the countryside moved en masse to the big cities.
