From Makers: The New Industrial Revolution:
Although we think of factories as the “dark satanic mills” of William Blake’s phrase, poisoning their workers and the land, the main effect of industrialization was to improve health. As people moved from rural communities to industrial towns, they moved from mud- walled cottages to brick buildings, which protected them from the damp and disease. Mass- produced cheap cotton clothing and good- quality soap allowed even the poorest families to have clean clothing and practice better hygiene, since cotton was easier to wash and dry than wool. Add to that the increased income that allowed a richer and more varied diet and the improved access to doctors, schools, and other shared resources that came with the migration to cities, whatever ill effects resulted from working in the factories was more than compensated for by the positive effects of living around them. (To be clear, working in factories was tough, with long hours and poor conditions. But the statistics suggest that working on farms was even worse.)
It’s interesting that the industrial revolution seems to have led to a net increase in health even at the beginning. I had always thought that people who worked in factories experienced much worse health overall. Given that the switch to agriculture did have a negative impact on health, it seems that social changes have pretty un-intuitive consequences.