> Historically, more efficient agriculture meant a population boom.

But also a precipitous drop in life expectancy. Life in industrial towns in 1800s England was grim. Make of that what you will.

Pollution.

In the towns yes. A wealthy city man could expect to live fewer years than a labourer in the countryside.

Surely a factor, but hardly the sole explanation; malnutrition rose, that should give you some pause.

Pollution, malnutrition, maiming by industrial or mining equipment (huge percentage at the start).