Amajor cause of pollution in medieval cities was

Unclean way of life

Explanation:

People in the Middle Ages didn't care much about hygiene. The streets were filthy, you could see different animals wandering on the streets, and the rats were spreading diseases across the cities.

This is why in the Middle Ages more people died out of sickness than out of some other cause.

i think its the outcome of people's preferences.

i belive the classic sword and a shield would do