Lead can enter water mainly through two primary mechanisms:
- It leaches into water as old pipes corrode.
- It is released into waterways with industrial waste.
While the first option is the most common way lead contaminates drinking water in urban areas (particularly in places with aging infrastructure), the second option is also a significant source of lead pollution, especially in industrial areas.
The other options are less relevant to the typical pathways through which lead enters water sources. Therefore, if I had to choose one point from your provided responses, the best answer would be:
It leaches into water as old pipes corrode.