heavy metals that are bound in the Earth are freed during mining. There are many heavy metals that are directly toxic to most life a.k.a. poisonous. In addition

heavy metals that are bound in the Earth are freed during mining. There are many heavy metals that are directly toxic to most life a.k.a. poisonous. In addition, some heavy metals bioaccumulate in the food chain -- that is, when a fish eats the plant with the metals on it, the fish does not excrete the elements, over time, then a predator eats many fish. It is a serious and well-studied effect.