Some soil pollution can occur naturally. In the course of soil formation some rocks containing undesirable amounts of particular elements will weather and breakdown and pass these elements on to the soil where they enter the domain of plant roots. Plants can take up these in abnormal quantities and while the plant may survive, animals foraging on them may become sick or die and humans can also be affected. There are many examples worldwide where either excessive amounts of particular elements in soil have created health problems in a particular region