The stated reason for replacing rice protein with soy in their 2.0 formula was texture/mouthfeel, but I bet it has something to do with this as well. Why does

The stated reason for replacing rice protein with soy in their 2.0 formula was texture/mouthfeel, but I bet it has something to do with this as well. Why does rice tend to have such high heavy metal content? Is it simply coincidence w/ where rice tends to be grown?