I've been thinking for a while that there are so many possible sources of poisons it's very hard to monitor them all. But there is only one of me. So logically I should check if I have elevated levels of poisons. Then, and only then does it make sense to start monitoring my surroundings to trace where it came from.
There are no hand held devices which will tell you if the soil you're vaguely near has heavy metals in it, nor how much.