What an interesting subject you have breeched here Eric. I have noticed more and more people becoming fearful of this sort of thing. So, let me give a little information about this subject.
Just about every University has had at least one study done on the effects of soil contamination and produce content of those contaminants. There is so much data now that it can be confusing, and much is indecipherable by laymen.
Heavy metals: Top concern is Lead and Arsenic. These are found just about anywhere there is or has been a; house, factory, Filling station, building, road, etc. These contaminants are persistent and are indeed taken into the edible parts of vegetables, berries, all tree born fruits.
The levels of toxins found in all of the produce that has been ever tested is low, BUT toxins are accumulative in the human and all animal bodies. This means the more of the contaminated fruit you eat, the higher your toxin levels will be. This is of concern because they buildup inside your body, eventually they will reach harmful levels. (most likely years)
These two heavy metals are found in nature, and they can be found everywhere in nature. The grounds for concern are when we garden in areas that humans have increased the quantity of heavy metal toxins. In these places it is wisest to lay down a soil barrier and build
raised garden beds, this will reduce or eliminate the probability of contamination of food grown in that space.
There are many other "heavy metals" that contaminate soils but these two are at the top of every science list published because they predominate the populated areas.
So, what are we to do if all we have for garden space is
land that has high(er) concentrations of heavy metal contaminants?
We can excavate the "bad soil" and replace it.
We can block it with a barrier and then garden above that barrier in raised beds.
We can turn the area into a "remediation" space with copious numbers of
fungi, bacterium and flushing systems (sand pit into reed bed, into moss bed into mycelium rich
wood chip bed into holding
pond or garden bed.
The last option will take around one year to yield good results but, any
mushrooms that come up there (ever) will need to be destroyed and never used in
compost or anything else. (
trees with edible leaves (Moringa as example) fall into the never eat and destroy category )
This goes for any other item harvested from this area for a minimum time period of 5 years.
Even then the area would need to be tested for levels of contaminants prior to changing usage.
Is it Safe to eat the fruits, berries, vegetables grown in suspected contaminant containing soil? Yes, to a point, one must remember that toxins that will come from such soil are accumulative in the human body, and any other animal body or product (eggs for example) of the animal.
If you sample plants growing in heavy metal contaminated soil the levels of toxin quantity are highest in the root/ stem system, then leaves, then vegetable or fruit the plant produces. In the case of root vegetables, the produce will have a high concentration level.
In the case you described, the prudent method would be to "container plant the bushes and trees".
Hope that helps your decision making process.
Redhawk
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