Fungi also do this.

https://usfblogs.usfca.edu/sustainability/2022/02/03/mycorem...

Even if true, that would only clean the top few inches of soil (whatever depth the roots go), right?

Normal toxic site cleanups that I have read about usually involve at minimum replacing topsoil to a depth of several feet.

Not to challenge your perspective because I agree to some degree, but hemp roots grow >=3,<=6 feet down due to the tap root.

What do you do with the hemp once it has absorbed the toxins?

Dump it either on a toxic waste landfill or at a high temperature incineration site [1].

[1] https://www.novus-environmental.co.uk/blog/why-is-hazardous-...

Use cannabis plans to extract the pollution from the soil, then extract and concentrate the pollution from the biomass, then find a way to safely store it or break it down safely.

It depends. Some plants will break certain elements down into less toxic components. In the best case, the components are non-toxic and you can do whatever you want with it.

Nothing can breakdown lead and other toxic metals unless you have a neutron source.

I usually turn my old lead into gold. I've almost perfected the technique.

Blaze it

No! a) these aren't the THC types so you won't get high and b) the hemp is a collector, so the nasty stuff would be in the tree.

This material is for industrial hemp, making rope and fabric and things.