[lum1n0l]

I'm currently learning about EDTA and its use as a chelating agent to clean boilers. I recently found out about EDTA's different salts and the fact that EDTA alone is a water insoluble compound. What I would like to know are several things regarding EDTA and its salts
1) does the fact that EDTA is insoluble make it hard/impossible for it to act as a chelating agent?
2) can these salts be formed by combining EDTA with the other chemicals involved? for example, can 4 parts of ammonia combine with EDTA to form tetrammonium EDTA, and, can elemental sodium, or sodium in any other form combine with EDTA to form tetrasodium or disodium EDTA? additionally, can something like tetrasodium EDTA be converted into tetrammonium EDTA when ammonia is added to tetrasodium EDTA?
3) what exactly makes EDTA a harmful chemical if it is water insoluble, and why is it considered a pollutant?

[Borek]

EDTA is insoluble

It has a very low solubility, but is definitely soluble.

Plus, it is acidic enough to dissociate and convert itself to salts (especially in slightly alkaline waters/soils), which have much higher solubility.

[Meter]

I do not have experienc with EDTA itself, but I have worked with DTPA (pentetic acid) and PDTA (1,3-diaminopropane-N,N,N',N'- tetraacetic acid) among other aminocarboxylate types ligands. Generally, they are not soluble at pH 7 but readily dissovle on addition of acid or base.

As Borek mentioned, soils are probably acidic or alkaline enough to cause dissociation and the EDTA will readily bind to any acceptor.

[rolnor]

Here you can read a little about EDTA, it forms different salts

https://en.wikipedia.org/wiki/Ethylenediaminetetraacetic_acid