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Dave Whittaker wrote...

I spoke 10 days ago to a toxicologist with the Canadian Food Inspection
Agency. She said that NTA was a known animal carcinogen. She surmised
that at the concentrations presented in our planted tanks (EDTA<10 ppm)
both the EDTA and the NTA might cause problems. Apparently EDTA
affects blood-clotting capacity in mammals, although she thought
that the large size of the EDTA molecule would preclude it from
traversing fish gills. She also offered the opinion that EDDHA might
be a better option as chelant since less was required to sequester
a given amount of iron, and in contrast to EDTA and DTPA, EDDHA
was unlikely to harbour NTA as a contaminant. That's it.

Don't forget those water changes and keep an eye on your hemophilic

G. Kadar said with respect to the above...

>This chemical is used to treat  both acute and chronic heavy metal
>(lead) poisoning in humans.  It is also used in "chelation" therapy
>which is officially sanctioned in the US but not in Canada.  In
>addition, it is the substance that chelates calcium when dentists
>are performing root canal treatments.

>EDTA is also used as a stabilizing agent in certain injections and
>eye-drop preparations.Take a look sometime at the ingredients of
>such prepared food items, as Mayonnaise, some salad dressings
>(probably ranch dressing) and a myriad of other things, that may
>surprise you. The stuff is all over the place.

I just checked the label on the mayonnaise jar and it contains
calcium disodium EDTA. I'm surprised.

>Given it's extensive use in "invasive" therapies for human beings,
>perhaps the information written about in a previous post is referring
>to extremely high levels of EDTA.  The amount of EDTA introduced
>into an aquarium via PMDD is almost insignificant.

She understood the levels to be those found in home aquaria. I
figure that an aquarium might accumulate 5 to 25 ppm as EDTA
due to PMDD dosing.

>Furthermore, it's use would be banned in hydroponic gardening if
>it would be a major carcinogen.  There would go all the greenhouse
>grown vegetables.

Maybe. NTA is the carcinogen, EDTA is not. I took from the
conversation that the problems that EDTA might cause would be
associated with biological processes.

>EDTA passes through the gill membranes of fish.  It also passes
>through the membranes of the kidney and is thus excreted in the urine.

She didn't know, but she thought that it probably wouldn't.

>Perhaps there was some confusion as to EDTA and NTA.
>Who was this 'unnamed' toxicologist?

No confusion. I'll send you her name. Not every civil servant who
offers a free opinion wants their name published online.

>Now please, I really hate having to dust off my old textbooks.

Since you're the one with the textbooks, by all means dust them off.
I was looking for information. In the discussion three weeks ago, 
Dave Huebert's was the only opinion offered.

And since I consume a lot of mayonnaise, your point is well taken.

Dave Whittaker
ac554 at FreeNet_Carleton.ca