I am a big lover of the plant comfrey in particular Symphytum Uplandica X.
I use the leaves of this plant internally as a water based preparation 30g dried leaves steeped in 1 litre of water for 4 hours and consuming 4 cups a week. I know people who have done this for 25 + years without issues.

However the FDA has stated that it should be banned because of the pyrrolizidine alkaloids that it contains.

I was just wondering where can I find the full report on how this study was conducted such as what species of comfrey was used, what parts of the plant were examined, leaves, roots, stalks or was it simply the whole plant.

What comfrey preparation did they test, alcohol based preparations, water based, infused oil based, etc.

A comparison chart or table showing the levels of pyrrolizidine alkaloids and other harmful toxins that are in the various specifies leaves and their roots.

Do the roots contain more toxins than the leaves, is one specified high in these pyrrolizidine alkaloids and the other species extremely low, etc.

I want a thorough report on these studies rather than simply reading "comfrey should be banned according to the FDA due to the high levels of pyrrolizidine alkaloids it contains. That studies showed in rats that consuming comfrey orally causes severe live damage... "