Pyrrolizidine Alkaloids, Comfrey, and the Boraginaceae Family

I have been catching up on the debate about the limited evidence for 'dynamic accumulation' of key nutrients in plants such as comfrey (calcium: https://earthundaunted.com/which-dynamic-accumulator-plants-are-actually-helpful-for-your-garden-according-to-science/).  

I'd also already decided not to ingest comfrey myself due to the  pyrrolizidine alkaloid content (see below).

But today I learned that pyrrolizidine alkaloids can persist in the soil, both from the breakdown of e.g. comfrey aqueous extract ('tea') and dying plants, but also from root exudates.

Moreover, these persisting pyrrolizidine alkaloids can then be taken up into other plants - including our edible crops - from the soil.

Pyrrolizidine Alkaloids, Comfrey, and the Boraginaceae Family
By the Seed SistAs is a good discussion of the health hazards of pyrrolizidine alkaloids, with a couple of peer-reviewed sources.

https://seedsistas.co.uk/2025/06/30/pyrrolizidine-alkaloids-and-comfrey/

There is some very new peer-reviewed evidence about the conditions under which significant movement of pyrrolizidine alkaloids between soil, ground water and our edible crops can take place:

Fate of Pyrrolizidine Alkaloids in Soil: Insights from Myosotis arvensis L. and Senecio vulgaris L.
Toxins 2025, 17(7), 335; https://doi.org/10.3390/toxins17070335
https://www.mdpi.com/2072-6651/17/7/335

My initial take-aways from this are:
(1) I'm going to stop tolerating ragwort as a volunteer in my crop beds;
(2) As pyrrolizidine alkaloids accumulate in us, too, I'm going to work harder at diversifying my edible green manure options.

I'm hoping to find out significantly more about pyrrolizidine alkaloids in our edible crops in permaculture systems now .. what do we know?

I would still love to know more ..

I didn't see anything in the summaries about crop uptake of the alkaloids - just that it was present in the soil...and more research required.

I think that given a good biodiverse soil biota it wouldn't be something to worry about too much.

More research needed, but PAs have been detected in maize crops (mostly the leaves) for example, according to Nakurte et al. & references therein.  They consider groundwater contamination to be the bigger risk, I think.

"These findings underscore that soil properties—such as pH, organic carbon content, and cation exchange capacity (CEC)—are key determinants of PA fate, and the reversibility of sorption amplifies environmental risks by facilitating plant uptake and groundwater contamination."