I recall a discussion during the 2-year program about PA's from Comfrey, Borage, etc. leeching into the soil and being transferred to honey via bees. I was wondering if you happened to have links to any studies related to this on hand? I checked the "Additional Resources" section of the Comfrey sheet but didn't find what I was looking for. I'm a community gardener and this topic keeps coming up for me because people want to make Comfrey compost tea. What I recall from the discussion was that the PA's were showing up in non-PA producing plants that were grown in the same soil, or near soil where PA-producing plants had grown. I think there was also a mention of a big honey recall in Europe, or maybe mass testing of honey, due to high levels of PAs. I'd be interested to read more into this subject. Thank you!

Food Chem. 2016 Dec 15;213:163-168. doi: 10.1016/j.foodchem.2016.06.069. Epub 2016 Jun 22. Interspecific transfer of pyrrolizidine alkaloids: An unconsidered source of contaminations of phytopharmaceuticals and plant derived commodities Melanie Nowak 1, Carina Wittke 2, Ines Lederer 3, Bernhard Klier 4, Maik Kleinwächter 5, Dirk Selmar 6 Transfer of pyrrolizidine alkaloids between living plants: A disregarded source of contaminations February 2019 DOI: 10.1016/j.envpol.2019.02.026 Lab: Dirk Selmar's Lab