So I've been getting into herbs recently, and this is the chemical that makes people concerned about comfrey, borage, coltsfoot, etc. My understanding of it is this: the scientific studies that show that these plants are dangerous have subjects consuming abnormally huge quantities of these plants (i.e. one study on comfrey was feeding lab rats comfrey as 50% of their diet, and they developed liver lesions). Under normal conditions both animals and people using these herbs as medicine would be consuming FAR less of the plant, and therefore far less of these compounds, which aren't dangerous in small quantities. While some of these plants' nectars do contain pyrrolizidine alkaloids, again, the amount would be so small that unless you ate (drank?) gallons and gallons of the honey, it wouldn't affect you in any negative way.
