Contamination of Norwegian honey by pyrrolizidine alkaloids from plants and the active ingredient clopyralid in herbicides

Honey can be contaminated by various natural and anthropogenic substances, posing a health risk to consumers. Pyrrolizidine alkaloids (PAs) are naturally toxic compounds many plant species produce to protect against herbivores. Honey may become contaminated if bees collect nectar and pollen from PA-producing plants. Clopyralid is the active ingredient in some herbicides, including Matrigon 72 SG, approved for weed control in oilseed rape in several countries. As a systemic substance, its application before flowering may contaminate nectar, pollen, and honey. In 2023, 30 Norwegian honey samples were tested for the content of PAs and 22 other honey samples for clopyralid. Pyrrolizidine alkaloids were detected in 20 per cent of the samples, but predominantly at low levels (