Pesticides are mentioned as a possible cause for the nicotine, as well as the drying process. The nicotine was detected in dried Boletus Edulis, but also in truffles and chanterelles. Most of the mushrooms with nicotine were imported from China, but also wild mushrooms from other countries were affected. Nicotine is a naturally occurring alkaloid in tobacco. Low concentrations are also found in other plants such as tomatoes, aubergines, peppers and potatoes.

Insecticide
Nicotine is used as an insecticide. In European countries, the use of plant protection products containing nicotine will phase out by June 2010, but its use in other countries may continue and lead to residues of the substance in food.
Nicotine is acutely toxic by all routes of exposure (oral, dermal and inhalation). It targets the peripheral and central nervous systems causing for example dizziness, salivation, increased heart rate and blood pressure.
Due to these findings, EFSA is recommending a lower MRL for wild mushrooms.