Tansy: Influence of Cooking on Toxicity

Tansy oil seems to be toxic in high doses. In my region in Belgium we eat regularly tansy cakes without harm. Is the thujol being detoxicated by heat?

Thujol is better known as thujone. It is a naturally occurring monoterpene found in a variety of plants, most notably wormwood species (Artemisia spp.). It has long been implicated as a key cause of mental disturbance among absinthe drinkers around the turn of the 19th century. Most famously, Vincent Van Gogh was said to have suffered hallucination and excitation as a result of his addiction to absinthe. Thujone was subsequently banned from absinthe products. A recent study, however, suggests that thujone concentrations in wormwood may not be high enough to be much of a factor in absinthe (https://socrates.berkeley.edu/~mcb165/lachenmeier_2005_thujone.pdf).
James Duke's Dr. Duke's "Phytochemical and Ethnobotanical Databases" reports that tansy leaf has 1124-3500 parts per million thujone. This compares to wormwood's 1750 parts per million. Although we cannot automatically assume that thujone is the sole culprit responsible for tansy oil's toxic effect, if it is indeed the sole culprit then baking would remove the toxic effect. That true because the boiling temperature of thujone is only 86 degrees Celsius, so baking at normal oven temperatures should remove most or all of the thujone. Prolonged boiling should do the same.