[sampo]

Caprolactam used to be the the only chemical IARC had ever classified in their group 4 "probably not carcinogenic to humans" [1] but in 2019 they moved it to group 3 [2].

[1] https://publications.iarc.fr/_publications/media/download/22...

[2] https://monographs.iarc.fr/list-of-classifications/