Creosote is classified as a probable human carcinogen by the EPA

https://fair-wiki.win/index.php/Local_Roofers_in_New_York_Share_Their_Favorite_Asphalt_Shingle_Projects

Creosote is classified as a probable human carcinogen by the EPA. Long-term exposure may increase the risk of certain cancers, making awareness and precaution essential for those in contact with treated wood.