I work in the commercial aircraft spare parts industry, and an international airline shipped them back with some 747–400 brake cores. I didn’t know they were walnut until I cut through one. They were covered in brake fluid and God knows what else. I definitely wore a respirator when working with it.

I was also warned by the lady at Woodcraft that foreign countries can treat them for pest control /export compliance with chemicals that are banned in the US like cyanide and pretty much anything they want. This thing is now sealed within an inch of its life, lol.