Most of the apples in grocery stores have been in storage for months since most are harvested in fall and have been sprayed with diphenylamine (DPA), an antioxidant that slows the development of black patches on the skin. DPA is banned in the EU because a byproduct of it when it breaks down, nitrosamine, is a carcinogen.

I love apples, but since finding this out, I try to avoid eating them out of season.

This article fails to mention DPA, but is interesting nonetheless! https://www.npr.org/sections/thesalt/2018/11/26/668256349/th...