Well, i know you wouldn't want to mix plastic with anything
hotter than room temp, but diffusion with cold drinks is minimal
for hard plastics like Polypropylene that most ballpoint pen barrels consist of.
Polypropylene (PP)
https://www.acplasticsinc.com/informationcenter/r/fda-approv...Polypropylene is most often used for single-serve containers like yogurt cups, but also shows up in reusable containers that can store leftovers. On top of being one of the FDA approved food contact materials, it's microwave safe and nonvolatile, meaning it will not react with any type of food you store in it, whether it's acidic, basic or liquid.
