I'd long since noted that as the jar emptied the grinders were increasingly ineffective. Thinking on why that might be ... I realised that this was because as you grind the pepper, you're also grinding plastic directly into your food.
There's surprisingly little discussion about this that I can find, though this 5 y.o. Stackexchange question addresses the concern:
<https://cooking.stackexchange.com/questions/103003/microplas...>
Seems to me that plastic grinders, whether disposable or sold as (apparently) durable products, are a class of products which simply shouldn't exist.
Searching, e.g., Walmart for "plastic grinders" turns up five listings presently, though it's not clear whether it's the body or the grinder itself which is plastic. In several cases it seems to be the latter.
<https://www.walmart.com/c/kp/plastic-grinders>
(Archive of current state: <https://archive.is/yIIX4>