That’s a good question. No, they are not inert. The plastics used in these liners are known to be endocrine disruptors. Some of them, for example, are close enough in structure to estrogen to do a good job of functioning like that hormone in the body. Many scientists advise avoiding them, but of course industry pushes back (not with data, but with political clout).
Here is a longish article that cites references for further exploration: