- polyethylene oil?
- gas?
- natural gas?
- wax (I'm assuming candle wax)?
I understand you don't mean "drink" when you say our body "handles" it, but you do realize we don't make food from PET, nor do we usually "handle" gas and natural gas in any form of direct contact?*
* with the fun exception of a brief craze in my high school years where people would mix hard alcohol with gasoline to make cocktails "stronger". That's another story though
It's the same way that, even though you shouldn't drink it, acetone is barely toxic, because your body knows how to process it.
I should remind you that there are other plastics, but polyethylene is not one of the toxic ones.
(Gas, as in gasoline, has benzene which is a different category. Note also that many plastics have plasticizers which are also a different category, although polyethylene rarely has any, it's possible that it could.)
Both are made from Polyethylene, which is the exact same stuff oil (including food), gas, wax, natural gas, etc is made off. i.e. you body handles that all the time.