Subject: How does the container affect the food or drink I an consuming?

This question came up after finding out about food grade plastic. I assume that 
what makes some plastics food grade and others not are some of the additives in 
the plastic. But why should I care one way or another? I eat the food that is 
in the container, not the container itself.

If I get to consume part of the container, is this particular to plastics or 
true for other types of containers? Do I get to consume some chemicals from 
glassware, ceramics or clay? 

And now for an application specific question. I want to mix together a bunch of 
ingredients for making homemade beer. Due to the large volumes I need a fairly 
large container. One of those 20 litre paint buckets is a good size but it 
obviously is not designated as food grade plastic. Do I run a risk of 
contaminating my beer and myself? Or is the food grade plastic designation more 
a public safety perception thing (like life jackets in airplanes)?

Re: How does the container affect the food or drink I an consuming?