No, never. Two reasons: 1. If the vegetable is in good unblemished condition I tend not to peel it, and, as you say, on commercially grown veges the skin has residues of pesticides, fungicides, anti-sprouting chemicals etc. 2. I don't use vege stock when I cook as I find it makes everything taste like overcooked hospital food. I use home made chicken or lamb stock when I need stock.