3% same as "food grade"?

hi,

the post below raised a question i am unclear on - is the 3% h2o2 you get at walgreens the same as the expensive "food grade" stuff, only just more watered down? someone told me the cheap stuff from the drug store has contaminants in it, does anyone know if that is true? i think ed mccabe sells some affordable food grad stuff on his site. any input would be appreciated.

thanks

ff