I believe they add arsenic to the feed because it's grain based and the arsenic is for rodent control. I could be wrong, but I know it's common practice to use arsenic (or mercury) in grain silos to kill rodents. Arsenic is only one of the many reasons I wouldn't touch factory chicken with a 20' pole.
I am printing that out to give my daughter who eats fast food chicken, thinking it's a healthier choice than hamburgers. Thanks for posting it.