Slate published an interesting article about the "dirty secret" of organic farming recently. I'm not going to spend a lot of time describing it to you (it's almost 10 p.m. and I just finished my classwork for the day and I want to go to bed soon), but suffice it to say that organic fields often feature soils nearly as polluted with heavy metals (and in some cases more) than fields treated with traditional pesticides and chemical fertilizers. Go ahead and read the article. It really is pretty interesting.
This was a bit of a surprise to me, but it's actually pretty logical. Organic fertilizer often includes the waste of animals. Animals excrete the trace heavy metals they pick up from their environment through their waste. Putting that waste onto your fields is putting a concentrated version of all the heavy metals in the food those animals ingested into your soil.
You know those weird people who seem to be offended anytime people recognize problems in the world and then try to fix things? You know there are going to be talking heads, if this story finds wide circulation, who will use this as ammunition against organics. I don't think it should be an all-or-nothing game, though. My first reaction isn't "Well, that just shows the whole idea is stupid; let's go back to petroleum-based fertilizers and chemical pesticides." My first reaction is, "Is this really an issue? Do the foods pick up enough of the metals in the soil to pose a health risk?" followed by "Perhaps this is just a sign that it's time for increased research to design the best organic fertilization methods and/or products to decrease this negative side effect."
Too bad I'm not an agricultural scientist with a dual degree in organic chemistry. I'd shake up the organics work with my mad whack innovations instead of just feebly typing about it to an audience of three.