Rock Phosphate & Arsenic Concentrations?

The woman who volunteers in our community organic garden is hesitant to use solid rock phosphate as an organic source of phosphorous because she's afraid of arsenic poisoning. Does anyone have information on the levels of arsenic in rock phosphate and if so, are these levels significant enough to be of concern to organic gardeners who wish to use it as a fertilizer?

Thanks!

I had not heard of this, but check out the table in this article:

http://www.health.state.mn.us/divs/eh/risk/studies/fertrpt.pdf

It's pretty scary. I did not know that arsenic is a class A carcinogen. I knew it was poisonous, but not like that.

Thanks. I sent the article on to the person who makes the decisions. I've always used rock phosphate in my organic garden and have never given it a second thought. Hmmm....