Most synthetic veterinary drugs - including antibiotics and growth hormones - are prohibited under organic regulations. (whfoods.com)
The USDA organic regulations recognize the risk of heavy metal contamination at § 205.203 (c): «The producer must manage plant and animal materials to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances.» (rodaleinstitute.org)
Furthermore, organic growers and handlers are inspected at least once a year, and ingredients and products can be tracked from the farm to the grocery store shelf because of the traceability requirements included in organic regulations. (foodsafetymagazine.com)