There are no toxic chemicals used in the production of D3 and there are no such chemicals in the finished material. A pharmaceutically pure nutrient such as vitamin B1, vitamin D3, and biotin cannot be certified organic because they are synthesized. It must meet USP standards, that is, very precise requirements for purity. It is incumbent upon us to buy good material, and we do. Certainly, a disreputable supplier might try to slip contaminated material into the marketplace, but requirements for the manufacturer, raw material seller, and buyer to test the material for heavy metals and pesticide residues closes the door on such materials ever legally making it into the U.S. marketplace. If noxious substances are present in the material they will be detected somewhere along the line.
In order to qualify as a pure nutrient, by definition there may be no other molecular substances present in it other than waters of hydration, and, occasionally, mineral ash measured in fractions of parts per billion or parts per million. In other words, these compounds must essentially be 100% pure.