Impurity

An unintended substance present in a material/mixture as manufactured that was not an intentionally used substance in the production of the material/mixture. It may originate from the starting materials or be the result of secondary or incomplete reactions during the manufacturing process. For example, a chemical substance as supplied in commerce that is 99.0% pure is a mixture of the pure chemical substance and 1.0% of impurities. https://healthymaterialslab.org/tool-guides/hml-resources