When we cares about the purity of nootropics,here is the one most people will ignore but it will be always exists in your nootropics,especially nature ingredients.
eavy metals, such as cadmium (Cd), chromium (Cr), arsenic (As), lead (Pb), nickel (Ni), and stannum (Sn), are a group name for metals that have been associated with contamination and potential toxicity. The soil, water and air are contaminated by these heavy metals, which directly effect agricultural crops through cultivation. Consumable heavy metals from contaminated agricultural crops on a long-term basis can accumulate in plant crops, and therefore in animals which consume the crops. Once accumulated in animals or crops, to decontaminate or excrete can be difficult, even though the immobilizer-assisted management skill is suggested for removing metal-contaminated agricultural soils for safer food production.
Toxic heavy metals are clearly harzadous to humans. Cd is well-known to cause damage to kidneys and bones as well as DNA damage and mRNA transcriptional changes in the gills of Mytilus galloprovincialis . Pb poisons create physiological and morphological responses in microalgae. Some heavy metals also cause toxicity-related mutagenesis and carcinogenesis . Inconveniently, the sign and symptoms of contamination by heavy metals do not appear early or easily, especially in humans. Therefore, heavy metal contamination on the human body has been of great concern.
Heavy metals may be introduced during manufacturing or by natural means because of the ubiquitous problem of soil and water pollution in certain regions. High levels of lead and cadmium have been found in some herbal medicines.Furthermore, minerals or other adulterants may be added to traditional medicines for therapeutic purposes. Cadmium, lead, mercury, and arsenic have been identified in this context.Details of nephrotoxicity resulting from heavy metal ingestion can be found in textbooks related to poisoning and drug overdose.28
So now you will know that is why heavy metal data of herb extracts data higher more than synthetic compound.The maximum lvels (mg/kg wet weight) of food supplement of EU standard is 0.1mg/kg.Here is the link https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CONSLEG:2006R1881:20100701:EN:PDF
You can check with your COA,normally the data will be under 10ppm,which same with 10 mg/kg.Of course the low heavy metal ,the better.The fact is each data of metals will be under 2ppm which is normally acceptable.