I’m curious about how often heavy metals are detected in flower/trim/concentrates etc. Since hemp and cannabis are bioaccumulators, it seems like low levels of heavy metals (especially in outdoor grows) could be relatively common. However, I live in a state (WA) where heavy metals testing for recreational products is not yet required, so I have no idea how prevalent heavy metals truly are.
What has been your experience?
Typically even if you see heavy metals in plant material they will not extract. Complete opposite of pesticides.
Curious. Not unreasonable. How are folks failing in concentrates then?
We had outdoor MJ plants fail for lead and arsenic before… Had some fail just recently actually. Didn’t fail badly, but still failed.
This is the first time we have ever seen it happen though. It was also the first crop on this specific plot, and only a small section of the plot failed for Heavy Metals… we are still trying to figure out what caused it.
this is where “CRC” techniques can really come in handy though. Different powders/clays can help to remove at least some of these heavy metals during extraction.
I would imagine it is primarily from contamination from the equipment or supplies used in extraction. Some solvents are also much more likely to extract metals (see halocarbons)
On the growing side, it can happen for a couple reasons.
First is foliar application with an organic amendment like azomite that is above FDA limits for consumption of lead, arsenic, etc. It is in a soluble metal salt that can bioaccumulate.
The second is soil that is high in heavy metals. I did a soil test on a farm that was high in Aluminum and guess what- their flower failed for heavy metals too. This can be remediated with a calcium source like gypsum which neutralizes the cation exchange of aluminum and other heavy metals. The second is a high fulvic additive (shameless plug for my company) Both of these don’t allow heavy metals to bioaccumulate.
Toxic Minerals-2020.pdf (236.5 KB)
Or potentially add them one might imagine…
very true…
we haven’t seen that happen yet though. But we also haven’t had much hot material so…
I spent the last two years researching and writing a book on this topic: :Measuring Heavy Metal Contaminants in Cannabis and Hemp, published by CRC Press. A great read if you are interested in getting a better understanding of sources of heavy metals in cannabis consumer products.
How do you feel about using the ionic charge in calcium and humates to help remediate soil with heavy metals?
I can say with confidence HMs can be extracted and will show up in HM tests.
My lab had to cut ties with a couple of grows due to consistent HM levels. When we blasted in-house flower on the same equipment with the same purging methods there would never be any HM results. When we would blast a select few grows that sold us trim we would consistently pop for HM at some level.
It was clear cut and easy to plot that some grows flower had HM contaminants in it and others did not. Our testing coordinator built a spreadsheet and after weeks of testing with various grows it was obvious some places were “cleaner” than others.
This is what I was going to say, if it was in aerosol form, yes it’s a problem, if it came from the soil, and is IN plant material, it’s not as much of a concern, but still, a concern…
Yes, it should work. The process of heavy chelation is well understood…it is the fundamental principle behind chelation therapy, where the calcium salt of ethylene diamine tetra acetic acid (EDTA) is injected into a patient with elevated blood lead levels. The anionic ligand groups of the EDTA bind to the large Pb cations and are excreted out in the person’s urine. Same principle with chelating agents like humic acid, which is a high molecular weight organic molecule that has reactive anionic sites like EDTA. As long as the Pb is in solution, the Pb cations will bind to the negative sites of the humic acid. However if the Pb is extremely high, such as in a toxic waste site, the process grinds to halt because the humic acid gets saturated with Pb. Hope this helps?
Absolutely. The CSO for AgTonik is a PhD Biochemist. This aligns perfectly with our research that we have done. I’m going to suggest he pick up your book.
Thanks for the plug AgTonik…very much appreciated. FYI there are other ways to reduce heavy metal uptake. Another way is increasing the soil pH (making it less acidic) by treating it with lime (CaOH) or limestone (CaCO3). This will reduce the level of heavy metal ions in solution and therefore less available for plant roots to absorb. However, you don’t want to make it too alkaline, because it will reduce the absorption of the essential minerals such as phosphorus (phosphates) potassium and nitrogen (nitrates) and other trace nutrients like iron, and other transition elements. Another way is to use a filtration approach using activated carbon. Biochar is one of the most common of these chemicals which is made from any biomass material (plant storks, tree branches, nut shells) by heating to a low temperature (approx 500 C) in the absence of oxygen to make a charcoal-type material, which is then mixed in with the soil. This then filters out the heavy metals and reduces uptake by the plant.
Cannabis is a heavy metal accumulator. Hemp can be used to restore terra to a usable state after contamination occurs.
@heavymetalguru is the biggest source of heavy metals in indoor grows coming from the water they use? I know denver county had to raise the ph of their public water system after they started testing for heavy metals in the rec market 2 years ago because of lead content.
Possible but unlikely unless the local water authority is not treating the water correctly based on its chemistry (pH, dissolved solids, organic content etc). If lead pipes are being used (think Flint, MI), you have to add a soluble metal phosphate (sodium or ammonium) to the water supply, which forms a layer of phosphate on the inside of the lead pipes to stop them corroding. This is what they failed to do in Flint, MI, when they changed the water supply from Lake Huron to the Flint River and didn’t check the different chemistry. As a result the water slowly dissolved the lead pipes and contaminated the drinking water with lead. EPA maximum contaminate limit for lead is 15 ppb…Flint had over 5000 ppb lead. Suggest you get the water tested for Pb and other heavy metals and check them against the EPA primary contaminant list. BTW, another possible source of heavy metals is from the fertilizer or nutrient. They are often made from low quality fertilizers made from phosphate which are typically high in heavy metals. Hope this helps
I couldn’t edit my post about Denver adding to the ph so here is my source^^
It doesn’t mention anything about weed testing being an identifier but it happened within a month of mandatory HM testing so I guess I put 2 and 2 together.