Heavy Metals, Pesticides and Mold in Mushroom Products
What published studies found about metals, pesticide residues and microbes in mushrooms and mushroom products, with the limits of each study and no brand names or safe-amount claims.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Mushrooms take up substances from what they grow on, and that includes metals. This page summarizes studies we read on metals, pesticide residues and microbial load in mushrooms and mushroom products. Most studies are of food mushrooms, a few are of supplements, and none tells you that a particular bottle is safe or unsafe. It names no brands.
This page is about products. If you or someone else has eaten a wild mushroom, call Poison Help at 1-800-222-1222 in the US, or 911 for collapse, seizure or severe vomiting with confusion. See Plant and Mushroom Poisoning.
Information here is for general education. It is not medical advice.
Why mushrooms are mentioned in metal studies
A review of the chemistry of wild and cultivated mushrooms says that several species can accumulate very high levels of detrimental trace elements, particularly cadmium and mercury, if growing on heavily polluted substrates. [1] Where and how a mushroom is grown therefore matters, and results for one species or site do not transfer to another.
What studies found
| Question | What the study found | Strength of evidence |
|---|---|---|
| Metals in commercial supplements | In Serbia, preparations labeled as Cordyceps sinensis, Ganoderma lucidum and Coprinus comatus were analyzed. Lead ranged 0.130 to 0.360 mg per kg, cadmium 0.09 to 0.39 mg per kg, and arsenic below 0.03 to 0.46 mg per kg. [2] | Small survey, 2014, one country |
| Metals in dried food mushrooms | A study of 164 commercial dried mushroom samples from Poland found most median levels within the safety thresholds the authors used, but also one extreme arsenic outlier and large differences between producers. [3] | Food mushrooms, one market |
| Organic vs conventional | In the same Polish study, certified samples showed lower mercury and arsenic. [3] | One study; certification type matters and is not defined here |
| Reishi eaten in a producing region | In Longquan, China, the overall risk from metals in G. lucidum was described as relatively low, with higher risk potential for arsenic and chromium needing speciation tests. [4] | Local exposure model, not a product test |
| Arsenic in wild caterpillar fungus | Wild Cordyceps sinensis (now Ophiocordyceps sinensis) had total arsenic of 5.77 to 13.20 micrograms per gram, and inorganic arsenic made up 4.47 to 11.42% of the extracted arsenic. [5] | Wild samples; not cultivated Cordyceps militaris |
| Bioaccumulation by wild edible species | In Croatia, all ten species examined were bioaccumulators of cadmium and mercury. [6] | Food mushrooms, one region |
| Pesticide residues | Of edible mushrooms tested for 62 pesticides, nearly 20% of samples had one or more residues, and some varieties exceeded limits. The authors did not find an unacceptable risk, even in the worst case. [7] | Edible mushrooms, not supplements |
| Microbial load | A study of shiitake products found high yeast and mold counts in locally bought mushrooms. [8] | Food products, 2016 |
| Mold toxins in mushroom supplements | Proper evidence not found. We searched PubMed for mycotoxin and mold-toxin testing of mushroom supplements and found no study in the sources we read. | Not assessed |
What this does and does not mean
- A study of food does not describe a supplement. Extracts, powders and capsules can concentrate or remove components, and the studies above do not tell us how metals behave in each form.
- A low result in one batch is not a guarantee. Levels varied between suppliers in the Polish study. [3]
- Wild-harvested products add an uncertainty. The arsenic findings come from wild caterpillar fungus, and the review links accumulation to the substrate. [5] [1] For conservation questions see Wild Harvest, Conservation and Sustainability.
- Safe daily limits are not given here. The sources above compare results to thresholds chosen by the authors. They do not give a limit for a reader to use.
Who should be especially careful
The sources on this page do not describe who is at higher risk from metals in mushroom products. General guidance is in Heavy Metals in Supplements and Herbal Products, Pregnancy and Breastfeeding and Children and Teens. People with kidney or liver conditions, pregnant or breastfeeding people, and children should ask a pharmacist or clinician before using any mushroom supplement. See also Mushrooms and the Kidneys, Oxalates and the Liver. For testing, see Quality Testing and Certificates of Analysis.
Frequently asked questions
Do mushrooms contain heavy metals?
They can. A review says several species can accumulate very high levels of cadmium and mercury when growing on heavily polluted substrates. [1] Levels in the supplements and dried mushrooms we read varied by species, producer and region. [2] [3]
Are organic mushroom products lower in metals?
In one Polish study of dried food mushrooms, certified samples had lower mercury and arsenic. [3] Proper evidence not found for mushroom supplements specifically: we searched PubMed for organic versus conventional supplement testing.
Is arsenic in cordyceps a concern?
Total arsenic was measured in wild Cordyceps sinensis samples, and most of it was not the inorganic form. [5] The sources we read do not say what this means for a person using a product, so ask a pharmacist or clinician.
Can mushroom supplements contain pesticides?
Edible mushrooms in one study had residues in nearly 20% of samples, and some exceeded limits, though the authors found no unacceptable risk. [7] Proper evidence not found for supplements specifically.
Is a product with a lab certificate free of contaminants?
Not automatically. A certificate covers only the tests it lists. See How to Read a Mushroom Supplement Label and the testing page above.
References
- A review of chemical composition and nutritional value of wild-growing and cultivated mushrooms. J Sci Food Agric 2013 Read 2026-10-23.
- The level of elements and antioxidant activity of commercial dietary supplement formulations based on edible mushrooms. Food Funct 2014 Read 2026-10-23.
- Evaluation of Toxic Elements in Commercial Dried Mushrooms from the Polish Market: Exposure Assessment and Health Risk Characterization. Molecules 2026 Read 2026-10-23.
- Risk assessment of potentially toxic elements exposure through ganoderma lucidum consumption in the population of Longquan, China. Environ Geochem Health 2025 Read 2026-10-23.
- Arsenic Content, Speciation, and Distribution in Wild Cordyceps sinensis. Evid Based Complement Alternat Med 2021 Read 2026-10-23.
- Lead, cadmium and mercury contents and bioaccumulation potential of wild edible saprophytic and ectomycorrhizal mushrooms, Croatia. J Environ Sci Health B 2017 Read 2026-10-23.
- Pesticide Residues in Edible Mushrooms: A Health Hazard? J Agric Food Chem 2026 Read 2026-10-23.
- Evaluation of Microbial Loads on Dried and Fresh Shiitake Mushrooms (Lentinula edodes) as Obtained from Internet and Local Retail Markets. Food Saf (Tokyo) 2016 Read 2026-10-23.