There are over four hundred known mycotoxins. The food science literature is enormous. Coffee, as a category, sits in a moderate-risk zone, lower than peanuts or maize, higher than meat or dairy.
For most coffee drinkers, four toxin families cover the actual conversation. The first two account for nearly all of the regulatory and consumer-side concern. The second two are less prevalent in coffee specifically but show up in adjacent literature often enough that they deserve a paragraph.
Here is each one, what produces it, why it ends up in coffee when it does, and what the research and the regulators have said.
1. Ochratoxin A (the headline mycotoxin)
Producing fungi: Aspergillus ochraceus, A. carbonarius, A. niger, Penicillium verrucosum Where coffee picks it up: Post-harvest, during fermentation and drying, in warm and humid conditions.
Ochratoxin A is the mycotoxin most associated with coffee. It is also the one with the most regulatory infrastructure built around it. The European Union enforces a maximum level of 5.0 µg/kg in roasted coffee and 10.0 µg/kg in green coffee under Regulation (EU) 2023/915. The United States has no equivalent limit.
In animal studies, Ochratoxin A is nephrotoxic, immunosuppressive, and at sufficient dose, teratogenic. The International Agency for Research on Cancer classifies it as Group 2B, possibly carcinogenic to humans. In human epidemiology, the strongest associations are with chronic kidney disease in geographies with historically high dietary OTA exposure. The European Food Safety Authority’s tolerable weekly intake is 120 nanograms per kilogram of body weight.
Our deeper read on OTA is in Ochratoxin A: The Coffee Toxin Nobody Talks About.
Our Eurofins assay for the green decaf returned a result of less than 2.0 µg/kg, below the laboratory’s detection limit. The pillar post with full methodology is here.
2. Aflatoxins (the most carcinogenic of the bunch)
Producing fungi: Aspergillus flavus, A. parasiticus Where coffee picks them up: Improper drying or warehouse storage, particularly in warm humid climates. Less common in coffee than in peanuts, maize, or tree nuts.
Aflatoxins are produced as a family. The four most commonly assayed are B1, B2, G1, and G2, named for their fluorescence under UV light (blue or green). Aflatoxin B1 is the most toxic and the most studied. The World Health Organization classifies aflatoxin B1 as a Group 1 carcinogen, the highest category. It is one of the most carcinogenic naturally-occurring substances known.
In coffee, aflatoxin prevalence is lower than Ochratoxin A. Coffee is a less hospitable matrix for A. flavus than peanuts or corn. Surveillance studies in green coffee have found aflatoxin detection rates in the 5% to 15% range across regions, with quantitative levels generally well below the United States’ FDA action level of 20 µg/kg for total aflatoxins in human food. Most positives cluster at low single-digit µg/kg.
That said, aflatoxin contamination in coffee is real and worth screening for. The assay is well-established (USP 561 Method 3 or AOAC 991.31), and the cost is on the order of a few hundred dollars per sample.
Our Eurofins test returned all four aflatoxins (B1, B2, G1, G2) below the lab’s detection limit of 5.0 µg/kg each, well under the FDA action level.
3. Fumonisins (lower risk in coffee, common in adjacent literature)
Producing fungi: Fusarium verticillioides, F. proliferatum Where coffee picks them up: Rare. Fumonisins are primarily associated with maize and grain crops. Their occurrence in coffee is sporadic and at low concentrations.
Fumonisin B1 is the most-studied member of the fumonisin family. The IARC classifies it as Group 2B (possibly carcinogenic). The strongest human-health associations are with esophageal cancer in regions with high dietary maize fumonisin exposure and with neural tube defects in maize-dependent diets.
In coffee, fumonisin contamination has been reported in some surveillance studies, particularly in green coffee from certain producing regions, but concentrations are typically far below the FDA’s guidance levels for maize-based foods (2.0 to 4.0 mg/kg in finished products). Coffee is not a meaningful dietary source of fumonisin for the general population.
The reason fumonisins appear in coffee-and-mycotoxin discussions at all is that comprehensive mycotoxin testing panels often include them by default, and “non-detectable for fumonisins” reads well in marketing copy without being especially informative. If a brand cites fumonisin testing prominently in their coffee transparency claims, the test is real but the implication is somewhat overstated.
4. T-2 Toxin and Zearalenone (very low risk in coffee)
Producing fungi: Fusarium sporotrichioides (T-2), Fusarium graminearum (zearalenone) Where coffee picks them up: Rarely. Both are predominantly cereal grain contaminants.
T-2 toxin is a trichothecene mycotoxin. It is toxic at low doses in animals, causing immunosuppression and hematological effects. The European Union has set guidance limits for T-2 and HT-2 toxins in cereals (50 to 500 µg/kg depending on the product). Occurrence in coffee is sporadic and at very low levels.
Zearalenone is an estrogenic mycotoxin associated with hormonal effects in livestock fed contaminated grain. Coffee is not a meaningful source.
Both are mentioned here because comprehensive testing panels include them, and a few biohacker-coffee brands have made marketing claims around testing for the full panel. The testing is real but the practical risk in coffee specifically is minor compared to Ochratoxin A and aflatoxins.
Where this leaves you
A short version.
If you are looking at a coffee brand’s testing claims, the two compounds families that should be tested are Ochratoxin A and the four aflatoxins. Together they account for over 95% of the legitimate mycotoxin risk in coffee. A brand testing only OTA is doing the most-important assay. A brand testing OTA and aflatoxins is doing the right test. A brand testing the full panel including fumonisins and trichothecenes is being thorough, which is fine, but the comprehensiveness is partly a marketing choice rather than a meaningful additional safety improvement.
What matters more than the breadth of the panel is the rigor of the testing. ISO 17025 accreditation. Named assays. Numeric detection limits. Sample-specific reports. We covered the criteria in detail in What “Mycotoxin Free Coffee” Actually Means.
The two-assay test we ran at Eurofins on our green decaf covered the high-priority compounds. Both came back below detection. The cost was $398.42 and the methodology is in our pillar post.
If you want a decaf with the testing on the record, Blueprint is the most-tested in our lineup and the easiest place to start.
Frequently Asked Questions
Which mycotoxins are most common in coffee? Ochratoxin A is the most prevalent and most regulated. Aflatoxins (B1, B2, G1, G2) are less common in coffee than in peanuts or maize but still warrant testing. Fumonisins, T-2 toxin, and zearalenone are uncommon in coffee specifically and primarily appear in cereal grain literature.
Are there limits on mycotoxin levels in coffee? The European Union enforces a 5.0 µg/kg limit for Ochratoxin A in roasted coffee under Regulation (EU) 2023/915. The United States enforces a 20 µg/kg action level for total aflatoxins in human food but no specific limit for OTA in coffee. Other markets have varying limits.
Does brewing remove mycotoxins from coffee? Brewing extracts some water-soluble mycotoxins into the cup at variable rates. Ochratoxin A is partly extracted into brewed coffee but the concentrations remaining in finished beverages are typically a fraction of the green coffee starting concentration. The primary determinant of cup-level exposure is the green coffee quality and post-harvest handling.
Should I worry about mycotoxins in my coffee? For most healthy adults consuming coffee from compliant supply chains, the dietary exposure to mycotoxins from coffee is far below the established tolerable intake levels. The legitimate concern is for chronic high consumption from supply chains without quality testing. The way to address that is to buy from brands that publish their testing.
Is decaf coffee higher in mycotoxins than regular coffee? Decaf is not inherently higher in mycotoxins than caffeinated coffee. The starting green coffee determines the level. The decaffeination process can reduce some surface contamination in water-based methods but does not fundamentally change the mycotoxin profile.
What to read next
- Is Your Decaf Tested for Mold? Most Aren’t.. The pillar post with our Eurofins methodology and full results.
- Ochratoxin A: The Coffee Toxin Nobody Talks About. A deeper read on the most common mycotoxin in coffee.
- What “Mycotoxin Free Coffee” Actually Means. The precise language to look for and the marketing claims to discount.
No Curfews is the editorial dispatch from Heist, a coffee company that thinks the second half of the day deserves better. We publish lab results, sources, and the occasional opinion. Join the list if this is the kind of thing you want in your inbox.