On the Unfounded Fears of Coffee Contamination

Coffee is, in many ways, a magical drink. It tastes delicious, it wakes us up, and—as decades of scientific research tells us—it also has a variety of health benefits. “Overall, the consensus is that moderate coffee intake is more beneficial than harmful across a wide range of health outcomes”, as one comprehensive 2025 literature review put it.

And yet, for all that coffee is lauded for its healthfulness, it has also attracted concern about its potential harms. Are the chemicals used to decaffeinate coffee safe? What about the compounds created during roasting? Oh gosh, what about mould?

Within the last decade, the wellness industry and its online influencers have increasingly pushed fears about contaminated coffee. Much of their ire has centred on mycotoxins, naturally occurring toxins that are produced by certain moulds and fungi. They’re found in a wide range of food products, including cereals, nuts, dried fruit, meat and dairy products—and coffee. Other contamination worries concern heavy metals and pesticide residue.

Scientists have researched mycotoxin levels in coffee for many years, and found that, yes, there are low levels in some coffees. But, in general, they remain far below government-mandated limits, and are most often present in the cheapest commodity beans. When consumer advocacy groups have investigated other contaminants, their findings have been similarly tame.

And yet, that evidence hasn’t done much to slow the discourse around coffee’s supposed harms. Of course, we all want to know that what we’re consuming is good for us, or at least not actively harmful. But the fear of mycotoxins in coffee has, in a basic sense, been manufactured. It’s worth asking: Who does this fearmongering really harm?

Coffee and Mycotoxins

When people talk about mouldy coffee, they are mostly referring to several mycotoxins that can grow on green or roasted coffee (as well as countless other food products). Humid, damp, and warm conditions at any stage in coffee’s production—including during post-harvest, processing, storage, transportation, or after roasting—can cause mycotoxins to grow. Of these, Ochratoxin A (OTA) is considered the most prevalent, and is the only mycotoxin for which regulatory limits have been established in coffee.

Throughout history, fungi and their mycotoxins have had a big impact on human health. Despite improvements in food safety, mycotoxins can still be harmful in high enough concentrations, and possibly even carcinogenic. Risk to humans from OTA has not been proven, however, with one 2015 review noting that “there appears to be no statistically significant evidence for human health risks associated with OTA exposure”.

Permissible OTA levels in food depend on the country, and not every country has legal limits. The European Union does have regulations that cover maximum levels of safe OTA exposure in coffee: Since 2023, it has been 3 μg/kg (that’s micrograms per kilogram) for roasted coffee, and 5 μg/kg for instant coffee. (Previously, the permitted levels were 5 and 10 μg/kg, respectively. The United Kingdom continues to enforce these pre-2023 levels.) 

Dozens of studies over the years have examined mycotoxin levels in green, roasted, and brewed coffee. In all these studies, the levels found were far below the EU’s threshold. Additionally, studies have shown that roasting coffee reduces OTA levels significantly. Moreover, because the final cup of brewed coffee generally contains less than 2% total dissolved solids, the amount of OTA you are actually at risk of consuming from coffee each day is miniscule. 

A 2021 review (financed by the National Coffee Association) found that “no evidence was identified from historical data to suggest OTA is acutely toxic in humans from coffee consumption or other exposure sources”. Another review in 2024 had similar findings, noting that “the OTA content of coffee is not toxic to consumers worldwide”.

Because mycotoxin fears continue to percolate among consumers, people working within the coffee industry have also looked into the question. In a 2016 series, Chris Kornman of Royal Coffee estimated that a 150lb adult “would have to drink over 2 liters of brewed coffee per day to risk toxicity levels, roughly 11 eight-ounce cups. Per day. Every day”.

In a recent video, the YouTuber and author James Hoffmann ran his own tests on the presence of OTA and heavy metals in various coffees, from commodity-grade to high-end specialty, as well as some unnamed healthy-branded coffee. Hoffmann tells me he had read up on the subject before, but wanted to do his own tests because “I felt like there was a value in addressing it directly rather than by referencing the research”.

His team sent samples for lab-testing. The results? “The levels of heavy metals and mycotoxins were incredibly low in all the products we tested, from cheap supermarket coffee to specialty coffee”, Hoffmann says. OTA levels for every coffee were less than 0.5 μg/kg, far below the E.U.’s limit. Other coffee companies have done similar tests, with similar results.

They didn’t test the very lowest-cost coffees available, and Hoffmann theorises that those may have shown higher levels. “However, the reasons not to drink the cheapest coffee are many”, he says, and “even if the concerns about mycotoxins or heavy metals are unfounded, cheap coffee comes at too high of a human cost for me to freely recommend it”.

Downward Pressure

There is also a human cost to this drummed-up panic about coffee contamination—but it’s not consumers who are at risk. Instead, it’s coffee farmers who are forced to bear the burden of this fearmongering.

Coffee farmers already face enormous downward pressure from the consuming side of the supply chain. There is pressure to produce the highest-quality coffee for the lowest possible cost (even when the majority of smallholder farmers continue to live in poverty, often producing coffee for below the cost of production). Consumers expect their coffee to remain cheap, and any rise in retail prices makes headlines around the world.

As well as price, consumer-side coffee trends—like the growing interest in elaborate fermentations and high-end varieties—even if well-meaning, put additional pressure on the producing side. Lucia Solis, a fermentation expert and consultant who works with coffee producers around the world, uses the analogy of the butterfly effect. Even small changes in consumer preference can end up impacting those growing the coffee. “I feel like a lot of consumers don’t realise how strong their impact is”, she says.

The focus on mould and mycotoxins is yet another example of this burden. “There’s this downward pressure on producers to change their processing, to do something different, and it’s that vulnerable part of the supply chain that doesn’t have the resources to do it”, Solis continues. “It’s still not accessible for producers to test their own coffee”.

In 2001, as consumer concerns about mycotoxins in coffee were increasing, the International Coffee Organisation and the United Nations Food and Agriculture Organization launched a five-year project to assess the OTA risk in coffee production, and suggest improved practices along the supply chain.

As part of this project, the two organisations undertook a number of socio-economic studies in producing countries to understand the realities of implementing such practices on the people most affected. In the conclusion to the Uganda study, the authors wrote that:

Today, it is increasingly difficult for farmers to guarantee a stable income due to substantial fluctuations in coffee prices. Prices have declined so much that even renewing a plantation, or its upkeep, can be problematic. Under such conditions, it is difficult to speak of “good agricultural practices”. Yields and volumes are declining due to the appearance of wilt disease, input prices increase regularly, the cost of basic household requirements is growing. Under these conditions, the worry is not so much to guarantee the quality of a product (consumed elsewhere) as to produce coffee whilst reducing the costs and resources used, and ensure the survival of the household and the schooling of its children, etc.

That was written in 2006, but 20 years later, not much has changed. The commodity market goes up and down, and yet the majority of farmers still struggle to make ends meet. Amidst these existential pressures, Solis points out that most smallholder farmers just don’t have the time, resources, or inclination to worry about mycotoxins.

Others I spoke to echoed this sentiment, as well as skepticism that the onus should be placed on smallholder farmers to change their techniques—particularly when OTA growth remains a low-priority concern within specialty coffee. Where researchers have found noticeable mycotoxin contamination, Solis, Hoffmann, and others told me, they have come from the cheapest coffee grown on the biggest farms.

Panic! At The Coffee Roastery

There are parallels between the current fearmongering over mycotoxins and the 2010s acrylamide panic. In 2010, the Council for Education and Research on Toxics (CERT)—a “secretive nonprofit”, according to Ars Technica, which has reportedly made millions from lawsuits—sued some 90 coffee roasters and retailers, including Starbucks and Folgers. CERT claimed that acrylamide, a scary-sounding compound that is created during the coffee-roasting process, is carcinogenic and thus needed a warning label.

The lawsuit stemmed from California’s Proposition 65, a 1986 law that seeks to advise consumers about the risks of certain chemicals to human health. Similarly to mycotoxins, there is a chance that acrylamide might cause cancer, but—again, like mycotoxins—the dose makes the poison. As Liz Clayton wrote for Sprudge in 2022, a cup of coffee contains about 0.45 micrograms of acrylamide, while a serving of fries contains between 39–82 micrograms.

In 2018, a judge in California ruled that retailers had to print a warning on every bag of coffee sold in the state. A year after the judge’s ruling, however, California’s Office of Environmental Health Hazard Assessment officially removed coffee from the state’s cancer warning list.

The U.S. coffee industry celebrated—“This is a great day for science and coffee lovers”, as National Coffee Association CEO William “Bill” Murray put it—but the problem didn’t really go away. Instead, we just realised that acrylamide in coffee is really not that big of a deal, and stopped talking about it as much (although it’s still a topic of discussion on social media and wellness-related websites).

Concern about mycotoxins in coffee feels, to me, like a similar red herring. Still, it remains such a hot-button issue that a number of coffee companies have published blog posts debunking the claims. Sometimes, these posts are prompted by a customer getting in touch because they “heard that coffee is mouldy”.

Ultimately, much like acrylamide, or heavy metals, or any other contaminants, mycotoxins can be as big or as small a problem as we decide to make them. Research has consistently shown that the levels of OTA and other contaminants in coffee are extremely low, while there are hundreds (thousands?) of studies at this point showing that coffee is good for us.

The reality is that you can walk down the street and inhale car exhaust, or stand next to someone smoking a cigarette, and be exposed to far worse than what’s in your morning beverage. Heck, wood-burning stoves are incredibly harmful, but you don’t see wellness influencers discussing that very often.

Coffee remains an unequal industry, one where power is massively skewed towards consumers and away from farmers. Misplaced concerns over mycotoxins and other contaminants may be a passing fixation for consumers, but they translate to significant pressure for already-burdened farmers. Ultimately, they’re just one more symptom of the coffee industry’s imbalance.

Header image by Tom Winchester®️ via Pexels