Carrageenan, arsenic, and what's actually in your coffee
Independent lab tests found heavy metals and acrylamide in nearly every coffee sample tested — and carrageenan in your favorite bottled latte.
Emily Harper
Coffee is one of the most heavily lab-tested foods in America, and the results are not clean. But "not clean" splits into two very different problems, and most coverage of this topic blurs them together. One problem is unavoidable: coffee is a plant grown in soil, and soil contains trace metals. The other problem is a choice: what a company adds to a coffee drink after it's brewed, canned, or bottled. This year's testing data draws that line clearly — and the second problem is the one worth getting angry about.
The largest independent coffee test found something in every sample
In August 2025, the food-testing nonprofit Clean Label Project published one of the largest independent coffee studies to date: 7,069 individual lab tests across 57 products from 45 top-selling US brands, covering heavy metals, mycotoxins, pesticides, phthalates, and glyphosate residue. CNN covered the results the same week.
The headline numbers:
- Heavy metals — arsenic, cadmium, lead, or mercury showed up in every brand tested, though Clean Label Project found most detections fell under EU per-serving limits. Levels varied a lot by growing region: African-grown coffees tested lowest, Hawaiian coffees tested highest, which the researchers attribute to volcanic soil.
- Acrylamide — a byproduct of roasting — was found in 100% of samples.
- AMPA, the breakdown product of the herbicide glyphosate, turned up in 72% of samples (41 of 57) — including 100% of the organic coffees tested, despite glyphosate being prohibited in organic farming. Glyphosate itself was only detected in 2 samples, which suggests the AMPA is residual contamination from soil or prior land use rather than active spraying.
- Phthalates, plasticizers linked to hormone disruption, showed up in 70% of samples (40 of 57), concentrated in canned coffee and single-serve pods.
Clean Label Project's own conclusion is more measured than the raw numbers suggest: they classified coffee overall as one of the cleaner categories they test, since most contaminant levels stayed under regulatory thresholds. That's worth saying plainly, because it's the honest read of the data — the danger here isn't necessarily what's naturally in the bean. It's what gets added next.
Carrageenan is the part that isn't coming from the soil
Search interest in "carrageenan" dwarfs searches for "coffee heavy metals" or "coffee lead test" — people are already looking for this specific ingredient, and for good reason. Carrageenan is a seaweed-derived thickener used to stabilize dairy and plant-milk drinks so they don't separate on the shelf, and it shows up across the ready-to-drink coffee aisle:
- Starbucks bottled Frappuccino: check the label on an Oatmilk Caramel Waffle Cookie bottle and carrageenan is listed directly as a stabilizer, per PepsiCo's own SmartLabel ingredient disclosure (Starbucks' ready-to-drink line is bottled and distributed by PepsiCo under license). (Not every flavor uses it — the classic Vanilla Frappuccino uses pectin instead.)
- Dunkin' bottled Iced Coffee lists potassium phosphate and carrageenan among its "less than 2%" ingredients, according to CVS's published ingredient panel.
- Costa canned latte (the Coca-Cola-owned brand) lists natural flavors, cellulose gum, and carrageenan, per its Amazon product listing.
Carrageenan is FDA-approved and classified as generally recognized as safe. But a December 2024 study in Inflammatory Bowel Diseases exposed intestinal epithelial cells taken from Crohn's disease patients to carrageenan directly, and found it amplified the cells' inflammatory response — more so when the tissue was already inflamed — without changing gut permeability. It's a cell-culture study, not proof carrageenan causes Crohn's flares in the real world, but it's a specific, recent, peer-reviewed data point that directly contradicts "it's just seaweed, don't worry about it."
Then there's "natural flavors," which shows up on all three labels above. Under FDA regulation 21 CFR 101.22, "natural flavor" is a legally broad category — it covers the flavoring extract itself, but the regulation doesn't require the label to separately disclose every solvent, carrier, or preservative used to stabilize that extract. It's not necessarily hiding anything alarming. It's just a label that, by design, tells you less than it looks like it does.
Instant coffee has its own acrylamide gap
Hong Kong's Consumer Council tested 49 coffee products in January 2022 — 10 whole beans, 9 capsules, 16 ground powders, and 14 instant coffees — and detected acrylamide in 47 of them. Instant coffee was the worst category by a wide margin: levels ranged from 160 to 790 micrograms per kilogram, versus 53 to 240 µg/kg for every other format tested. The highest single result belonged to Nestlé Taster's Choice Original Soluble Coffee, at 790 µg/kg.
Every sample still came in under the EU's benchmark levels (400 µg/kg for roasted coffee, 850 µg/kg for instant) — so nothing tested was "illegal" anywhere. But acrylamide is a genotoxic carcinogen with no known safe threshold, and a 5x spread between the cleanest and dirtiest instant coffee on the same shelf tells you the gap is about process, not physics. Some manufacturers are already doing better; the products just don't say which.
Ochratoxin A: the mold toxin the US doesn't limit in coffee
Coffee beans can carry ochratoxin A (OTA), a toxin produced by mold that grows during storage and processing, particularly in humid conditions. A 2024 systematic review in Food Additives & Contaminants: Part A pooled 3,256 coffee samples from studies published between 1997 and 2024 and found OTA in 54.6% of them (1,778 samples), with detection rates ranging from 7.5% to 100% depending on the study and region.
Here's the regulatory gap: the EU sets hard maximum limits for OTA in coffee — 3 µg/kg for roasted coffee and 5 µg/kg for instant coffee, tightened as of Commission Regulation (EU) 2022/1370. The United States has no equivalent limit for coffee specifically. The FDA can still act against a product as "adulterated" case by case, but there's no published numeric ceiling a US coffee brand has to test against — which means a coffee that would fail in France can legally sit on a shelf in Ohio.
What to actually do with this
None of this means coffee is uniquely toxic — trace heavy metals are in a lot of plant-based foods, and most of what Clean Label Project found stayed under EU thresholds. But two things in this data are genuinely actionable: additives that are a formulation choice, not a soil condition (carrageenan, "natural flavors," potassium phosphate), and a US regulatory gap (no ochratoxin A limit, non-binding acrylamide guidance) that means the label alone won't tell you which coffee is the cleaner one on the shelf.
That's the gap Tallow is built to close. Scan a bottled or canned coffee before it goes in your cart and Tallow flags whether it's carrying carrageenan, seed oils, or other stabilizers, scores it on ultra-processing, and tells you what's actually different between two nearly-identical bottles. We've already scored dozens of coffee products — Starbucks, Dunkin', Nescafé, Lavazza, and more — on Tallow's coffee category page, so you can compare before you buy instead of decoding an ingredient panel in the checkout line.