Microplastics have turned up in yet another staple of the global diet, and this time the evidence comes with unusually rigorous analytical backup. Researchers at the University of Tabriz examined 30 commercially available milk samples purchased from supermarkets in Tehran, Iran, and found potential microplastic particles in every single one. Concentrations ranged from 5 to 36 particles per liter, with a mean of 18.4 particles per liter. The finding, published in Current Research in Food Science, adds milk, a food consumed daily by billions of people, to the growing list of everyday products carrying microscopic plastic debris, and it points an intriguing finger at one particular part of the dairy supply chain: the bottle.
The study, led by Nazanin Jabbarzadeh and colleagues, stands out in a crowded field for the care it took with quality control. Microplastic research has been criticized for inconsistent methods, missing blanks, and questionable identifications, so the team built their workflow around safeguards. They processed five procedural blanks per batch, exposed blank filters to laboratory air during each filtration session, pre-filtered all reagents through 0.45 micrometer membranes, and wore cotton lab coats and nitrile gloves inside a laminar flow hood to minimize airborne contamination. Procedural blanks averaged just 1.2 particles per filter and airborne blanks 0.6, yielding a detection threshold of 3.6 particles per filter, well below the lowest sample concentration recorded.
Each one-liter milk sample was digested with 30 percent hydrogen peroxide at 60 degrees Celsius for 24 hours, then vacuum-filtered through 1.2 micrometer glass fiber filters. To gauge how much material the method might lose along the way, the researchers ran spike experiments, adding known quantities of standard microplastic particles to ultrapure water and processing them exactly like samples. Recovery rates ranged from 82 percent for polyethylene terephthalate to 96 percent for polyethylene, with an overall mean of 89 percent. The team then corrected reported concentrations using these polymer-specific recovery factors. They are careful to note, however, that because the spikes were performed in water rather than milk, the recovery figures do not amount to a complete matrix-matched validation of the method for the dairy matrix itself.
Microscopic screening under a stereo microscope at 40 and 100 times magnification recorded 551 particles across all 30 samples. Morphologically, the haul was dominated by fragments, which made up 58 percent of the total, followed by fibers at 35 percent and spheres at 7 percent. Fibers were mostly blue or transparent, while fragments displayed a broader palette including black and red. Three trained analysts counted particles independently for each filter, with the mean recorded to limit observer bias, and systematic grid patterns prevented double-counting. Critically, the authors treat visual examination as a screening step only, not as definitive evidence of polymer identity, a distinction that has often been blurred in earlier microplastic studies of food.
To firm up the chemistry, roughly 150 particles, five per sample, were subjected to scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, or SEM-EDS. Gold-palladium sputter-coated particles were imaged at accelerating voltages of 15 kilovolts and magnifications up to 10,000 times, revealing surface textures and elemental fingerprints. A polyethersulfone particle, for instance, showed a telltale sulfur peak in its EDS spectrum, while polyethylene particles were dominated by carbon. But elemental composition alone cannot settle polymer identity, so the particles were then interrogated with micro-Raman spectroscopy using a 785 nanometer laser, with spectra matched against reference libraries and custom standards of seven common polymers.
The Raman analysis succeeded for 142 of the 150 particles, a confirmation rate of 94.7 percent, with hit quality indices averaging 0.92. Polyethylene emerged as the most abundant polymer at 32 percent of identified particles, followed by polypropylene at 24 percent, PET at 15 percent, polyamide at 12 percent, and polyethersulfone at 9 percent, with the remaining 8 percent unidentified or other. That profile is striking because polyethylene and polypropylene are precisely the polymers most common in plastic milk bottles and food-contact materials, while polyamide and PET are characteristic of Tetra Pak laminates. The authors caution, however, that polymer identity alone cannot pinpoint where each particle originated.
The statistical centerpiece of the study is the packaging comparison. Milk sold in plastic bottles contained an average of 24.6 particles per liter, roughly double the 12.2 particles per liter found in Tetra Pak cartons, a difference that was highly significant. In a multiple linear regression model, packaging type was the only meaningful predictor of contamination, explaining nearly half the variance in concentrations, while fat content and brand showed no significant effects. Adding product volume to the comparison erased the statistical difference, and the authors are explicit that the observational design of the study establishes an association with packaging, not proof that bottles are the direct source of the particles.
Perhaps most consequential for exposure assessment is the size distribution. SEM measurements of 350 particles yielded a mean longest dimension of 68.4 micrometers, with a pronounced peak between 20 and 50 micrometers. Fully 72 percent of measured particles were smaller than 100 micrometers, and 41 percent smaller than 50. This matters because smaller particles are considered more capable of crossing biological barriers and being taken up by cells, although the authors stress that their study measured particle characteristics only and did not investigate uptake, tissue distribution, or any toxicological outcomes. No health risk conclusions can be drawn from these data alone, they emphasize, and milk consumption should not be regarded as a demonstrated health hazard on this evidence.
The study also fills a geographic gap. Most foodborne microplastic data come from Europe, the Americas, and East Asia, while regions such as Iran have been thinly covered despite prior reports of microplastics in milk, milk powder, and infant formula elsewhere. The authors call for larger and more geographically diverse sampling, process-line monitoring inside dairies, controlled packaging-release experiments, and matrix-matched validation of analytical methods, alongside standardized protocols that would make cross-study comparisons meaningful. For regulators, the results argue for routine microplastic surveillance in dairy; for producers, for tighter quality control across processing, storage, and filling. For consumers, the takeaway is sobering but measured: microplastics are now documented in commercial milk, plastic packaging shows the strongest association, and the science of what that means for human health remains an open and urgent question.
Subject of Research: Microplastic contamination and polymer identification in commercial milk using SEM-EDS and micro-Raman spectroscopy
Article Title: Microplastic Contamination in Commercial Milk: Quantification and Polymer Identification Using SEM-EDS and Micro-Raman Spectroscopy
Article References: Microplastic Contamination in Commercial Milk: Quantification and Polymer Identification Using SEM-EDS and Micro-Raman Spectroscopy. (n.d.). https://doi.org/10.1016/j.crfs.2026.101571
Image Credits: AI Generated
DOI: 10.1016/j.crfs.2026.101571
Keywords: microplastics, milk, food safety, polymer identification, Raman spectroscopy, SEM-EDS, packaging, plastic bottles, Tetra Pak, dairy products, dietary exposure, Iran
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Daisy Hatcher. (September 20, 2026). Microplastics Found in Every Milk Sample Tested, With Plastic Bottles Worst. Scienmag. https://scienmag.com/microplastics-found-in-every-milk-sample-tested-with-plastic-bottles-worst/
Daisy Hatcher. “Microplastics Found in Every Milk Sample Tested, With Plastic Bottles Worst.” Scienmag, 20 September 2026, https://scienmag.com/microplastics-found-in-every-milk-sample-tested-with-plastic-bottles-worst/. Accessed 20 September 2026.
Daisy Hatcher. “Microplastics Found in Every Milk Sample Tested, With Plastic Bottles Worst.” Scienmag. September 20, 2026. https://scienmag.com/microplastics-found-in-every-milk-sample-tested-with-plastic-bottles-worst/
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