Microplastics Found in the Blood of Every Dog and Cat Tested in New Study

In a finding that is likely to make pet owners everywhere pause, researchers in Italy have detected microplastic particles in the blood of every single dog and cat they examined. The study, published in the journal Environmental Advances, is the first to document plastic particles circulating in the bloodstream of living companion animals under ordinary, real-world exposure conditions. All 20 animals tested — 14 dogs and 6 cats — carried microplastics in their blood, a detection rate of 100 percent that surprised even the research team.

The animals involved were not laboratory subjects. They were ordinary pets visiting a veterinary clinic for routine check-ups or scheduled surgeries, with no known metabolic diseases. Blood drawn for clinical purposes, which would otherwise have been discarded, was instead frozen and analyzed after the owners signed informed consent. No procedures were performed on the animals for the sake of the research, an ethical design that reflects a growing effort to study environmental contamination without adding to animal burden. The pets ranged widely in age, with mean ages of about 7.3 years for dogs and 7.15 years for cats.

Isolating plastic from something as complex as whole blood demands a carefully validated protocol. The researchers transferred two-milliliter blood samples into pre-cleaned glass containers and digested the organic material using a Tris-HCl buffer and hydrogen peroxide, incubating the mixtures for 48 hours at 37 degrees Celsius on an orbital shaker. The resulting solution was vacuum-filtered through PTFE membranes with five-micrometer pores, followed by a second oxidative treatment directly on the filter to remove any residual biological material. Particles retained on the membranes were then sorted under a stereomicroscope based on shape, color, and size, and confirmed with the hot needle test, a simple but effective qualitative check in which a heated needle causes genuine plastic particles to melt or curl.

Contamination control was central to the study’s credibility, since airborne fibres are a notorious source of false positives in microplastic research. All sample processing took place inside a clean air flow cabinet, and every piece of equipment was rigorously cleaned with filtered deionized water. Two types of blanks were run alongside the samples: an airborne blank consisting of clean membrane filters exposed to laboratory air, and a full procedural blank containing all reagents but no blood. Neither blank yielded a single particle, giving the team confidence that the plastics they found came from the animals themselves rather than the laboratory environment.

In total, the researchers counted 127 particles across the 20 samples, ranging from 2 to 13 particles per animal, or roughly 1 to 6.5 particles per milliliter of blood. Cats showed a slightly higher mean particle count than dogs, but the difference was not statistically significant. Fibres dominated over fragments in both species, making up about 56 percent of particles in dogs and 64 percent in cats, and black was by far the most common color across both morphotypes. Statistical comparisons using Welch’s t-test, chi-square tests, and a two-way factorial ANOVA on log-transformed length data found no significant differences between dogs and cats in abundance, morphology, color distribution, or particle size — a pattern that hints at shared exposure pathways.

To identify the chemical identity of the plastics, the team used Raman spectroscopy, a technique that fires a green 532-nanometer laser at individual particles and reads back a molecular fingerprint unique to each polymer. A randomly selected 20 percent subset of particles was characterized this way, revealing polyethylene and polypropylene as the dominant polymers, along with cellulose acetate and a polyethylene-polypropylene copolymer. Polyethylene and polypropylene are the two most widely produced plastics on Earth, found in packaging, textiles, bottles, and countless household items. Cellulose acetate, notably, is the primary material in cigarette filters, and its presence in the blood of these pets may reflect urban environmental exposure to tobacco-derived debris.

The size distribution of the particles raises some of the most intriguing scientific questions. Most particles fell within the low micrometric range, the size class generally considered most capable of crossing gastrointestinal and respiratory epithelia through paracellular, transcellular, or immune-mediated routes. But the team also recovered larger fragments, including a cellulose acetate particle measuring 74 micrometers — far wider than the 5-to-8-micrometer diameter of mammalian capillaries. Recent human blood studies have reported similar puzzles, with one finding mean particle lengths of approximately 128 micrometers and a maximum of 3,000 micrometers. How such oversized particles navigate the circulatory system remains unclear.

Several hypotheses could explain the paradox. Larger particles might enter the bloodstream through localized disruptions of epithelial barriers or through transient increases in permeability. Specialized M-cells in the gut’s Peyer’s patches are known to sample and transport particulate matter, and inhalation followed by translocation across the alveolar epithelium is a plausible route, particularly for elongated, flexible fibres. Particle shape itself may matter: unlike the rigid spherical beads used in many toxicology experiments, irregular fibres and fragments may possess the deformability to squeeze through narrow microvascular beds, much as red blood cells do. Alternatively, larger particles found in blood may simply be in transit through larger vessels before being filtered out or sequestered by the immune system. The authors caution that with a small, exploratory dataset, these interpretations must remain provisional.

The findings place companion animals squarely within the One Health framework, the recognition that human, animal, and environmental health are inseparably linked. Pets share our homes, our air, and largely our lifestyles, making them excellent sentinels for contamination that humans also experience. Previous work has found suspected microplastics in the lungs, liver, kidney, intestine, and blood clots of deceased dogs and cats, in canine testicular tissue, and even in feline placentas and fetuses, demonstrating that these particles can breach the placental barrier and reach developing organisms. The new study extends this picture to the living bloodstream, the compartment through which any multi-organ distribution must pass.

Perhaps the most consequential implication concerns exposure routes. Earlier research showed that concentrations of polyethylene terephthalate in pet feces were one to two orders of magnitude higher than in the pet food the animals consumed, suggesting that diet alone cannot account for the plastic burden. Indoor air and household dust, laden with synthetic microfibres shed from textiles, have emerged as likely major contributors — a conclusion reinforced by the fibre-dominated profile seen in the pets’ blood and by human studies pointing to inhalation as a significant route of systemic uptake. For anyone who has ever watched a cat groom itself or a dog chew a plastic toy, the picture is now more complete: microplastics are not just in our pets’ environment, but circulating within them. The authors emphasize that animal models have linked microplastic exposure to oxidative stress, inflammation, endocrine disruption, and reproductive toxicity, though no clinical correlations were examined here. Their preliminary data, they hope, will pave the way for larger, more balanced cohorts and mechanistic studies that can finally define what this invisible circulation means for the health of the animals that share our lives.

Subject of Research: Detection and characterization of microplastics in the blood of living dogs and cats

Article Title: Presence and characterization of microplastics in pet blood (dogs and cats): evidence of environmental contamination

Article References: Cerquetella, M., Cocci, P., Marchegiani, A., Gabrielli, S., Minicucci, M., Gregori, M., Zamporlini, C., & Palermo, F. A. (2026). Presence and characterization of microplastics in pet blood (dogs and cats): evidence of environmental contamination. Environmental Advances, Article 100767. https://doi.org/10.1016/j.envadv.2026.100767

Image Credits: AI Generated

DOI: 10.1016/j.envadv.2026.100767

Keywords: microplastics, dogs, cats, blood, Raman spectroscopy, polyethylene, polypropylene, One Health, environmental contamination, companion animals, indoor dust, veterinary toxicology