Absorption, distribution, and elimination of [14C] polyethylene terephthalate microplastics in lactating sheep upon oral administration

Authors: Shelver, Weilin; McGarvey, Amy; Billey, Lloyd; Singh, Anuradha

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Microplastics/nanoplastics (MP/NP) are environmental contaminants that have been increasingly found in feed, food, and water used for human and/or animal consumption. Polyethylene terephthalate (PET) is one of the major plastics produced to make single-use beverage bottles, clothing, carpets, and packaging materials. Because of the weathering process, PET MP/NP have become one of the major MP/NP contaminants found in different matrices. Only limited information is available on the fate of MP/NP in domestic food animals. In this study, sheep were dosed with PET NP labeled with a radiotracer and the distribution of NP was monitored. Low but measurable quantities of the PET NP were found in blood, milk, and urine throughout the 24 and 72-hours withdrawal periods. The vast majority of the NP was excreted in feces. These results suggest that PET NP are poorly absorbed by ruminants and that the majority of the ingested NP return to the environment through fecal excretion and edible products would be low in NP concentration.

Technical Abstract: Polyethylene terephthalate (PET) is the most common plastic that is widely used in packaging, fabrics, electronic, and textile industries. Through weathering and degradation, PET becomes one of the most frequently detected microplastics/nanoplastics (MP/NP) in food and the environment. Reports describing the absorption, distribution, and excretion of MP/NP in terrestrial food animals are limited. In this study, lactating sheep were orally administered a single dose of 2.67 ± 0.19 mg/kg body weight [14C] PET NP (230 - 510 nm; 980 µCi, n = 6). Three sheep were sacrificed 24- or 72-hour post dosing and radioactivities in feces, milk, urine, and tissues were measured. Plasma contained low but quantifiable [14C] PET NP from 2 hours post dosing until slaughter and had a long elimination half-life of ~ 80 hours. Total radioactive recoveries in milk and urine were < 0.02% and < 0.3%, respectively. Radioactivities were present in the mammary gland tissue (< 0.01% recovery) of sheep at 24-hour withdrawal, but not at 72-hour withdrawal. Quantifiable [14C] activities were present in some of the gastrointestinal tissues including abomasum, cecum, colon, omasum, and rumen in animals harvested 24 hours post dosing (< 0.6 % recovery). However, [14C] PET NP residues were not quantifiable in skeletal muscle, liver, lung, or kidney. The majority of the [14C] activity was detected in feces (~ 75% at 24-hour withdrawal & ~ 99% at 72-hour withdrawal). These data suggest that most dietary [14C] PET NP would recirculate in the environment through fecal elimination.