Microplastics/nanoplastics (MP) are emerging environmental contaminants of great concern because of their ubiquitous distribution in air, soil, water, and food. Potentially harmful effects of MP on tissues can be through direct interactions or as a vehicle to carry chemical pollutants or pathogens. MP are reported to be present in animal excreta, but their presence in edible portions of terrestrial food animals is essentially unexplored. [14C]-polystyrene MP (10 µCi/hen) were orally administered to 15 laying hens and distribution of radioactivity in blood, 3 largest developing ova, and muscle was determined in hens harvested on withdrawal days (WD) 1, 2, 3, 4, and 7 (3 hens per WD). Eggs were collected on WD1 through WD7 and yolks, whites, and eggshells were separated; radioactivity was quantified in each fraction. Blood from each hen contained measurable [14C] on WD1 and WD2, one out of three hens on WD3 and WD4, and no radioactivity was quantifiable on WD7. The percentage of the administered dose in blood ranged from 0.01% to 0.06% with WD1 having highest average recovery but with wide animal to animal differences within withdrawal day. The percentages of eggs containing measurable radioactivity in egg white were 44%, 100%, 73%, 57%, 0%, 0%, and 25% on WD1 through WD7, respectively, with average amounts of radioactivity peaking on WD2. Percentages of egg yolks containing radioactivity were 13%, 50%, 91%, 100%, 100%, and 75% on WD1 through WD7, respectively; average quantities of radioactivity increased up to WD4 and slowly decreased through WD7. Eggshell contained, on average, 16% of the radioactivity measured in egg white. Of the eggshells collected, 20% contained radiolabeled MP. Recoveries of initial doses across all hens ranged from 0.002 to 0.1% in egg yolk and 0.002 to 0.15% in egg white. Among the 15 dosed animals, one hen had [14C] in breast muscle that was &gt; LOD but &lt; LOQ. This animal also contained the highest cumulative recovery of radiocarbon in eggs (0.27% of dose) when sacrificed on WD4. Average radioactivity in developing ova relative to egg yolk was 6.5x on WD2, 2.0x on WD3, 0.9x on WD4, and 0.2x on WD7. Our data clearly demonstrate that very small amounts of polystyrene MPs were absorbed into blood and was translocated to eggs and muscle.

Distribution of submicron [14C]-polystyrene particles in blood, eggs, and muscle after oral administration to laying hens

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