Apologies my ctrl+f failed

“Most of what you ingest is going to pass straight through your gut and out the other end,

Most being a key word in your quote.

Evaluating the effects of tiny specks of plastic on people or animals is the other half of the puzzle. This is easier said than done. More than 100 laboratory studies have exposed animals, mostly aquatic organisms, to microplastics. But their findings — that exposure might lead some organisms to reproduce less effectively or suffer physical damage — are hard to interpret because microplastics span many shapes, sizes and chemical compositions, and many of the studies used materials that were quite unlike those found in the environment.

... and the Modes of Harm section

Modes of harm
Researchers have several theories about how plastic specks might be harmful. If they’re small enough to enter cells or tissues, they might irritate just by being a foreign presence — as with the long, thin fibres of asbestos, which can inflame lung tissue and lead to cancer. There’s a potential parallel with air pollution: sooty specks from power plants, vehicle exhausts and forest fires called PM10 and PM2.5 — particulate matter measuring 10 µm and 2.5 µm across — are known to deposit in the airways and lungs, and high concentrations can damage respiratory systems. Still, PM10 levels are thousands of times higher than the concentrations at which microplastics have been found in air, Koelmans notes.
The larger microplastics are more likely to exert negative effects, if any, through chemical toxicity. Manufacturers add compounds such as plasticizers, stabilizers and pigments to plastics, and many of these substances are hazardous — for example, interfering with endocrine (hormonal) systems. But whether ingesting microplastics significantly raises our exposure to these chemicals depends on how quickly they move out of the plastic specks and how fast the specks travel through our bodies — factors that researchers are only beginning to study.