Plastic in the blood?

he headline seemed nuts: Scientists find microplastics in blood for first time. The image associated with the article shows mm-size bits--which is even crazier. Never mind the picture--how do you get bits of plastic into the blood? My intuition says this is hard--otherwise we'd have all sorts of stuff getting into the blood.

The actual report is at Science Direct. It starts out talking about particle sizes, which explains why the summarizer at phys.org thought of larger bits. But read on.

When you get down to the Methods section, it looks a little different. They describe careful methods to avoid contamination, how they tried to denature and digest the proteins, and then filter the resulting blood samples on a 25nm glass fiber filter (mesh size 700nm).

The next steps had to do with baking the result and testing for chemicals baked out.

The compounds that are desorbed in the first run (‘shot’) are molecules that are volatilized between 100 and 300 °C and can include unpolymerized monomers, additives and other sorbed chemicals. Polymerized target analytes such as polystyrene, EPS, ABS, PP, PE, PMMA are physically unable to volatilize in the ‘first shot’ because the maximum temperature of 300 °C is too low (therefore they are retained for the second shot).

Why the distinction? Because you could have chemicals from your body's trying to digest plastic in your blood, or from inhaling gases from soft plastics, and so on. These are presumably not good, though whether they are actively bad isn't quite proven.

They find chemicals at the right point in the procedure to have been driven off of small particles, but they don't know the size, or if these are new combinations of polymer chemicals and something else. They don't actually see the particles.

And...

The human placenta has been shown to be permeable to 50, 80 and 240 nm polystyrene beads (Wick et al. 2010) and likely also to microsized polypropylene (Ragusa et al. 2021). In a study of acute lung exposure to nanopolystyrene spheres (20 nm) in rats, the translocation of plastic particles to placental and fetal tissues was demonstrated (Fournier et al. 2020). Bioaccumulation of small polystyrene micro-particles in the liver, kidney and gut was observed after oral administration in mice in vivo

And they mention drug delivery in nano-sized plastic particles--and reference something odd in which chronic exposure to "polymeric nanoparticles" in the blood results in clearing the particles out more quickly.

How does this stuff get in? "Mucosal contact"--skin is pretty protective. Really fine stuff (<.1micrometers) can be inhaled. Plus "PE in toothpaste, PET in lip gloss, dental polymers": "even tattoo ink residues."

My intuition was wrong. Partly. The bits have to be very small.