[ahupp]

nit, but this is usually accomplished with plasma donation (plasmapheresis) rather than blood donation. You can donate plasma much more frequently (2x/week) vs blood (once per 2 months), thought the volume taken for each is roughly similar.

[b112]

The filters used must be a specific size, so how micro, are micro plastics? If they keep breaking into smaller pieces, wouldn't they be cell sized too? And thus, pass cell sized filters?

[ahupp]

They don't filter the plasma, they remove it and replace with some other substance depending in your condition and risk profile.

[b112]

You have to filter whole blood, to get plasma.

[ahupp]

So you filter out the blood cells (45% of volume), toss the plasma (55% of volume) and return blood cells + clean plasma. Any substances the plasma are gone. So this is useful to the extent that the substances you care about are free in plasma. At least in the case of PFAS ("forever chemicals") that seems to be the case, see "Effect of Plasma and Blood Donations on Levels of Perfluoroalkyl and Polyfluoroalkyl Substances in Firefighters in Australia", which found that 52 weeks of plasma donation reduced PFAS blood levels by ~30%. This was more effective than blood donation, which reduced levels by 10% and 0% depending on the specific substances you look at.

https://jamanetwork.com/journals/jamanetworkopen/fullarticle...

[b112]

If there are microplastics the size of blood cells (this is a range, as cells are differing sizes), how do you filter for blood cells only?

You can dual filter, smaller and larger than, but you'd still have plastics.

[ahupp]

Ah, I see, sorry for missing your point. In the paper they injected particles of size "9.55 µm, 1.14 µm, 0.293 µm", and it looks like a red blood cell is 8um. So a purely mechanical filter that got red blood cells would retain the largest of those particles but potentially not the rest. But plasmapheresis uses a combination of centrifugal separation and filters so may be more or less effective than that depending on the properties of the cells and plastics.