I think the author's mental model of what makes particulates dangerous is odd.
In part 1 of the post he mentions the molecular size of PFAs, and in part 2 he mentions benzene. I think "size" is not the relevant property - it's "does this molecule get imported into cells and alter some component of their activity". While molecular size is related to this, it's more about presence of transporters on the cells, hydrophobicity of the molecules, how the liver handles them (e.g. phase I/II metabolism) etc.
You can contrast this with asbestos, which is dangerous because it mechanically disrupts mucus clearance in the lungs without being imported into cells (also why asbestos + smoke is very dangerous, but asbestos alone probably not nearly as problematic).
Microplastics increase the surface area for degradation in the body, and thus might increase intestinal (and then blood) concentrations of plastic component chemicals or heavy metals they complex with. However, I think it's mainly a phenomenon of degradation in the intestine and then import into the blood stream. Contrast this with "microplastics get into the bloodstream intact". While there might be some of that going on (e.g. phagocytosis by macrophages, eosinophils, etc) I think it's the wrong mental model.
As a bit of reference, remember that your large intestine contains about 1E13 microbes/gram of digesta, and they are 0.2-2um in size. If the intestine let things of that size in at high rate we'd all have sepsis all the time
You are right - I am building a mental model along these lines:
a) compounds which induce a chemical reaction inside cells and as a result cause damage. Benzene, PFAS, phtalates, BPA etc are in this category. Size is less relevant but usually these are smaller and more reactive molecules.
b) small particulates, which are still probably much larger than those in group a). Thinking here microplastics, asbestos, PM10. These particulates are not necessarily super reactive with our cells, but they can cause problems through physical accumulation(?). So the question is: does the size of microplastic particles matter? Ie if I get 1K of 100 micron microplastic particles vs. 1K of 1 micron - does that alter my health risk?
In part 1 of the post he mentions the molecular size of PFAs, and in part 2 he mentions benzene. I think "size" is not the relevant property - it's "does this molecule get imported into cells and alter some component of their activity". While molecular size is related to this, it's more about presence of transporters on the cells, hydrophobicity of the molecules, how the liver handles them (e.g. phase I/II metabolism) etc.
You can contrast this with asbestos, which is dangerous because it mechanically disrupts mucus clearance in the lungs without being imported into cells (also why asbestos + smoke is very dangerous, but asbestos alone probably not nearly as problematic).
Microplastics increase the surface area for degradation in the body, and thus might increase intestinal (and then blood) concentrations of plastic component chemicals or heavy metals they complex with. However, I think it's mainly a phenomenon of degradation in the intestine and then import into the blood stream. Contrast this with "microplastics get into the bloodstream intact". While there might be some of that going on (e.g. phagocytosis by macrophages, eosinophils, etc) I think it's the wrong mental model.
As a bit of reference, remember that your large intestine contains about 1E13 microbes/gram of digesta, and they are 0.2-2um in size. If the intestine let things of that size in at high rate we'd all have sepsis all the time