[wnevets]

Which plant produces pollen at PM2.5 tho? Pollen usually isn't entering your bloodstream through your lungs, its too large.

[semi-extrinsic]

Pollen particles are quite fragile and tend to break up into PM2.5 and smaller, especially during rain events. See for instance the reference below.

https://doi.org/10.1016/j.aeaoa.2022.100177

[culi]

In addition to pollen, there are spores from both mushrooms and ferns. Both of which are common cloud-seeding particles and can often be PM2.5