You'll be surprised what it picks up over time, and consequently what you end up not inhaling...
My understanding is that the health benefits are most pronounced from avoiding smoke and fine dust particles which don't necessarily have a lot to do with plastic, but it's a good recommendation regardless.
There is significant evidence linking PM2.5 concentrations and health (which is a common metric about fine particles in the air of a particular size, in this case 2.5 micron range)
They are so effective that they will literally filter a bad smell out of a room assuming it’s not a gas that’s making then smell.