From Ann Barnhardt site:

"When polypropylene is inhaled in factories where it is manufactured, that is
in factories in which workers are likely to inhale polypropylene fibers, it has
the potential to result in an increased risk of a type of interstitial lung disease
called Flock Worker’s Lung, named so because of the lung disease found in
flocking plants. Atis et al studied workers employed in a flocking plant that
used polypropylene (Eur. Respir J, 2005). They noted: “logistic regression
analysis showed that the risk of respiratory symptoms increased 3.6-fold in
polypropylene flocking workers when compared to controls…” they also
measured CT scans in patients (which will show evidence of lung damage
from interstitial lung disease) and noted that “high resolution CT scan in a
limited number of subjects, are indicative of the beginning of or mild
interstitial lung disease…” They also noted a significant decrease in carbon
monoxide diffusing capacity in exposed workers vs controls, namely a 10
point reduction from 85.6 to 75.8) which was highly significant (p=0.001). A
decrease in diffusing capacity is a hallmark for lung damage, especially from
interstitial lung disease. So, is it possible that prolonged use of facial masks
or N-95 respirators, which contain polypropylene may increase the risk of
long-term interstitial lung disease when one inhales the frayed fibers? To
date, no one has raised the question."

PDF
https://christinajones1.wixsite.com/website/post/what-s-behind-the-mask

Don't know about that but one risk already proven is the chance of catching Legionnaires from long term wearing

Could you tell us where you learned about the Legionnaires connection?

All my life, all I ever wanted to do was sell polypropylene!  All my aunts, uncles, cousins, grandparents, parents, and neighbors are In polypropylene!  What are we to do now?

Maybe you can try polystyrene or polyethel-ine or poly-Mabel-ine or just plain Abilene 

Perhaps you missed the point.  Most of those cheap blue disposable masks people are wearing contain polypropylene, and polypropylene has been linked to lung disease.

Methinks Sean’s post must be read with Monty Python glasses. Unless I am off base, at which point call the witch doctor.

Not only that, they spray them with formaldehyde in the factory, and people are having facial reactions/breakouts.  

Lovely!  Sign me up!