Pulmonary fibrosis may be caused by

a.smoking
b.allergic reactions
c.breathing in coal dust.
d.increased mucus production

I'm having trouble with this because doing research I found it to be smoking and breathing in coal dust. So I'm a bit confused.

1 answer

According to this article, cigarette smoking is only a cause in rare instances.

http://www.mayoclinic.com/health/pulmonary-fibrosis/DS00927/DSECTION=causes