Fiberglass appearing in home dust
Many of have worked in attics without masks over the years at hundreds or thousands of times the exposure you are getting but I won’t say it’s not a health issue but I am not aware of any issues with such a light exposure. 

Other areas to check include the duct work. Metal trunk ducts usually have a fiberglass blanket that is foil backed. If someone tweaked the trunk line they may have disturbed a seam and created a Venturi that is pulling some fibers in, I bring this up because a home owner sat on his trunk line and it pulled in quite a bit but I was able to seal it up, since the ceiling was down you may have not noticed. 

Flex duct (usually black plastic inside and outside with insulation in the center) could have pulled loose and exposed the fiberglass on the inner plastic a flashlight would show yellow or pink fiberglass if this happened. Other than that sealing the fixtures would be the areas to look at if it’s not showing up in other rooms of the house. As I said I am not aware of any issues with such low levels but there may be a stuffy out there that says it is dangerous, asbestos was once thought to be safe along with the Hindenburg.