offcamber

I have a 2012 JK Unlimited. I've noticed for the last week or so, little white flakes on the back seat. At first I thought it was something that blew into the window but tonight I had my camera gear in the Jeep after a shoot and noticed when I went to unload tonight there were little white flakes of something all over my camera gear, the top, my bags etc. It looks like it's coming off the hard top. The strange thing is that I've also been coughing a lot when I've had the windows rolled up driving the Jeep in the rain. Anyone else ran into this? Any idea what it is and if it's harmful to breathe?