I am going to assume it is concrete not cement. Cement should not have been used for anything like that.
Either way, concrete or cement are technically porous. They absorb moisture and release a gas pretty much the whole life of the object. Out here in Arizona most structures in the above ground do not absorb much moisture but foundations and pretty much anything in the ground will. I believe in Maryland, you have a lot higher humidity level than we do. High humidity can cause concrete to be more saturated as well which would cause more of an out gas.
Couple things need to be known.
Is there any seems in the patio? Like the lines every 6' in a sidewalk.
Below the patio, is it open or is it part of the enclosed building?
Has the rooftop been properly sealed?