We get calls asking this all the time. As with any home: the only way to know your radon exposure is to test. Tests are available and affordable
However, I will make some generalizations here for the curious web surfer. Radon is a soil gas. Once it hits our atmosphere it dissipates to–mostly–harmless levels. The risk of radon is having radon decay products accumulate in a confined space. That’s usually the lowest living level of a building. Sometimes it’s a basement, sometimes it’s a first story ranch, sometimes it’s a garage, and sometimes it’s a first-floor apartment. Once inside a building, radon gets spread around by the HVAC system. 
Radon in soil testing is not prevalent because you could build the same home on the same property but use a different heating and cooling system and have two vastly different radon levels. HVAC and pressure dynamics on the building have a very large effect on radon concentrations room-to-room.
I’ve heard anecdotes of radon levels being elevated above 15 stories on sky scrapers before. How, you may ask? Contaminated concrete aggregate. Concrete plants often have no mandates or regulations as it pertains to radon. Radon is extremely prevalent in bedrock and granite. Contaminated concrete or contaminated kitchen countertops (other stories I’ve heard) can be hidden radon sources that often aren’t found until an exasperated homeowner calls the best pro in a 100 mile radius.
So, should you test your apartment? Yes, I think you should. Especially if you live on the ground floor.
