Threats to health can be scary. But in this case, you'll want to keep on learning about radon. Learn what it is, exactly; learn where it's found in terms of what part of the building, and how it's mitigated.
The upshot is I've never heard of a radon mitigation system on the second floor, least of all the 9th! You have more to fear from wildfire.
Radon is emitted only from rocks in the ground or from masonry. Unless your apartment is composed entirely of raw concrete and has no ventilation, radon is an unlikely concern. You can buy small testing kits that will tell you how much radon is present.
On another note, it also debatable what concentration of radon is linked to an increase in cancer. ...