The EPA estimates that radon[1] is the second leading cause of lung cancer after smoking. I have a RadonEye monitor in the basement. They aren't that expensive and it's nice to have the piece of mind.
Naturally, you would have to account what changes in the sample during shipping, due to the short half-life...
Get a professional measurement and compare. This Reddit thread gave me pause [1].
[1] https://www.reddit.com/r/radon/comments/ptz8tt/professional_...