Simplify the following text for a Grade 8 native English-speaking person.
Original: The radon equilibrium factor is the ratio between the activity of all short-period radon progenies ( which are responsible for most of radon 's biological effects ) , and the activity that would be at equilibrium with the radon parent .
Simplified: Radon is radioactive , meaning that it can give off harmful rays . Some people have high levels of radon in their houses , and this can be very dangerous .