Do I need to worry about Radon gas if my home is on a slab or crawlspace?

Yes.

Since Radon comes from our soil, it breaches the home through your crawlspace floor drain, sump pit, foundation cracks, sinks, showers, and all other building envelope penetrations. n

The amount of radon that escapes from the soil and enters the house depends on the weather, soil porosity, soil moisture, and suction within the house.