The best replacement for radon is radium.

The best alternatives to radon are rated as following:
★★★★★  radium
★  neon
  carbon monoxide
  krypton
  granite countertops
  asbestos

Your alternative for radon is not listed? Suggest!
Speaking about radon, one probably shouldn't forget about granite.

Other search terms related to radon and their ratings are:
★★★★★ granite
★ mitigation
basements
You have in mind a companion for radon and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of radon in all years. Click on graph for more.
radon
radium
neon