• Natural soils and rock near or beneath building.
  
  Granites, shales, and corals, etc. can have slightly elevated levels of uranium (approx. 5 pCi/g)
  
  
• Contaminated soils from uranium processing mills, and contaminated building materials.
  
  This is relatively rare and well known in local areas.
  
  
• Groundwater supplies directly from wells.

Some antique dishware and clock collections have been painted with radium based paint. When doing a building investigation these items should be noted if they are present.

Factors Influencing Radon Source Potential

• Radium content
  
  
• Size of particles: the smaller the particles the more surface area
  
  
• Porosity of soil: the ease of soil gas movement into a building
  
  
• Forces pulling or pushing soil gas through soil

Some or all these factors play a part in soil gas radon concentrations. This explains the extreme variations that have been observed in soil gas measurements, ranging from about 100 pCi/L to 100,000 pCi/L. Because of these variations, taking soil gas radon measurements before construction will not give us an indication as to what the radon concentrations will be after construction.

Copyright 2000, Great Lakes Center for Occupational & Environmental Safety & Health, School of Public Health, University of Illinois at Chicago