RADoN Physiology and the Home

Radon Physics and Physiology

Radon Entry into the Home

Text Box: Uranium-235 decays into a series of elements to ultimately produce Radon-222. Radon is a gas which has a half life of 3.8 days. This means that within 3.8 days half of the Radon will decay to a lower atomic weight element. It is when the elements decay that the danger occurs. Each decay is marked with the release of an Alpha particle which consists of 2 Neutrons and 2 Protons. They initially travel at about 1/2 the speed of light or 93,000 miles/sec. Though they are small, their speed causes them to do great damage when impacting the DNA in a cell. They also have a great risk of striking and knocking off electrons called Beta particles from other atoms which turns these atoms into ions. These ions will also cause damage to body tissue. The third release that occurs with the decay of these elements is pure energy - Gama radiation—which is similarly harmful.
Just as Alpha and Beta particles and Gama radiation are released when Radon decays they are also released as the decay products themselves decay. As a gas, Radon is breathed in and then out. The decay products are solids however and they will plate or attach to the lining of the lung and stay there for a period of time. The Decay products have a much shorter half life and have a greater chance of decaying while on the lining of the lung making their risk much greater than the Radon itself.
As you can see from the above the goal is to reduce or minimize the amount of Radon entering the home and living space and rapidly remove decay products when possible. We deal effectively with both of these in our mitigation strategies.

The decay of Uranium-235 occurs many hundreds of miles deep in the earth. Since the Radon is the first gas in the string of decay it is free to move toward the surface, forced up by the pressure of the molten solids. As it reaches the solid crust it finds cracks which allow it to escape into the atmosphere. Once in the atmosphere it is diluted with other atmospheric gasses to a safer level.
If, however the channel brings the gas to a point below your home, the gas will be pulled into your home by a mild vacuum which occurs in all homes. 
It is common knowledge that heat rises. The home works with this principal and as the warm air within the home moves up (stack effect) and out of the upper levels of the home it will produce a slight vacuum. Additionally, bathroom and kitchen exhausts, clothes dryer vents and other components will increase this vacuum. Radon is pushed up into this vacuum from atmospheric pressure pressing down on the soil and other sources of pressure such as wind pushing against a hill and water draining into the soil forcing gasses up and out of the soil. Though it is a good idea to caulk and seal leaks cracks in basement floors and joints where the concrete meets walls etc. Radon will find a new way to seep into the living space.
The level of Radon entry is not the fault of building design though Radon resistant construction can reduce the risk. It is more the channels arriving under the basement floor. Much like a guesser basin, if your home is built on Old Faithful you will be very wet. Most homes in our area are built more on the mud pot level (Yellowstone analogy). Though you won’t get soaked you will often find your feed wet. 

Radon levels are measured in pCi/l (pica Curie per liter). A Curie, named after the famous scientist, is the amount of radiation given off by a gram of uranium.  pCi/l is the amount of radiation give off from a liter of gas or liquid. Radon can be found in air or water and both can be accurately measured. 
The only safe level of Radon is no Radon. Though this is not possible we strive to approach it. The EPA arbitrarily sets 4.0 pCi/l as a target maximum where the World Health Organization recently lowered their target maximum to 2.6 pCi/l.  Ambient outside levels in the US are around .4 pCi/l and in homes the national average is 1.4  pCi/l. In our area the level averages 4.6 pCi/l in homes. We live in a high radon area.
Since Radon is both colorless, tasteless and odorless the only way to know your level is to test your home. Test kits and electronic measurements are available from us. They are also available from local health departments for free or a small fee. All homes in our area (Southern Wisconsin) should be tested and repaired to minimize the risk. 
Text Box: Home Entry
Text Box: Radon Measurement