Radon Decay Products are measured in Working Level (WL) units. Since the primary health effects of radon are due to radon decay products (RDPs) and not the radon-222 gas itself, a unique unit of measure for quantifying the amount of RDPs in the air had to be established. This unit of measure is the working level (WL) and was previously used to measure the occupational exposure of underground miners. A working level is defined as any atmospheric combination of the short-lived radon progeny [polonium-218 (Po-218), lead-214 (Pb-214), bismuth-214 (Bi-214), and polonium-214 (Po-214)] that will deliver 1.3 x 10 to the fifth power million electron volts (MeV) of alpha energy per liter of air. The risk of adverse health effects increases as the WL increases.
|– 1 WL = 100 pCi/L |
– But only in a perfect environment because…
– ER will affect the ratio of WL/pCi/L by approximately 50%.
– Mathematically, this would change the 1:100 ratio to 1:200.
– See Formulas and Chapter 5!
However, measuring radon is a complex system affected by many environmental factors, such as plate-out, the process whereby small RDP particles attach to walls, carpets, furniture, lung tissue, and so forth. Since RDPs are chemically reactive (i.e. have static electric charges) they easily attach themselves to breathable particulate matter in the air (e.g., dust, smoke and aerosols) and subsequently deposit, or plate-out, on solid objects such as walls, floors, ceilings, furniture and clothing, reducing their airborne concentrations.