 Under these conditions, each additional pCi/L of radon will increase exposure by 0.01 "working level" (WL, a measure of radioactivity commonly used in mining).These conditions are not always met; in many homes, the equilibrium factor is typically 40%; that is, there will be 0.004 WL of daughters for each pCi/L of radon in the air.210Pb takes much longer (decades) to come in equilibrium with radon, but, if the environment permits accumulation of dust over extended periods of time, 210Pb and its decay products may contribute to overall radiation levels as well.