Opinion ID: 1176318
Heading Depth: 2
Heading Rank: 6

Heading: Equilibrium Factors

Text: As we discussed in part IV, the translation of a radon-222 concentration into working levels requires the application of an equilibrium factor. Using equilibrium factors reported in the scientific literature, EFSC chose an equilibrium factor of 0.4 for indoor air and 0.45 for outdoor air. Petitioners' expert testified that his review of the scientific literature showed that an equilibrium factor of 0.4 to 0.5 was reasonable. The expert contended, however, that equilibrium factors were difficult to estimate and that it would be more protective of public health to assume an equilibrium factor of 1.0, i.e., to assume perfect equilibrium between radon-222 and its daughters. EFSC could, upon this evidence, reasonably have found that 0.4 and 0.45 were the appropriate equilibrium factors. We have discussed above petitioners' arguments concerning the health consequences of using working levels as a measure of radioactivity.