A COMPARISON OF GEOLOGY TO RADON TEST DATA IN PORTLAND, OREGON

In recent research, radon has been identified as the second leading cause of lung cancer. Radon gas exists naturally at low levels; it is when the gas becomes concentrated in living spaces that a health hazard arises. Radon distribution in the Portland area was last performed in 2003 for long-term test data. The intent of this examination is to provide an update to the 2003 data and for the first time examine short-term testing data. The raw data was limited to tests performed in living areas only, and the highest reading for a given address. Radon distribution is based on zip code geographical boundaries. This examination adds 65 zip codes to the 2003 dataset. Each zip code was examined for maximum radon reading, average radon reading, and percent greater than 4 pCi/L. These four values combined determine the radon potential for each zip code. Based on the long-term data, nearly 90% of homes in the Portland area have moderate to high radon potential. The short-term data indicates that nearly 98% of homes are within these ranges. There is some variation in the distribution of radon levels within the Portland metro area and one of the reasons for this is that zip codes cut across geologic boundaries. Geologic examination shows that the moderate and high potential areas are associated with porous Missoula Flood deposits or landslide deposits that allow for easier release of radon gas. Radon hazard potential can be better understood with an examination of the underlying geology.