RADON ON ALAMEDA RIDGE, PORTLAND, OREGON AND THE RELATIONSHIP WITH GEOLOGY

The American Cancer Society has found that radon is the second leading cause of lung cancer, the first leading cause in non smokers. Average, maximum, and percent homes greater than 4 pCi/l was calculated for five ZIP codes: 97211, 97212, 97213, 97218, and 97220. It is hypothesized that the indoor radon readings will be higher in those homes built on the ridge than those built below it, showing a distinct geologic influence on radon. All previous studies done in Oregon focused on whole ZIP codes, not individual house readings. For 719 long term test results, the average value was 4.5 pCi/l, the high was 35 pCi/l, and the percent homes greater than 4 pCi/l (EPA action level) was 46%. The homes on the ridge in this dataset have an average value of 5.3 pCi/l and the percent homes greater than 4 pCi/l was 55%. For the homes at lower elevations, the average value was 4.1 pCi/l and the percent homes greater than 4 pCi/l was 42.1%. For 3958 short term test results, the average value was 6.4 pCi/l, the high was 111.9 pCi/l, and the percent homes greater than 4 pCi/l was 50.4%. For homes on the ridge in this dataset, the average was 8.0 pCi/l and 61% of the homes were above the action level. For homes at the lower elevations, the average was 5.3 pCi/l and 43% of the homes were above the action level. The percent of homes with readings greater than 4 pCi/l are not quite what we expected, but they do illustrate that there is a relationship between higher readings and loosely compacted Missoula Flood sands and gravels, and lower readings and compacted silt/sand Missoula Flood rhythmites. For the winter short term test data, the average was 7.8 pCi/l and percent homes greater than 4 pCi/l is 54.2% while the average for summer short term data was 5.0 pCi/l and percent homes greater than 4 pCi/l is 41.3%. While the difference between winter and summer data is not drastic, it is different enough to show there is a slight relationship with higher readings occurring in the winter when house are closed up, and lower readings occurring in the summer when houses are more open. This study shows that 55 to 60 %, almost 2 in 3 homes built on Alameda Ridge have a reading greater than the EPA action level, compared to 1 in 4 in Portland, 1 in 3 in Oregon, and 1 in 8 in the nation.