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Most of Oregon has been mapped as having low radon potential. Overall, elevated levels of indoor radon are found in only 4% of Oregon homes compared to 8% of homes nationally. Most maps show Portland, Oregon’s largest city, as having low to moderate potential for indoor radon. Using data collected by the Oregon Health Division’s Radiation Protection Services Section, we found Portland to have elevated radon values in 22% of homes. A radon potential map has been produced for 39 zip code regions of Portland based on the rank sums of maximum radon values, average indoor radon values, and the percentage of homes with radon values >4 pCi/1. Eight zip codes have high, 15 moderate, and 16 low radon potential. The maps were constructed by taking the indoor radon values from 1,135 homes, categorizing the data in terms of radon values, and plotting the points geographically by zip codes. Trends became obvious when geologic maps were compared to the areas of radon potential. Most of the high potential sites lie on highly permeable Missoula flood sediments. The data and map of radon potential were presented to the public through television and radio interviews and newspaper articles in June of 1994. The public, already familiar with the zip codes, could understand how to use the map. People in high to moderate categories were strongly encouraged to test their homes. A telephone number was given to receive free information on radon testing and mitigation.

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