Radon is produced underground by granite bedrock and possibly in lesser amounts by other types of bedrock. The radon migrates through subsurface groundwater, rock and soil and into basements through cracks, seams, sump pumps and concrete/block pores. The radon gas decays into daughter dust products such as lead and polonium that can be inhaled. The decay of these radioactive byproducts release ionizing radiation, which can cause lung cancer.
The highest range of radon risk in southeast Michigan generally correlates with an arc-shaped geologic formation (light green) extending from Port Huron and continuing west to southwest through Romeo, north Pontiac, Novi, Brighton, Ann Arbor and continuing down through the Hillsdale region. However, the unpredictable combination of various subsurface factors and building conditions can result in elevated levels of Radon anywhere in Michigan.
adapted frrom the MDNR Bedrock Geology Map of Michigan, 2001
According to American Lung Association data, the following is an example of the radon test fail rates for selected municipalities:
The following areas were ranked by the American Lung Association as the top radon hazard locations (with a sufficient testing sample size):
3. Whitmore Lake
4. South Lyon
5. Washington Township/Romeo
6. Milford/New Hudson
10. Bloomfield Township
There is a secondary corridor of elevated radon risk located in the Downriver area :
Based on my own testing experience, 6% of homes tested in the Detroit area that were installed with a passive radon ventilation system failed the initial screening test for validating performance of venting system.
Typically a 48-96 hour screening test is conducted in the center of the basement. The accuracy of this test is believed to be approximately +/- 50%. Based on the results of this test, a longer duration and more accurate test may be required. Radon screening costs range from $50 to $200 depending on the purpose of the test (unofficial results vs. official results for a real estate transaction).