General Radon Information

Wisconsin specific radon and radon level information can be found throughout this site. You will be able to find information about certified radon inspectors in Wisconsin, as well as detailed radon level information for every county in Wisconsin.

Radon is a naturally occurring, odorless radioactive gas that causes lung cancer. The World Health Organization, the U.S. EPA and the U.S. Department of Health and Human Services’ National Toxicology Program have all concluded that radon is a known cancer-causing agent in humans. The National Academy of Sciences' Biological Effects of Ionizing Radiation VI Report (1998) concluded that radon causes between 15,000 and 22,000 lung cancer deaths each year in the United States. The U.S. Surgeon General has warned that radon is the second-leading cause of lung cancer in the United States – second only to smoking. For nonsmokers in this country, radon is the No. 1 cause of lung cancer.

Between five and ten percent of the homes in Wisconsin have radon levels above the US EPA guideline of 4 pCi/L for the year average on the main floor. Every region of Wisconsin has some homes with elevated radon levels.

Although no level of radon is considered absolutely safe, the USEPA action level for radon is 4.0 picocuries per liter of air (pCi/L). (pCi/l= picocuries per liter, the most popular method of reporting radon levels. A picoCurie is 0.000,000,000,001 (one-trillionth) of a Curie, an international measurement unit of radioactivity. One pCi/l means that in one liter of air there will be 2.2 radioactive disintegrations each minute. For example, at 4 pCi/l there will be approximately 12,672 radioactive disintegrations in one liter of air, during a 24-hour period.

How does radon enter your home? As air in your house heats up, it rises and leaks out of attic openings and around the upper floor windows, creating a small suction at the lowest level of the house. That suction pulls the radon out of the soil and into your house. Fortunately, there are extremely effective means of keeping radon out of your home. Qualified contractors can typically mitigate radon problems for a cost similar to that for may common home repairs such as painting or having a new water heater installed - anywhere from $800 to $2,500.

Northern Wisconsin, the western part of the Upper Peninsula of Michigan, and part of northern Minnesota are underlain by glacial deposits of the Lake Superior lobe. Parts of northern Minnesota are also underlain by deposits of the Rainy and Wadena lobes. The underlying source rocks for these tills are volcanic rocks, metasedimentary and metavolcanic rocks, and plutonic (granitic) rocks of the Canadian Shield. The volcanic, metasedimentary, and metavolcanic rocks have relatively low uranium contents, and the granitic rocks have variable, mostly moderate to high, uranium contents. The sandy tills derived from these rocks have relatively high permeability, but because of their lower uranium content and lower emanating power, they have mostly moderate to locally high radon potential. Granites and granite gneisses, black slates and graphitic schists, and iron formation are associated with anomalous uranium concentrations and locally high radon in northern Wisconsin and adjacent northwestern Michigan. In central Wisconsin, uraniferous granites of the Wolf River and Wausau plutons are exposed at the surface or covered by a thin layer of glacial deposits and cause some of the highest indoor radon concentrations in the State. An area covering mostly southwestern Wisconsin, but including adjacent parts of Minnesota, Iowa, and Illinois, is called the "driftless area". It is not covered by glacial deposits but was likely overrun by glaciers at least once. The driftless area is underlain mostly by limestone, dolomite, and sandstone with moderate to high radon potential.

Glacial deposits in southern Wisconsin, northern and central Illinois, and western Indiana are primarily from the Green Bay and Lake Michigan lobes. The Green Bay and Lake Michigan lobes advanced from their source in the Hudson Bay region and moved southward into Illinois. These tills range from sandy to clayey and are derived mostly from shales, sandstones, and carbonate rocks of southern Wisconsin, the western Michigan Basin, and the northern Illinois Basin. A small part of eastern Illinois and much of western Indiana are covered by deposits of the Huron-Erie lobe, and west-central Illinois is covered by pre-Wisconsinan, mostly Illinoian, deposits. The Huron-Erie lobe entered Illinois from the east and moved primarily westward into the state. Huron-Erie lobe and pre-Wisconsinan glacial deposits are derived from shales, sandstones, siltstones, carbonate rocks, and coal of the Illinois Basin, and they are commonly calcareous due to the addition of limestones and dolomites of northern Indiana and Ohio and southern Ontario. In contrast, Lake Michigan lobe deposits contain significant amounts of dark gray to black Devonian and Mississippian shales of the Michigan Basin, accounting for the high clay content of Lake Michigan lobe tills. Unglaciated southern Illinois is part of the Mississippi Embayment of the Gulf Coastal Plain and has low radon potential.