AZGS | Menu
Geologic Hazards in Arizona | Radon

"Indoor radon is the second-leading cause of lung cancer in the United States and breathing it
over prolonged periods can present a significant health risk to families all over the county..."

- U.S. Surgeon General Richard H. Carmona in January 2005 warning
the American public of the hazards of long-term exposure to radon

Radon: Chemical Symbol: Rn, Atomic Mass: 86, Atomic Number: 222

A Rundown on Radon.   Radon (Rn) is a noble gas formed by radiogenic decay of uranium.  Radon is a colorless and odorless radiogenic gas.  Its most common radiogenic isotope, 222Rn, has a half-life of 3.8 days; one half-life is the period of time during which one-half of the parent isotope decays to form daughter isotopes.  (So if you began with 1000 222Rn, 3.8 days later, you would have 500 222Rn isotopes and 500 daughter isotopes).  222Rn decays spontaneously to form daughter isotopes.

Radon in Arizona.   Fortunately, indoor radon levels in Arizona are among the lowest in the U.S.  In the late 1980’s and early 1990’s, AZGS geoscientists, led by senior geologist, Jon Spencer, made a concerted effort to understand the geologic hazard of radon in Arizona.  Online publication summarizing the results

While radon levels in Arizona are generally low, there are several hot spots throughout the state.  Some of the more prominent radon hot spots include:  Tucson (the area around Cardinal Avenue);
the Cave Creek Area; parts of the Verde Valley; and the Granite Dells near Prescott.  The US EPA recommends that all homes be tested for radon levels.  A primer on how you can test your home

How does radon compare as a health risk with other common types of risk?  Look at the chart below from the US Environmental Protection Agency to see how radon fares as a mortal health risk in comparison with drunk driving, drowning, home fires, and falls in the home as causes of death annually in the US. 

So how does radon get into your house?   Well, there are a number of pathways that radon gas can take to enter a home.  Chief among these are:

  • Cracks in solid floors or walls
  • Along gaps around service pipes
  • Via your water supply

(Click on image to right to enlarge. By Geological Survey of Canada)

File(s) Available for Download:

Radon Gas in 1986

Radon Update in 1987

For More Information :

U.S. Environmental Protection Agency – some marvelous and robust information on radon, its origin, health effects, and how to mitigate risk.

Also from the U.S. EPA:

Arizona Dept. of Health Services150 N. 18th Avenue
Phoenix, AZ  85007
Phone: (602) 542-1001
Fax: (602) 542-0883

[see full list of Health and Human Services - Family, Health, Safety]

This page is best viewed with Firefox | For website feedback: | Copyright © The Arizona Geological Survey, 2012. All rights reserved.