Uranium levels and radon potential in selected areas north of Phoenix, in the St. Johns Area, and north of Tuba City, Arizona

Radon is a colorless, odorless gas produced by the natural radioactive decay ofuranium. The U. S. Environmental Protection Agency has determined that exposure to indoor radon increases human risk of developing lung cancer. Indoor-radon levels generally correlate with uranium concentration in underlying rocks and soil, and some areas of Arizona are known to have elevated levels ofuranium. In many areas in Arizona calcareous lake beds deposited in middle to late Cenozoic time have elevated uranium levels and these rocks are by far the most significant potential radon source in Arizona (Spencer, 1992, 1993). With funding from an EPA State Indoor Radon Grant (SIRG year 8, Grant Kl009544- 08-0), the Arizona Geological Survey conducted a survey ofuranium levels in previously unstudied calcareous lake beds in the New River area north of Phoenix (Maricopa County), calcareous rocks that are probably lake beds in the St. Johns area (Apache County), and limestones of uncertain age at Preston Mesa north of Tuba City (northeastern Coconino County, Navaho Indian Reservation). A variety of other rock types were also examined in the New River area. Uranium concentrations were measured using a portable gamma-ray spectrometer. The spectrometer survey followed the methods outlined in Duncan and Spencer (1993a) and the same equipment was used during both investigations. The results and an evaluation of their significance are presented here. ( 13 pages)Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu