The legacy of milling uranium in Durango from 1948 to 1963 has left the area with residual radiation that continues to be a health concern, a San Juan Basin Health Department official says.
Half of Durango's houses have a radon concentration of more than 4 picocuries per liter of air - the Environmental Protection Agency level of concern, Marian Schaub, who oversees the department's radon testing, said Friday. Sixty-three percent of houses in Durango have radon concentrations above 2 pCi/l.
"There is no safe level of radon, which is the product of decaying uranium," Schaub said. "Radon is a naturally occurring gas that can't be seen, smelled or tasted, but it's found in varying concentrations everywhere."
In 2008, the health department and the Colorado State University Cooperative Extension distributed 400 free radon test kits. Results from the 132 that were returned by the Air Chek Inc. laboratory in Mills River, N.C., show readings from 0.3 to 91.1 pCi/l. Other scary readings included 77.8, 21.8, 19.8 and 14.3 pCi/l.
"The test kits were free, but there's a whole carload that weren't returned," Schaub said.
Schaub seconded Gov. Bill Ritter's proclamation that designates January as Colorado Radon Action Month and urges residents to test their homes for the gas, which is the second-leading cause of lung cancer in smokers and the leading cause in nonsmokers.
"The contribution of radon to lung cancer is only 'suspected' by some sources," Schaub said. "But the only way to know for sure is an autopsy."
This month is a good time to test for radon, Schaub said, because snow seals soil and because nature abhors a vacuum, radon in the ground will find its way through cracks into the house where air pressure is less. Householders tend to keep windows and doors closed, which traps radon in the structure.
Radon is sometimes found in one house and not in the house next door.
The Environmental Protection Agency classifies almost all of Colorado as a Zone 1 - where potential concentrations of radon exceed 4 picocuries per liter of air. Twelve counties - La Plata, Archuleta, San Juan, Mineral, Hinsdale, Alamosa, Conejos, Costilla, Saguache, Routt, Rio Grande and Eagle - are classified as Zone 2 - potential concentrations of the gas measure 2 to 4 pCi/l. Colorado has no Zone 3 area where radon concentrations measure less than 2 pCi/l.
Durango is in a Zone 2 radon area, but that's somewhat misleading. A uranium mill across the Animas River from Santa Rita Park, where the Vanadium Corp. of America refined the radioactive material for atomic-bomb research from 1948 to 1963, left its mark, Schaub said. In the 1980s, the U.S. Department of Energy began cleaning up uranium refining sites, including 10 in Colorado, among which was the Durango mill. In Durango, 2.5 million cubic yards of low-level radioactive material was removed and buried in Bodo Canyon south of Smelter Mountain and capped with rock and earth.
But 300,000 cubic yards of radioactive tailings were left, Schaub said. The Uranium Mill Tailings Removal Action project found hot deposits on 548 private properties, but only 128 were cleaned. The remainder, because of owner refusal or other reasons, were not.
Radon concentrations vary from neighborhood to neighborhood, Schaub said. Hot areas in the past included the Animas Valley, the area around 32nd Street east of Main Avenue and a stretch of Camino del Rio near its junction with Main Avenue. Also, uranium tailings were used as a soil enhancer and in construction materials including stucco and bricks, concrete and backfill, she said.