Can Cat Litter Be a Source of Indoor Radon ?

Emanation of radon (Rn) from several brands of cat (kitty) litter was measured with a continuous radon monitor. Radon emanating from the cat litters, encapsulated in an airtight container, produced equilibrium concentrations below 1.2 pCi/g. The measured radon flux was below 10 pCi/kg-hr for all the cat litters. Although each of the samples emitted a measurable amount of radon, the emanation is too small to raise indoor radon concentrations. The cat litters were measured with gamma-ray spectroscopy to identify and quantify the naturally occurring radionuclides in the samples. Secular equilibrium for the U and Th radioactive-decay series was evident. Introduction Radioisotopes of the three naturally occurring radioactive-decay series, headed by Th, U, and U, are ubiquitous in soils. Although a different isotope of radon is formed in each of the radioactive-decay series, only Rn has a sufficiently long half-live (3.8 d) that it often occurs at elevated concentrations in indoor air. The Rn isotope, commonly and here referred to as radon, and its decay products have been linked by epidemiological studies to an increased risk of lung cancer, causing approximately 21,000 lung-cancer deaths (Lubin, 1997) annually in the United States (US). A majority of radon entry into a house occurs at the soil-foundation interface, with minor contributions from groundwater use, building materials, and outdoor air. In the past year, several homeowners and radon mitigators have inquired about radon emanation from cat litter, with the latter group noting increased radon levels in rooms containing a litter box. Given the health implications and the paucity of measurement data, goals of the