Assessing exposure to granite countertops—part 1: Radiation

Abstract

Humans are continuously exposed to low levels of ionizing radiation. Known sources include radon, soil, cosmic rays, medical treatment, food, and building products such as gypsum board and concrete. Little information exists about radiation emissions and associated doses from natural stone finish materials such as granite countertops in homes. To address this knowledge gap, gross radioactivity, g ray activity, and dose rate were determined for slabs of granite marketed for use as countertops. Annual effective radiation doses were estimated from measured dose rates and human activity patterns while accounting for the geometry of granite countertops in a model kitchen. Gross radioactivity, g activity, and dose rate varied significantly among and within slabs of granite with ranges for median levels at the slab surface of ND to 3000 cpm, ND to 98,000 cpm, and ND to 1.5EÀ4 mSv/h, respectively. The maximum activity concentrations of the 40 K, 232 Th, and 226 Ra series were 2715, 231, and 450 Bq/kg, respectively. The estimated annual radiation dose from spending 4 h/day in a hypothetical kitchen ranged from 0.005 to 0.18 mSv/a depending on the type of granite. In summary, our results show that the types of granite characterized in this study contain varying levels of radioactive isotopes and that their observed emissions are consistent with those reported in the scientific literature. We also conclude from our analyses that these emissions are likely to be a minor source of external radiation dose when used as countertop material within the home and present a negligible risk to human health.

Assessing exposure to granite countertops—part 2: Radon

“…All flux calculations were conducted in the same manner as for the full-slab surface testing. In addition to the flux measurements, the radium-226 ( 226 Ra) activity of each corner sample was measured using gamma spectroscopy with a high-purity germanium detector, the details of which are described in Myatt et al (2009).…”

Survey of Radioactive Items in the Home

“…This represents an annual dose of about 7.1 mrem/y based on an exposure of 1 h/d for 365 d (5). Use of that type of granite as more than a kitchen countertop, for only 4 h a day, well exceeds 25% of an individual's annual effective dose of 100 mrem/y from a single manmade source.…”

“…Known radioisotopes found in granite include uranium and thorium; however, these two make up very small portions of granite (4,5). Radon gas ( 222 Rn) also is known to be a natural constituent of natural stones, such as granite, used as building materials (6).…”

Radiological Hazards for Marble and Granite Used at Shak El Thouban Industrial Zone in Egypt

“…The lead shield contained two inner concentric cylinders of copper and cadmium to prevent interference X-rays by lead. The energy calibration of the HPGe spectrometer was carried out by using standard point sources ( Th with activities of 2120.37 and 1333.96 Bq, respectively and potassium chloride KCl solutions with activity 15.9 Bq [11], contained in the same cylindrical bottles with the same volume 250 cm 3 and having the same nature as the investigated samples. The standards and the samples were prepared with a uniform geometry.…”

“…Over the past decade, a number of studies have been reported on the activity concentrations of natural radionuclides for marble and granite samples obtained from different countries in the world [1][2][3][4][5][6][7].…”