Supreme Granite Kitchen Island – Project Manager: Randy Wilson. A comprehensive new scientific study sponsored by the Marble Institute of America definitively shows that granite countertops are an insignificant source of radon in the home and that 99.95% of countertops produce lower radon concentrations than are typically found outdoors in the U.S. The study also concluded that in normal applications there is no risk granite countertops will produce radon concentrations even close to levels the U.S. Environmental Protection Agency says require remediation (4 picocuries/liter).