Granite is an igneous rock formed as liquid rock cooled. It is typically in the earth and requires mining in order to get it to your countertops. Because of this, there was a large scare about the claims that granite may provide a significant health risk through radon emission. Thus far, the EPA thinks that granite is safe for homes.
Granite contains various naturally occurring radioactive elements (like uranium and thorium) that decay over time. As these elements decay, they emit radon, which is shown to cause lung cancer from prolonged exposure to a certain threshold of it in the air. This is why the main way to fix any radon problems in your home is simply to install a ventilation system to keep those levels within a normal range.
The biggest danger of radon in your home is from the soil around and under your foundation, not your countertops. As many as 1 in 15 homes may have a significant concentration of radon, so it’s important to either test your home yourself or hire an expert. In addition to the radon emitted, there is some evidence that granite can emit small amounts of both gamma and beta radiation. At this point, the EPA believes that granite countertops do not threaten an individual’s health. The amounts emitted are believed to be within the range of normal background radiation we receive every day.