Radon in Water
Radon is produced by the radioactive decay of radium in the ground. Granites and other rocks may contain high concentrations of radium and produce significant amounts of radon. Aquifers in these rocks accumulate the radon, increasing the concentration in the water. The highest radon concentrations in water are found in ground water supplies. Radon is more common in smaller ground water supplies . . . those serving 25 or fewer people.