some spring waters and hot springs. The towns of Misasa, Japan, and Bad Kreuznach, Germany boast radium-rich springs which emit radon, as does Radium Springs, New Mexico. Radon exhausts naturally from the ground, particularly in certain regions, especially but not only regions with granitic soils. Not all granitic regions are prone to high emissions of radon, for instance while the rock which Aberdeen is on is very radium rich the rock lacks the cracks required for the radon to migrate. In other nearby areas of Scotland (to the north of Aberdeen) and in Cornwall/Devon the radon is very much able to leave the rock. Radon is a decay product of radium which in turn is a decay product of uranium. One can get maps of average radon levels in houses to help in planning radon mitigation measures for homes. While high uranium in the soil/rock under a house does not always lead to a high radon level in air, a positive correlation between the uranium content of the soil and the radon level in air can be seen. In air Radon harms indoor air quality in many homes. (See "Radon in Houses" below.) Radon (222Rn) released into the air decays to 210Pb and other radioisotopes and the levels of 210Pb can be measured. It is important to note that the rate of deposition of this radioisotope is very dependent on the season. Here is a graph of the deposition rate observed in Japan. In groundwater Well water can be very rich in radon; the use of this water inside a house is another route allowing radon to enter the house. The radon can enter the air and then be a source of exposure to the humans, or the water can be consumed by humans which is a different exposure route. Radon in rainwater Rainwater can be highly radioactive due to high levels of radon and its decay progenies 214Bi and 214Pb; the concentrations of these radioisotopes can be high enough to seriously disrupt radiation monitoring at nuclear power plants. The highest levels of radon in rainwater occurs during thunderstorms, and it is hypothesized that radon is concentrated in thunderstorms on account of the atom's positive electrical charge. Estimates of the age of rain drops have been obtained from measuring the isotopic abundance of radon's short-lived decay progeny in rainwater. In the oil and gas industries Water, oil and gas from