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Radon Gas - Why Is It Dangerous?

The known health hazard associated with exposure to radon is an increased risk of lung cancer. Exposure to radon and its decay products is the second-leading cause of lung cancer in America after cigarette smoking.

According to Dr. L. Grodzins of the Massachusetts Institute of Technology, in a document published in 1987 for Beckman Instruments, Inc., the decay of radon gives off more radiation than the amount an average nuclear power plant employee is exposed to.
Early risk assessments have been more concerned about the radon in air than the radon in water. In fact, the only danger from radon in drinking water was thought to be that this radon could and did evaporate into the air.
Today, more is known about the effects of radon ingested in drinking water. According to studies performed at Massachusetts General Hospital as part of the EPA's effort to regulate radon, it is now known that ingested (radon in drinking water) is first present for a significant length of time in the stomach, and then moves, in smaller quantities, to the small intestine, upper large intestine, lower large intestine, and from there to the portal blood, where it is rapidly carried to the liver, and to airspaces in the lung tissue. Radon may also reach general body tissue, where it is distributed uniformly.
Although the lung tissue generally receives less of a dosage from ingested radon than it does from inhaled radon, we already know that lung cancer is a proven effect of radon exposure, so it is possible that radon in water contributes to lung cancer rates as well.
Studies indicate that the stomach receives the greatest dose of radiation from ingested radon. The relationship between radon exposure and stomach and intestinal cancer is highly uncertain, and a better understanding of the actual risk factors involved awaits further epidemiological studies.
It has been suggested that the alpha particles released by the nucleus of radon atoms and radon progeny as they decay, are responsible for most of the bodily damage caused by radon. When alpha particles are inhaled they may attach to lung tissue. Alpha particles can enter the lungs freely in the form of radon gas, or as a radon decay product attached to dust, smoke, lint or biological aerosols.
While in the lung tissue, the energy emitted by the alpha particles has the potential to damage DNA molecules. The damaged DNA molecules may repair themselves, may die, or may replicate more damaged DNA molecules. If damaged cells are replicated, the danger of lung cancer arises. Exposure to radon does not always cause lung cancer, but it does increase a person's risk.
Research has shown that lung cancer rates among miners of uranium, iron, and other hard rock minerals, who have worked within comparatively high quantities of radon, are higher than the lung cancer rates of underground miners of coal and gold, who have worked with comparatively low quantities of radon.

This research also shows that the higher the radon concentrations were, and the longer the exposure, the more serious the risk of lung cancer grew. The lung cancers usually appeared at least 5 to 10 years after exposure.
Studies of animals have shown that dogs, mice and rats, whose lungs are similar to humans, are also at increased risk of contracting lung cancer from exposure to radon and radon decay products.