Unknown Quantity: Regulating Radionuclides in Tap Water

Exposure to naturally occurring and man-made radionuclides can occur through drinking water or via inhalation or dermal pathways while showering or during other contact with the water. R adioactivity surrounds us; each day we are exposed to a certain amount by virtue of being alive on planet Earth. Some of this exposure comes from radioactive substances (radionuclides) that occur naturally in a wide variety of geologic and soil formations. Occasionally these naturally occurring substances become more concentrated or accessible through human activities such as mining and nuclear energy production, resulting in greater potential for exposure than their original natural occurrence would suggest. Other radionuclides are artificially created. Residents in almost all parts of the United States live on lands that contain minor to substantial concentrations of radionuclides of one type or another. These substances often make their way into tap water, leading to exposures by ingestion, inhalation, or dermal pathways during showering or other contact with the water.