World History of Radon Research and Measurement from the Early 1900’s to Today

In 1900, Dorn discovered the emanation in the uranium series that eventually became the well-known gas Rn. From 1900 through 1908, it was demonstrated that Rn is a radioactive gas found in tap water, highly condensable at low temperatures with a halflife of approximately 3.7 days and can be collected on charcoal by adsorption. Although, radon was discovered in 1900, the effects of prolonged exposure had been suspected and noted 300 years earlier among underground miners who developed lung cancer. During the period from 1924-1932, it was suggested that radon was the cause of high lung cancer incidence. In 1951, researchers at the university of Rochester N.Y. pointed out that the lung cancer health hazard was from the alpha radiation dose delivered by the radon decay products that deposited in the respiratory tract. The findings of the BEIR Committee Report VI, which was based on epidemiological studies in different groups of mines in the 1950’s and 1960’s and on laboratory studies, showed that from 60,000 miners over 2,600 developed lung cancer where only 750 were expected. Since 1998, the epidemiological study conducted in Iowa US, showed beyond any reasonable doubt that radon decay products cause lung cancer among women who lived at least twenty years in their homes. This paper will cover early radon measurements in soil, building material, ground water and in different air environments such as in the atmosphere, caves spas, underground mines and in residential indoor air environment. Radon measurements were conducted in many areas for diagnostic purposes. Radon was used as natural tracer to study air masses, vertical diffusion, and atmospheric studies, in earthquake prediction, and as a geological indicator for radium and uranium. In the early radon measurements, electroscopes, electrometers and primitive ionization chambers were used for many years. In the 1940’s fast pulse ionization chambers replaced total ionization chambers. From the mid 1950’s onwards a variety of radon measuring instruments were developed to assess the radon and radon decay product exposure to underground miners, workers at contaminated sites with uranium and radium tailings and to the general public in residential buildings. In the last twenty years, new instruments and methods were developed to measure radon by using grab, integrating and continuous modes of sampling. The most common are scintillation cell monitors, activated carbon collectors, electret ionization chambers, alpha track detectors, pulse and current ionization chambers and solid-state alpha detectors.