World History Of Radon Research AndMeasurement From The Early 1900's To Today

摘要

In 1900, Dorn discovered the emanation in the uranium series that eventually becamethe well-known gas ~(222)Rn.From 1900 through 1908, it was demonstrated that ~(222)Rnis aradioactive gas found in tap water, highly condensable at low temperatures with a half-life ofapproximately 3.7 days and can be collected on charcoal by adsorption. Although, radon wasdiscovered in 1900, the effects of prolonged exposure had been suspected and noted 300 yearsearlier 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 wasfrom the alpha radiation dose delivered by the radon decay products that deposited in therespiratory tract. The findings of the BEIR Committee Report VI, which was based onepidemiological studies in different groups of mines in the 1950's and 1960's and on laboratorystudies, showed that from 60,000 miners over 2,600 developed lung cancer where only 750 wereexpected.Since 1998, the epidemiological study conducted in Iowa US, showed beyond any reasonabledoubt that radon decay products cause lung cancer among women who lived at least twenty yearsin their homes. This paper will cover early radon measurements in soil, building material, groundwater and in different air environments such as in the atmosphere, caves spas, underground minesand in residential indoor air environment. Radon measurements were conducted in many areas fordiagnostic purposes. Radon was used as natural tracer to study air masses, vertical diffusion, andatmospheric studies, in earthquake prediction, and as a geological indicator for radium anduranium. In the early radon measurements, electroscopes, electrometers and primitive ionizationchambers were used for many years. In the 1940's fast pulse ionization chambers replaced totalionization chambers. From the mid 1950's onwards a variety of radon measuring instruments weredeveloped to assess the radon and radon decay product exposure to underground miners, workersat contaminated sites with uranium and radium tailings and to the general public in residentialbuildings. In the last twenty years, new instruments and methods were developed to measure radonby using grab, integrating and continuous modes of sampling. The most common are scintillationcell monitors, activated carbon collectors, electret ionization chambers, alpha track detectors, pulseand current ionization chambers and solid-state alpha detectors.