Some have proposed that "low" exposures to radiation may be beneficial, a hypothesis referred to as "hormesis". However, at "low levels" uncertainty persists as to whether the dose-response relationship is linear and whether there is a dose threshold, below which there is no risk. There is no doubt as to the existence of a hazard and exposures are known with reasonable accuracy. įor ionizing radiation, the principal uncertainty at present lies in the form of the dose-response relationship. Such medical exposures have now surpassed radon as the leading contributor to radiation exposure in the United States as use of diagnostic imaging has risen sharply. Additionally, the millions of people receiving radiation for diagnostic and therapeutic purposes need to have an understanding of the attendant risks. We are also learning that there is a spectrum of susceptibility to radiation that needs to be taken into account. Determination of the acceptability of risk requires an assessment of the magnitude of risk and a societal judgment as to acceptability of the estimated risk. There is a need to minimize risk at the population level and to assure that risks to individuals do not reach unacceptable levels, particularly for workplace exposures. Risk assessment has become fundamental to strategies for limiting cancer risks associated with radiation exposures. Most recently, a National Research Council Committee gave emphasis to the need to make certain that questions were properly framed to assure that the findings of a risk assessment will prove valuable for risk management. The framework is useful, not only for assembling evidence on risk, but for identifying evidence gaps, attendant uncertainties, and related research needs. Many subsequent reports from the National Research Council and other groups have refined the elements of risk assessment, though the four components have proved to be invaluable in approaching risk questions. A 1983 report of the United States National Research Council, Risk Assessment in the Federal Government: Managing the Process (widely referred to as the "red book") set out four elements of risk assessment: hazard identification (is there a problem?), dose-response assessment (how does risk vary with dose or exposure?), exposure assessment (what is the population's pattern of exposure?), and risk characterization (what is the magnitude of the problem and what are the key uncertainties in that understanding?). Risk assessment is an applied methodology, used to characterize risks to populations as the basis for risk management. Exposures are regulated through an evidence-based approach that is used to characterize risks, drawing primarily on the epidemiological evidence (Figure 1). Radiation exposures are ubiquitous, coming from medical and industrial applications and from naturally occurring sources. The data have been sufficient to support a radiation protection approach that is grounded in the epidemiological evidence (see below). The resulting data base is extensive for several types of radiation including X and gamma radiation and radon. Many cohort studies have followed with radiation exposures received through therapeutic intervention or occupation, or by accident. This cohort has proved to be a remarkably informative resource, providing a temporal profile of leukemia and cancer associated with the blast and a robust data set for making quantitative estimates of risk. A large, prospective cohort was designed, the Lifespan Study of 120,000 survivors, which is still in progress. Radiation epidemiology was launched when a program of studies was initiated by the then Atomic Bomb Casualty Commission (eventually to become the Radiation Effects Research Foundation) to determine the consequences of radiation exposure from the nuclear blasts at Hiroshima and Nagasaki.
By World War II, there was sufficient understanding of the risks of radiation to motivate a program of protection for workers at the Manhattan Project in the United States. In 1944, based on more formal epidemiological inquiry, an excess of leukemia was reported among radiologists in the United States. Several clusters of radiation-caused cancer were described over the ensuing decades: radon and lung cancer in underground metal miners in eastern Europe, and osteogenic sarcoma in radium dial painters.
#Radium effects onhealth skin
By 1902, the first radiation-caused skin cancer was identified and the first radiation-caused leukemia case followed in 1911. Ionizing radiation was discovered in 1895 by Wilhelm Conrad Roentgen, and its utility for diagnostic purposes was quickly recognized.
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