Radiation lifetime cancer risks from

Calculation of lung cancer risk for radon daughter exposure is based on factors developed by the National Council on Radiation Protection and Measurements (NCRP, 1984). The risk coefficients are expressed in terms of lifetime risk from lifetime exposure for a population of mixed ages, comparable to the standardized U.S. population, and range between one and two per 10,000 WLM of exposure. The percent increase in risk is related to a normal lifetime lung cancer risk of 0.041. 

NCRP has recommended that annual effective doses to individuals from any practice or source of 10 p.Sv or less are negligible (see Section 4.1.2.5.3). This dose is one percent of the dose limit for continuous exposure to all man-made sources combined discussed in the previous section, and it also is about one percent of the dose from natural background radiation, excluding radon (NCRP, 1987b). The recommended negligible individual dose corresponds to an estimated lifetime fatal cancer risk of about 4 X 10 5. 

Also unknown is the lifetime cancer risk following prenatal exposure to radiation. When advising pregnant women exposed to radiation, clinicians should consider that available data suggest that lifetime cancer risk from prenatal exposure is similar to, or slightly higher than, the cancer risk secondary to childhood exposure (Table 4.5). 

The lifetime cancer risks from prenatal radiation exposure are not yet known. The lifetime risk... 

Inhalation slope factors are central estimates in a linear model of the age-average, lifetime attributable radiation cancer incidence (fatal and nonfatal cancer) risk per unit of activity inhaled, expressed as risk per picocurie (pCi). qExternal slope factors are central estimates of the lifetime attributable radiation cancer incidence risk for each year of exposure to external radiation from photon-emitting radionuclides distributed uniformly in a thick layer of soil, expressed as risk/year per pCu per gram of soil. 

The risk estimates proposed by ICRP (1991) and UNSCEAR (2000) - for use in radiation protection - provide simple and robust estimates for the lifetime excess risk to die from radiation-induced cancer. But they facilitate only an overall, not an organ-specific estimate and are aimed at age- and gender-averaged groups of persons, such as the working population or the whole population of a country. 

Table 6.1 —Lifetime excess cancer mortality from a single exposure to 10 rad oflow-LET radiation per miOion males, as estimated with the absolute risk projection model and various dose-response models ...

Table. 2—Estimated lifetime excess cancer mortality from low-LET radiation per million males, as estimated by different dose-response models and risk projection models ...

If the exposure had been much smaller, the risk calculation would have been less direct and less certain. For purposes of risk reduction in public health, we may choose to err on the pessimistic side in risk estimations. For purposes of attribution, however, we want to make best estimates. Most of the numbers in Ikble 8.4 are overestimates of the risks. For radiation-induced leukemia, as described in Section 6.1.2, the best dose-incidence model might be lineai>quadratic and not linear. Thus, someone exposed to 50 mSv (5 rem) might be considered, on a linear extrapolation basis, to have a radiation related lifetime risk of cancer mortality of 10 (2 x 10 Sv 2 x 10 rem ), or a lifetime risk of mortality from leukemia of approximately 1.5 x 10 (0.3 x 10" Sv 0.3 X 10 rem ). The natural lifetime risk of mortality from leukemia other than chronic lymphocytic leukemia is approximately 56 x 10 . Therefore, the percent attribution to radiation according to the linear model would be ... 

On the basis of available evidence, the Committee on the Biological Effects of Ionizing Radiations (called BEIR V Committee) has recommended use of a lifetime excess risk (i.e., normal risk has been subtracted) of 0.08 per 100 rad for death from y-ray- or X-ray-induced cancer. This risk applies to the average person in the United States population (all ages considered) exposed to doses up to 10 rad, when... 

Because radiation exposure can be cumulative, there are no truly safe levels of exposure to radioactive materials. Radiation does not cause any specific diseases. Symptoms of radiation exposure may be the same as those from exposure to cancer-causing materials. The tolerable limits for exposure to radiation that have been proposed by some scientists are arbitrary. Scientists concur that some radiation damage can be repaired by the human body. Therefore, tolerable limits are considered acceptable risks when the activity benefits outweigh the potential risks. The maximum annual radiation exposure for an individual person in the United States is 0.1 REM. Workers in the nuclear industry have a maximum exposure of 5 REMs per year. An emergency exposure of 25 REMs has been established by The National Institute of Standards and Technology for response personnel. This type of exposure should be attempted under only the most dire circumstances and should occur only once in a lifetime. 

National Cancer Institute (1998) Calculation of the estimated lifetime risk of radiation-related thyroid cancer in the United States from the Nevada Test Site fallout, 1997. Available at http //rec.nci.nih.gov/massmedia/falloutQ %26A.html. Accessed July 1, 1998... 

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