Occupational Radiation Exposures

For radiation doses <0.5 Sv, there is no clinically observable iacrease ia the number of cancers above those that occur naturally (57). There are two risk hypotheses the linear and the nonlinear. The former implies that as the radiation dose decreases, the risk of cancer goes down at roughly the same rate. The latter suggests that risk of cancer actually falls much faster as radiation exposure declines. Because risk of cancer and other health effects is quite low at low radiation doses, the iacidence of cancer cannot clearly be ascribed to occupational radiation exposure. Thus, the regulations have adopted the more conservative or restrictive approach, ie, the linear hypothesis. Whereas nuclear iadustry workers are allowed to receive up to 0.05 Sv/yr, the ALARA practices result ia much lower actual radiatioa exposure. 

Fig. 7. U.S. auclear power plant occupational radiation exposure, where ( ) corresponds to total radiation exposure, ( ) to the electricity generated, and (— -) to the radiation exposure per unit of electricity 5(Sv/(MW-yr)) (60). Courtesy of the Electric Power Research Institute.

Some years ago it was realized that the indoor inhalation of the short-lived radon daughters constitutes the most important contribution to the radiation exposure of the general population (Unscear, 1982). The working level concept has been introduced in the domestic environment due to the success of the concept in the occupational environment and due to a lack of experimental data on the relative and absolute magnitudes of the transformation and... 

Many states in the U.S. are currently involved in large scale surveys to measure radon levels in homes in an attempt to assess the environmental risk from radon and radon daughter exposure. Radon daughters deliver the largest radiation exposure to the population and it is estimated that 0.01% of the U.S. population (23,000 persons) are exposed from natural sources to greater than those levels allowed occupationally (4 WLM/yr) (NCRP, 1984). 

The calculation of effective dose equivalent is sometimes used even when reporting values for natural radioactivity. The concept of effective dose equivalent was developed for occupational exposures so that different types of exposure to various organs could be unified in terms of cancer risk. It is highly unlikely that the general population would require summation of risks from several sources of radiation exposure. 

Individual dose assessment requires radiological data on all external and internal sources contributing to occupational and non-occupational radiation exposure (Steinhausler and Pohl, 1983). This is of particular importance in the case of low level Rn-d exposure, as man is always exposed to Rn-d at varying levels through all stages of life, e.g. at school, home or work. The resulting lifetime risk from this chronic exposure is influenced by the latent... 

The following expressions were employed for health risk as a result of the radiation exposure incurred during occupancy of a property the cancer risk per individual for gamma and/or for radon daughter exposure the individuals percent increase in cancer risks relative to the respective, normal cancer risks and the number of projected excess cancer deaths due to the radiation exposure (external and internal) for the number of occupants at each property. 

Occupational radiation exposure, at nuclear power facilities, 17 552-553 Occupational Safety and Health Administration (OSHA), 21 568. 

Radiation Safety Guide. 1999. Occupational radiation exposure monitoring External monitoring. http //www.nih.gov/od/ors/ds/rsb/rsguide/orem.htm. 

Under LNT, the risks of developing cancer from occupational radiation exposure are about the same as the risks of any other occupational illness or injury—about 1 in 10,000. By comparison, the background cancer death rate is about 1,600 in 10,000 (16%), and about 1 person in 7,000 dies each year in traffic accidents (more than 40,000 in the year 2000). For the vast majority of radiation workers, the drive to work is far more hazardous than their occupational radiation exposure, even using the LNT model. 

The survivors from atomic bombs dropped in August 1945 were analyzed. Within 1 km of the epicenter 64,000 people were killed by the blast. From 1-2 km of the epicenter, people received doses as high as several Sv. At more than 2.5 km, irradiation was not significantly above background. Risk estimates are important because they are used for occupational exposure guidelines. The latest updates report that 5% of the solid cancer deaths and 0.8% of the noncancer deaths were estimated to be due to radiation exposure (>9,000 cancer deaths >31,000 noncancer deaths 47 years of follow-up). 

The occupational, accidental, and wartime experiences have provided the basis for the estimation of risk to humans following radiation exposure. However, cosmic, cosmo-genic, inhaled, and in-body radiation deliver total body effective doses of 3 becquerel per year total effective dose. The average radon concentration indoors is 40 becquerel... 

Philipp, G., Pfister, H. and Pauly, H., Occupational radiation exposure from natural radionuclides in phosphate fertilizers and its contribution to the exposure of the population in the FRG (in German). In Kellermann H.J. (ed.). Radioactivity and Environment, Vol. 12, pp. 890-901. Fachhverband fiir Strahlenschutz, Karlsruhe, 1978. 

Many of the recommendations of the ICRP and other radiation protection groups regarding radiation exposure have been incorporated into regulatory requirements by various countries. For the U.S. Department of Energy facilities, radiation exposure limits are found in Title 10, Part 835 of the Code of Federal Regulations (10CFR835). Table 3.1 provides a summary of the dose limits for occupational external exposures. 

Morgenstern H, Ritz B. Effects of radiation exposure and chemical exposures on cancer mortality rate among Rocketdyne workers A review of three cohort studies. Occup Med2001 16(2) 219—37. 

Hazelton, W. D., Moolgavkar, S. H., Curtis, S. B., Zielinski, J. M., Ashmore, J. P, and Krewski, D. (2006). Biologically based analysis of lung cancer incidence in a large Canadian occupational cohort with low-dose ionizing radiation exposure, and comparison with Japanese atomic bomb survivors. J Toxicol Environ Health Part A 69, 1013-1038. 

Seel, E. A., Zaebst, D. D., Hein, M. J., Liu, J., Nowlin, S. J., and Chen, P. (2007). Inter-rata- agreement for a retrospective exposure assessment of asbestos, chromium, nickel and welding fumes in a study of lung cancer and ionizing radiation. Ann Occup Hyg 51, 601-610. 

K. W., Occupational Radiation Exposure, BNES Paper 44, London (1991), p. 129. 

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