Annual effective dose

A survey of the radon concentrations in a representative sample of more than 2000 dwellings in the UK has been completed and provisional results are now available. On average, concentrations are 29% lower in bedrooms than in living areas. The mean radon concentration weighted for room occupancy is 22 Bq m 3. Assuming an equilibrium factor of 0.35 and a mean occupancy of 75%, the mean annual exposure in UK homes is assessed as 0.08 Working Level Months (WLM) and the mean annual effective dose equivalent as 0.43 mSv. 

The average annual effective dose equivalent received by a member of the UK population is currently estimated to be 2150 ySv. Of this total, 87% arises from exposure to radiation of natural origin, the largest single contributor being inhalation of the short-lived decay products of radon. This exposure occurs predominantly in the home. 

This value of 0.43 mSv for the average annual effective dose equivalent for the UK as a whole is somewhat lower than the currently used value of 0.70 mSv (Roberts and Hughes, 1984). The difference arises partly from taking into account the lower exposure in bedrooms revealed in the national survey. Another reason is that no allowance is made in this survey (Table 2) for exposure received during the 15% of the time spent indoors at other locations nor while in the open. 

The average concentration of radon in outdoor air in the UK is 2.6 Bq m"3. Comprehensive data on the equilibrium factor in outdoor air in the UK is not available. Assuming equilibrium, the average exposure to radon decay products received by a member of the UK population during the 10% of time spent in the open is 0.0036 WLM, an annual effective dose equivalent of 0.02 mSv. 

On the basis of a conversion coefficient of 5.5 mSv WLM"1, occupants of the vast majority of dwellings in the UK receive annual effective dose equivalents less than 2 mSv. Even in the areas surveyed because of their potential for high radon exposures, the annual effective dose equivalents are unlikely to exceed a few tens of mSv. However, in certain areas of Cornwall and Devon, annual effective dose equivalents higher than 25 mSv may be received in a small percentage of dwellings. In some dwellings more than 50 mSv per year may be received. 

It is noted that the ICRP has assumed a higher conversion coefficient between annual effective dose equivalent and radon concentration (ICRP, 1984) in recommending an action level for remedial measures in homes, i.e. 1 mSv y"1 per 10 Bq m"3 of equilibrium equivalent radon gas concentration (9 mSv per WLM). If this conversion coefficient were applied to our regional survey data, we would estimate, from the distribution parameters given in table 3, that about 15% of the residents of certain areas of Devon and... 

Annual effective dose equivalent to humans from natural sources of ionizing radiation... 

Annual effective dose equivalent from nuclear weapons testing to humans in the north temperate zone... 

Table 32.4 Annual Effective Dose Equivalent to Humans from Natural Sources of Ionizing Radiation...

Table 32.7 Annual Effective Dose Equivalent from Nuclear Weapons Testing to Humans in the North Temperate Zone... 

Occupational - the committed effective dose equivalent (Internal) and annual effective dose equivalent (external) combined... 

Exposure to radiation from man-made sources is estimated to deliver an average annual effective dose equivalent of about 0.6 mSv (60 mrem) to the general population (Thble 4.1). The largest contribution comes... 

Table 4.1 —Estimates of annual effective dose equivalent to members of the U.S.

Radiation Dose Limits. For routine exposure of individual members of the public to all man-made sources of radiation combined (i.e., excluding exposures due to natural background, indoor radon, and deliberate medical practices), NCRP currently recommends that the annual effective dose should not exceed 1 mSv for continuous or frequent exposure or 5 mSv for infrequent exposure. The quantity effective dose is a weighted sum of equivalent doses to specified organs and tissues (ICRP, 1991), which is intended to be proportional to the probability of a stochastic response for any uniform or nonuniform irradiations of the body (see Section 3.2.2.3.3). 

NCRP (1993a) also has emphasized the importance of source constraints in radiation protection of the public. NCRP has reaffirmed a previous recommendation (NCRP, 1984b 1987a) that whenever the potential exists for routine exposure of an individual member of the public to exceed 25 percent of the limit on annual effective dose as a result of irradiation attributable to a single site, the site operator should ensure that the annual effective dose to the maximally exposed individual from all man-made sources combined does not exceed 1 mSv on a continuous basis. Alternatively, if such an assessment is not conducted, no single source or set of sources under one control should result in an individual receiving an annual effective dose of more than 0.25 mSv. 

The recommended limit on annual effective dose of 0.25 mSv per source corresponds to an estimated lifetime fatal cancer risk of about... 

X 10 3. Annual effective doses in the range of 0.25 to 1 mSv from all man-made sources combined are acceptable if they are ALARA. However, doses toward the upper end of this range are regarded as only barely tolerable (ICRP, 1991), and doses below this range are expected to be justifiable and achievable in most cases, based on site-specific application of the ALARA principle. Therefore, lifetime risks from routine exposure to all man-made sources combined usually should not exceed about 1 X 10 3. 

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. 

For each generic exposure scenario to be used in classifying waste, and taking into account all relevant exposure pathways in each scenario, calculate the dose per unit concentration of each hazardous substance in the waste. These doses generally would be the highest values calculated over an assumed time frame for the risk assessment (see Section 6.4.5.3), taking into account the time-dependence of the concentrations of hazardous substances in the waste. For example, the quantity calculated for radionuclides would be the annual effective dose (sievert) per unit activity concentration (Bq nr3), and the quantity calculated for hazardous chemicals would be the dose (intake, mg kg 1 d-1) per unit concentration (kg m 3). 

For exposure indoors of the general population, it is more useful to work in terms of the concentration of radon than the concentration of decay products. Brown et al. (1986) found the average concentration of 222Rn in Cornish houses to be 300 Bq m-3, and Nero (1988) has estimated that 2% of homes in the USA have similar or higher concentrations. Assuming an annual effective dose equivalent of 80//Sv... 

The calculation of population radiation effects is performed on the basis of different atmosphere stability categories. The estimated maximum annual effective dose for Severodvinsk population at the boimdary of the Sanitary Protection Area (500 m from radioactive release point) will be 0.1 pSv. It is considerably less than ImSv (the population dose limit under normal operation conditions in accordance with Radiation Safety Codes -NRB-99). 

Maximum annual effective dose for Zvezdochka persoimel as a result of radionuclide release to the environment under normal condition of NS dismantling process is 3.4 pSv. Maximum annual effective dose for Severodvinsk population at the boimdary of Sanitary Protection Area does not exceed 1.0 pSv. The indicated radiation doses are considerably less than annual dose from natural radiation backgroimd. 

The NCRP recommends an annual effective dose for continuous members of the public in some circumstances of 1 mSV (100 mrem). This value is in addition to natural background level of irradiation approximately twice that (2mSv 200 mrem). In this context, the NIRL was taken to be 1/100 of this level, or 0.01 mSv/year (1 mrem/year). This level of exposure was low enough to have a risk of <1 cancer/1,000,000 and the risk for lung cancer <1/10,000,000. The notation is negligible individual dose (NID) (Harley 2001, 2008). 

Average annual effective dose variation with altitude... 

This conclusion was reached on the basis that a diet made up entirely of locally produced food which would contain some amount of residual radionuclides could lead the hypothetical resettling population to be exposed to radiation from residual radionuclides in the island, mainly from Cs, resulting in annual effective dose levels of about 15 mSv (if the dose due to natural background radiation were added, this would result in an annual effective dose of about 17.4 mSv). This level was judged to require intervention of some kind for radiation protection purposes. 

---