Study on the radiation detriment

The cancer-specific mortality and incidence data of the Asian and Euro-American representative populations according to ICRP 103, tables A.4.10–A.4.17 [1] are used. The data are provided for all causes, all cancer and all solid cancer as well as for the solid cancer in the specific organs oesophagus, stomach, colon, liver, lung, female breast, ovary, bladder and thyroid. In addition, data are available for soft tissue cancer affecting the bone marrow (leukaemia).

According to the procedure of ICRP, the radiation-associated risks are calculated for incidence data using both the excess relative risk model and the excess absolute risk model (EAR). For solid cancers, the models involve a linear dose response allowing for modifying effects of sex, exposure age and attained age [1].

The bone marrow category includes leukaemia, excluding chronic lymphocytic leukaemia, and multiple myeloma [1]. In contrast to solid cancer, a linear-quadratic dose response is proposed for modelling the risks for bone marrow cancer [1, 8]. For this purpose, ICRP uses only the EAR model with effect modification by sex, age of exposure, and attained age [8].

Various risk quantities are proposed for estimating population risk:

• (a)  
  The excess lifetime risk (ELR) is the increase in the lifetime risk of developing the cancer of interest that an individual experiences as a result of exposure compared to the risk without exposure.
• (b)  
  The risk of exposure-induced cancer incidence (REIC) is the lifetime risk that a person will develop a cancer that has been caused by the exposure in question.
• (c)  
  The lifetime attributable risk (LAR) was proposed as approximation of REIC [9]. Unlike the REIC, the survival function included in the LAR does not account for radiation-induced effects.

In accordance with ICRP, the LAR is used in this study to estimate risks from radiation exposure. The REIC and ELR are also considered, but of these, only the REIC is further needed to determine the years of cancer-free life lost per radiation-induced cancer.

YLLRIC reflects the impact on the lives of affected individuals and expresses the average loss of cancer-free lifetime that a person suffers if cancer develops as a result of exposure during his or her lifetime. It is calculated as the ratio between the average loss of cancer-free lifetime for the population under consideration and the REIC.

According to ICRP, lifetimes and radiation risks are provided as averages across populations, sexes and ages. For this purpose, the representative populations specified by the ICRP are taken as hypothetical stationary populations.

In this study, the scenarios of acute and chronic exposure to low-LET radiation with a dose of 0.1 Gy and a constant dose rate of 0.1 Gy yr⁻¹, respectively, are considered. The dose value is consistent with the value used in another publication [4]. In ICRP 103, the dose value for which the calculations were undertaken is not reported.

In an acute exposure scenario, it is assumed that the organ or tissue under consideration is separately and instantaneously exposed to a dose from low-LET radiation (gamma radiation). The other organs or tissues are considered as not exposed. The same radiation dose is imposed on persons of all ages of the population under consideration. The radiation risks developed in the people are observed from the age of exposure up to the age of above 90 years.

The scenario assumed for chronic exposure is characterized by a constant dose rate imposed on each person starting at the age at which the person entries the population under consideration. The dose rate is maintained as long the person belongs to the population. For example, in a whole population, each person is exposed throughout life; in a working age population, the exposure occurs between the age 18 and 64 years. Likewise, in the case of chronic exposure, each organ or tissue considered is exposed individually, and the resulting radiation risks are observed even with premature cessation of exposure beyond the age of 90.

Figure 1 shows the scheme for the propagation of risks after acute exposure and for chronic exposure. For acute exposure, additional risks for cancer development occur in the years following the exposure. For chronic exposures, the risk at the attained age is the accumulation of each individual risk contribution caused by exposures in the past. The constant dose rate is simulated as successive acute single doses administered at intervals of equal duration of one year.

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It should be noted that the dose can be either the absorbed dose given in the unit Gy (Gray) or the dose equivalent given in the unit Sv (Sievert) for the radiation under consideration. The transformation between the two quantities is performed by the radiation weighting factor. For photons and other low-LET radiation, a radiation weighting factor of 1 Sv Gy⁻¹ has been established, making the absorbed dose value identical to the dose equivalent value in the organ under consideration. According to ICRP, in this study the risk quantities are related to the equivalent dose; the exposures are expressed as absorbed doses.

Population weighting of risks takes into account the age distribution of individuals in the population by weighting age-related risks according to the number of individuals in the corresponding age. This results in a risk measure that is used to quantify the health effects of radiation in the population under consideration.

The age distributions of persons in a non-exposed stationary population are calculated from equation (20) given in the supplementary material for this article. Figure 2 represents the normalized distributions of the different populations considered in this study.

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The distributions show that the risks due to exposures of persons aged under 65 contribute almost equally weighted. This applies to the whole population, to the working age population and even more so to the subpopulation under 18. Due to the increased mortality rate with increasing age, the age distribution shows a considerable decrease for ages of 65 and over.

In this study, the different populations are considered as self-contained groups composed of people in the specified age ranges. Table 1 shows the characteristic parameters of these populations. The average lifetime is the average time an individual belongs to this population when he/she reaches the entry age for this population. For the whole population, the average lifetime is the lifetime expected for the individual at birth.

The determination of the radiation detriment, ${\mathfrak{D}_{\text{c}}}$, for cancer c follows the approach of ICRP, as being

$$\begin{align}{\mathfrak{D}_{\text{c}}} = \left( {{R_{{\text{F,c}}}} + {q_{\text{c}}}{R_{{\text{NF,c}}}}} \right){ }{l_{{\text{R,c }}{\text{.}}}}\end{align} \tag{ 1 }$$

For a given cancer c, ${R_{{\text{F,c}}}}$ represents the fatal cancer risk, ${R_{{\text{NF,c}}}}$ is the non-fatal cancer risk, ${q_{\text{c}}}$ is a non-fatal weight reflecting the reduced quality of life associated with living with the cancer, and ${l_{{\text{R,c,s}}}}$ is the sex-specific relative life lost due to the cancer. When calculated with incidence data, the resulting risk includes the fatal and the non-fatal risk components, $\,{R_{\text{c}}} = {R_{{\text{F}},{\text{c}}}} + {R_{{\text{NF}},{\text{c}}}}$, with ${R_{{\text{F}},{\text{c}}}} = {k_{\text{c}}}{R_{\text{c}}}$ and ${R_{{\text{NF}},{\text{c}}}} = \left( {1 - {k_{\text{c}}}} \right){R_{\text{c}}}$. The coefficient ${k_{\text{c}}}$ is the lethality fraction of cancer c.

Since the population-averaged LAR, ${\overline {{\text{LAR}}} _{{\text{c}},{\text{s}}}}$, is used as relevant risk quantity to compute the radiation detriment for sex s and cancer c, it replaces ${R_{\text{c}}}$ and the radiation detriment is finally determined from

$$\begin{align}{\mathfrak{D}_{{\text{c}},{\text{s}}}} = { }{\overline {{\text{LAR}}} _{{\text{c}},{\text{s}}}}\left( {{k_{\text{c}}} + {q_{\text{c}}}\left( {1 - {k_{\text{c}}}} \right)} \right){ }{l_{{\text{R}},{\text{c}},{\text{s }}{\text{.}}}}\end{align} \tag{ 2 }$$

A detailed justification for the coefficients ${k_{\text{c}}}$ and ${q_{\text{c}}}$ is given by ICRP 103 [1]. It should be noted here that the coefficients depend only from the type of cancer c, but not on sex or dose. The values for the coefficients ${k_{\text{c}}}$ and ${q_{\text{c}}}$ are given in in table A.4.5 of ICRP 103 [1] and used without any modification.

The relative life lost is the ratio of the average years of cancer free life lost per radiation-induced cancer c, ${\overline {{\text{YLLRIC}}} _{{\text{c,s}}}}$, to the average years of life lost for all cancers,

$$\begin{align}{l_{R,{\text{c,s}}}} = { }\frac{{{{\overline {{\text{YLLRIC}}} }_{{\text{c,s}}}}}}{{{\text{av}}.{\text{ years of life lost all cancer}}}}.\end{align} \tag{ 3 }$$

In agreement with ICRP, the value of 15 years is used as the average years of life lost for all cancers. The value was derived from mortality data [10] and already used in ICRP 60 [2].

In the case of chronic exposures, the corresponding risks are given as risk per time interval and thus also detriment is given per time interval (usually per year),

$$\begin{align}{{\mathfrak{\dot D}_{{\text{c,s}}}}} = {{\dot{\overline {{\text{LAR}}} }_{{\text{c,s}}}}} \left( {{k_{\text{c}}} + {q_{\text{c}}}\left( {1 - {k_{\text{c}}}} \right)} \right)l_{R,{\text{c}},{\text{s }}{\text{.}}}^{\,{\text{ch}}}\end{align} \tag{ 4 }$$

The relative life lost, $l_{R,{\text{c}},{\text{s}}}^{\,{\text{ch}}}$ used in equation (4) is the ratio of the value of the average years of cancer free life lost per radiation-induced cancer, $\overline {{\text{YLLRIC}}} _{{\text{c,s}}}^{\,{\text{ch}}}$, given in equation (33) of the supplementary material for this article to the value of 15 years as the average years of life lost for all cancers according to ICRP.

The estimates of LAR and YLLRIC for organs and tissues calculated for acute exposure of the whole population and the working age population are presented in tables 2 or 3, respectively. For comparison purposes, the corresponding data from ICRP 103 [1] and those published in [5] are given. The ICRP data for the average years of life lost are calculated by multiplying the relative life lost of ICRP with the average of 15 years for the life lost of all cancers. Since the risk calculations for breast and ovaries can only be performed for females, averaging over the sexes sets the risks for men to zero. The corresponding values for YLLRIC are those calculated for females.

Table 2. Lifetime attributable risks (LAR) and average years of life lost per radiation induced cancer incidence (YLLRIC) for organs and tissues calculated for an acute exposure of the whole population with a dose to organ of 0.1 Gy; the corresponding data published in ICRP 103 and in [5] are given for comparison; the ICRP values for the average years of life lost for the given cancer are calculated by multiplying the relative years of life lost of ICRP 103 by the average years of life lost for all cancers of 15 years [2].

	This study: acute exposure with the single dose		ICRP 103 [1]		Pub. in [5]
Organ or tissue	${\overline {{\text{LAR}}} _c}$		Nominal risk coefficient	Average years of life lost years	Lifetime risk of cancer incid.
	cases per 10 000 persons per Sv	${\overline {{\text{YLLRIC}}} _{\text{c}}}$ years	cases per 10 000 persons per Sv		cases per 10 000 persons per Sv
Oesophagus	16.2	12.6	15.1	13.0	16
Stomach	81.2	13.3	79.1	13.2	79
Colon	69.2	13.1	65.4	14.5	66
Liver	31.3	13.5	30.3	13.2	31
Lung	124.5	11.8	114.2	12.0	108
Breast	95.4	14.3	112.1	19.4	97
Ovary	10.9	16.4	10.6	16.8	11
Bladder	47.5	10.8	43.4	10.6	41
Thyroid	29.1	16.5	32.5	19.4	19
Other solid	142.4	13.7	143.8	15.4	134
Bone marrow	66.5	26.5	41.9	24.4	63
Total	714.1	14.8 a	688.4	15.6 a	665

Deviations may occur due to rounding. ^a Mean value.

Table 3. Lifetime attributable risks (LAR) and average years of life lost per radiation induced cancer incidence (YLLRIC) for organs and tissues calculated for an acute exposure of the working age population with a dose to organ of 0.1 Gy; the corresponding data published in ICRP 103 are given for comparison; the ICRP values for the average years of life lost for the given cancer are calculated by multiplying the relative years of life lost of ICRP 103 by the average years of life lost for all cancers of 15 years [2].

	This study: acute exposure with the single dose		ICRP 103 [1]
Organ or tissue	${\overline {{\text{LAR}}} _{\text{c}}}$	${\overline {{\text{YLLRIC}}} _{\text{c}}}$ years	Nominal risk coefficient	Average years of life lost years
	cases per 10 000 persons per Sv		cases per 10 000 persons per Sv
Oesophagus	16.3	14.6	16	13.6
Stomach	71.2	15.1	60	13.4
Colon	62.3	14.8	50	17.0
Liver	27.6	15.4	21	14.0
Lung	143.6	13.5	127	14.4
Breast	62.1	16.5	49	18.0
Ovary	9.5	18.3	7	17.4
Bladder	46.5	12.2	42	12.8
Thyroid	10.2	18.5	9	17.8
Other solid	105.5	15.2	88	14.6
Bone marrow	73.2	27.8	23	17.6
Total	628.0	16.5 a	492	15.5 a

Deviations may occur due to rounding. ^a Mean value.

The calculated risks in the whole population for solid cancers other than lung and breast cancer show a slight increase of 4% on average compared to the ICRP values. The values published in [5] show a similar pattern, but with higher deviations for thyroid and the other solid cancer category. This study and the values published in [5] have in common that the highest deviations from the ICRP values are for lung, breast, and bone marrow. The values calculated for breast are lower in both studies, while the values for bone marrow are higher than the corresponding values of ICRP.

The LAR values for solid cancer in the working age population are invariably higher than those of the ICRP. Again, of note is the substantial discrepancy in the bone marrow values between this study and the ICRP.

The values for YLLRIC of the whole population are, on average, lower than those of the ICRP. In contrast, YLLRIC values for the working age population are higher. The highest YLLRIC is observed for bone marrow in both populations.

The reasons why the results of this study differ from the results published by the ICRP can be attributed to various causes:

• (a)  
  The development of risks is calculated in this study up to the age of above 90 years, while the ICRP states that calculations are only made up to an age of 85 years.
• (b)  
  The details of the calculation steps are not fully documented by ICRP and will differ in various studies, in particular

  • the way in which incidence data are included,
  • dealing with and averaging over age groups,
  • the way in which the population averaging for risks and life lost quantities is performed,
  • the different approaches used for the probability of surviving (see also [3, 6]),
  • the dose to organ, for which the calculations are carried out (in particular for bone marrow cancer).

Table 4 shows the risks quantities (ELR, REIC, LAR) and YLLRIC for bone marrow cancer depending on radiation doses and dose rates, and table 5 summarizes these quantities for solid cancers. Linearity of risk measures related to the dose at acute exposure is given when the dose-related risk values are constant for different doses. Accordingly, the same applies to chronic exposure.

Table 4. Values of ELR, REIC, LAR and YLLRIC for bone marrow calculated for different acute doses and chronic dose rates.

		Whole population				Working age population
Acute exposure	Dose Gy	${\overline {{\text{ELR}}} _{\text{c}}}$	${\overline {{\text{REIC}}} _{\text{c}}}$	${\overline {{\text{LAR}}} _{\text{c}}}$	${\overline {{\text{YLLRIC}}} _{\text{c}}}$	${\overline {{\text{ELR}}} _{\text{c}}}$	${\overline {{\text{REIC}}} _{\text{c}}}$	${\overline {{\text{LAR}}} _{\text{c}}}$	${\overline {{\text{YLLRIC}}} _{\text{c}}}$
		cases per 10 000 persons per Sv			years	cases per 10 000 persons per Sv			years
	0.01	61.8	62.1	62.1	26.5	68.1	68.4	68.4	27.8
	0.10	66.1	66.4	66.4	26.5	72.8	73.2	73.2	27.8
	1.00	108.9	109.5	110.2	26.5	120.1	120.6	121.5	27.8
Chronic exposure	Dose Rate Gy yr−1	$\mathop {{{\overline {{\text{ELR}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{REIC}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$	$\mathop {{{\overline {{\text{ELR}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{REIC}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$
		cases per 10 000 persons per year per Sv yr−1			years	cases per 10 000 persons per year per Sv yr−1			years
	0.01	62.5	62.8	62.8	33.7	68.5	68.8	68.8	26.5
	0.10	66.6	67.0	67.3	34.0	72.7	73.1	73.7	26.6
	1.00	103.7	104.2	111.6	39.4	106.4	106.9	122.3	29.0

Table 5. Total values of ELR, REIC, LAR and averaged values of YLLRIC for solid cancers calculated for different acute doses and chronic dose rates.

		Whole population				Working age population
Acute exposure	Dose Gy	${\overline {{\text{ELR}}} _{\text{c}}}$	${\overline {{\text{REIC}}} _{\text{c}}}$	${\overline {{\text{LAR}}} _{\text{c}}}$	${\overline {{\text{YLLRIC}}} _{\text{c}}}$	${\overline {{\text{ELR}}} _{\text{c}}}$	${\overline {{\text{REIC}}} _{\text{c}}}$	${\overline {{\text{LAR}}} _{\text{c}}}$	${\overline {{\text{YLLRIC}}} _{\text{c}}}$
		cases per 10 000 persons per Sv			years	cases per 10 000 persons per Sv			years
	0.01	617.9	647.6	647.7	13.6	531.2	554.9	554.9	15.4
	0.10	617.2	646.9	647.7	13.6	530.8	554.5	554.9	15.4
	1.00	610.6	640.0	647.7	13.6	527.2	550.7	554.9	15.4
Chronic exposure	Dose Rate Gy yr−1	$\mathop {{{\overline {{\text{ELR}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{REIC}}} }_{\text{c}}}}\limits^{\text{.}}$	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$	$\mathop {{{\overline {{\text{ELR}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{REIC}}} }_{\text{c}}}}\limits^.$	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$
		cases per 10 000 persons per y per Sv yr−1			years	cases per 10 000 persons per y per Sv yr−1			years
	0.01	619.6	649.4	652.0	17.6	532.3	556.1	557.6	16.5
	0.10	597.9	626.9	652.0	17.8	519.4	542.7	557.6	16.6
	1.00	444.1	466.6	652.0	19.9	419.2	438.7	557.6	17.5

Values for ELR, REIC and LAR are the sums for oesophagus, stomach, colon, liver, lung, breast, ovary, bladder, thyroid and the other solid category.Values for YLLRIC are the averages for oesophagus, stomach, colon, liver, lung, breast, ovary, bladder, thyroid and the other solid category.

Based on the linear-quadratic risk model, the dose-related risks for bone marrow cancer show a pronounced dose dependence that increases with dose. At the same dose, the values for the risks ELR, REIC and LAR do not differ significantly from each other. No significant variations are observed for the YLLRIC. In the case of chronic exposure, the differences between the various risk quantities are greater. The YLLRIC value increases with increasing dose rate, but this is only relevant for doses above 0.1 Gy yr⁻¹.

For solid cancers, the independence of LAR from dose is confirmed. ELR and REIC show little dependence on dose, which is due to the survival function that incorporates radiation-induced effects. These effects are negligible in the low dose range below 0.1 Gy, where ELR and REIC can also be considered as dose-linear quantities. At high doses, the number of people affected by radiation increases, but the probability of survival decreases more rapidly, resulting in a decrease in ELR and REIC per dose. No significant changes with dose are also observed for YLLRIC in solid cancers. For chronic exposure, the differences between the various risk measures are substantial. YLLRIC likewise increases with increasing dose rate.

From the LAR and the YLLRIC values in tables 2 and 3, respectively, the organ-specific radiation detriments are calculated for acute exposure of the whole population and the working age population according to equation (2). The detriments are presented in table 6.

If the values for breast and bone marrow are disregarded, the total radiation detriment as the sum of the organ-specific detriments for the whole population shows a good agreement with the corresponding values of ICRP and the values published in [4]. A somewhat different picture emerges for the working age population. Here, the calculated values for radiation detriment are systematically higher than those of ICRP, which is the only basis for comparison in this case. The largest difference occurs for bone marrow cancer, while the values for breast cancer show good agreement.

Whole-body exposure affects all organs and tissues and increases the likelihood of developing cancer in different parts of the body at the same time. This leads to a considerable shortening of life due not only to the cancer under consideration, but also to the radiation-related effects on other organs or tissues of the body. Because of this cross-interference with other sites, the whole-body exposure approach underestimates the lifetime risk of developing cancer in a particular organ or tissue.

The calculations in this study are performed assuming that each organ or tissue is exposed separately. The survival function used for ELR, REIC, and loss of life only accounts for the radiation effects on the rates for the cancer under consideration. However, the risk quantities are dose-dependent: as the radiation dose increases, the lifetime risk of solid cancers increases less (table 5). The application of LAR finally overcomes this effect as well and further simplifies the calculation. Using the survival function without accounting for radiation effects implies that at higher doses where there is substantial life shortening, LAR is somewhat larger than the actual number of attributable cancer incidence [9]. This results in a slight difference between LAR and REIC, but this is of little or no practical concern. In linear dose response models, as is the case for all solid cancers, LAR increases linearly with dose.

In order to compensate for the differences in the various risk quantities and also to minimize dose and dose rate effects associated with bone marrow, it is suggested that the concept of radiation detriment be applied only in the range of low doses below 0.1 Gy or dose rates below 0.1 Gy yr⁻¹. Within the low dose range most exposure situations occur and stochastic radiation effects are predominant.

The decision to use LAR as the relevant risk quantity allows the total radiation detriment to be represented as a linear combination of detriments to individual organs and tissues, which is also consistent with the concept of effective dose.

Table 6 provides a total detriment of approx. 5.5 × 10⁻² Sv⁻¹ for the whole population, and about 5.6 × 10⁻² Sv⁻¹ for the working age population, respectively, determined from the calculations of individual radiation detriment for ten organs and the bone marrow tissue. It should be taken into consideration that these values do not include the contributions of skin, bone, gonads (heritable), which ICRP additionally reports as 0.34 × 10⁻² Sv⁻¹ for the whole population, and 0.21 × 10⁻² Sv⁻¹ for the working age population [1]. The total radiation detriment over organs and tissues in this study is consistent with the nominal detriment (detrimental adjusted nominal risk coefficient) of 5.7 × 10⁻² Sv⁻¹ for the whole population from ICRP 103. However, the total radiation detriment for the working age population is about the same as for the whole population, and thus significantly higher than the corresponding nominal detriment of 4.2 × 10⁻² Sv⁻¹ from ICRP 103.

Both the working age population and the other subpopulations used in this study are considered self-contained. The working age population includes only people between the ages of 18 and 64 who are collectively exposed to acute radiation dose. The emerging risks are observed up to an age of more than 90 years. Comparable detriments for the whole population and the working age population result from the age dependence of the risks: The higher risks due to exposure of younger persons in the whole population are compensated by the lower risks of older persons.

It should be noted that there are also alternative scenarios possible:

• (a)  
  A whole population is exposed between 18 and 64 years of age, while exposures in other ages do not occur. In this case, the risks calculated in this study for the working age population should be projected to the whole population. The risks would be reduced to about 58%, which is the ratio of the lifetime of working age individuals to that of the whole population as shown in table 1.
• (b)  
  An adult population consisting of persons of the whole population who have attained the age of 18 years is exposed between age 18 and 64. The risks for this scenario are obtained from the risks calculated in this study for the working age population, reduced to about 74%. The reduction results from the ratio of the lifetime of working age individuals according to table 1 to that of the adult population, which consists of persons aged 18 and over (average lifetime 61.6 years).

In the alternative scenarios, the respective total radiation detriment is also reduced accordingly, which could explain the lower detriment of ICRP for the working age population. From the point of view of this study, the alternatives discussed above underestimate the risks and thus the radiation exposure for occupationally exposed persons. This underestimation results from averaging over parts of the population not affected by radiation exposures. In contrast, the approach used in this study for the working age population and the other subpopulations considers only those exposed to radiation.

Average risks and detriments for acute and chronic exposure are given in tables 7 or 8, respectively, for the whole population and for different subpopulations: People in childhood and adolescence (under 18 years of age), the working age population (18–64 years of age), and people of advanced age 65 and over. The respective age distributions from figure 2 were used for the population averaging.

Table 7. Average LAR, YLLRIC and detriments for organs and tissues calculated for acute exposure of different parts of the population with a dose of 0.1 Gy.

Whole population, dose 0.1 Gy
Age at exposure	Under 18 years			From 18 to 64 years (working age population)			From 65 years			Whole population
Organs and tissues	${\overline {{\text{LAR}}} _{\text{c}}}$			${\overline {{\text{LAR}}} _{\text{c}}}$			${\overline {{\text{LAR}}} _{\text{c}}}$			${\overline {{\text{LAR}}} _{\text{c}}}$
	cases per 10 000 persons per Sv	${\overline {{\text{YLLRIC}}} _{\text{c}}}$ years	${\mathfrak{D}_{\text{c}}}$ 10−4 per Sv	cases per 10 000 persons per Sv	${\overline {{\text{YLLRIC}}} _{\text{c}}}$ years	${\mathfrak{D}_{\text{c}}}$ 10−4 per Sv	cases per 10 000 persons per Sv	${\overline {{\text{YLLRIC}}} _{\text{c}}}$ years	${\mathfrak{D}_{\text{c}}}$ 10−4 per Sv	cases per 10 000 persons per Sv	${\overline {{\text{YLLRIC}}} _{\text{c}}}$ years	${\mathfrak{D}_{\text{c}}}$ 10−4 per Sv
Oesophagus	17.5	16.4	19.0	16.3	14.6	15.7	14.0	6.5	6.0	16.2	12.6	13.5
Stomach	169.2	18.9	207.6	71.2	15.1	70.0	10.8	6.4	4.5	81.2	13.3	70.4
Colon	135.1	18.1	123.7	62.3	14.8	46.7	10.2	6.5	3.3	69.2	13.1	45.6
Liver	63.9	19.0	81.0	27.6	15.4	28.4	3.7	6.5	1.6	31.3	13.5	28.1
Lung	126.5	15.0	125.1	143.6	13.5	127.8	69.8	6.5	29.7	124.5	11.8	97.3
Breast	267.6	19.1	185.7	62.1	16.5	37.3	3.2	7.1	0.8	95.4	14.3	49.5
Ovary	24.3	25.0	33.8	9.5	18.3	9.7	1.1	7.2	0.4	10.9	16.4	9.9
Bladder	79.0	13.8	39.7	46.5	12.2	20.6	13.7	6.3	3.1	47.5	10.8	18.7
Thyroid	105.0	25.8	55.6	10.2	18.5	3.9	0.1	6.7	0.0	29.1	16.5	9.9
Other solid	340.3	20.6	357.1	105.5	15.2	81.6	11.2	6.4	3.7	142.4	13.7	99.2
Bone marrow	82.4	58.7	290.6	73.2	27.8	122.1	28.2	7.0	12.0	66.4	26.5	106.0
Total	1410.8	22.8 a	1518.9	628.0	16.5 a	563.8	166.0	6.6 a	65.1	714.1	14.8 a	548.1

Deviations may occur due to rounding. ^a Mean value.

Table 8. Average LAR, YLLRIC and detriments for organs and tissues calculated for chronic exposure over different ages with a constant dose rate of 0.1 Gy yr⁻¹.

Whole population, dose rate 0.1 Gy yr−1
Age at exposure	Under 18 years			From 18 to 64 years (working ages)			From 65 years			Throughout life
Organs and tissues	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$ years	${{\dot {\mathfrak{D}_{\text{c}}}}}$ 10−4 per year per Sv yr−1	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$ years	${{\dot {\mathfrak{D}_{\text{c}}}}}$ 10−4 per year per Sv yr−1	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$ years	${{\dot {\mathfrak{D}_{\text{c}}}}}$ 10−4 per year per Sv yr−1	$\mathop {{{\overline {{\text{LAR}}} }_{\text{c}}}}\limits^.$	$\overline {{\text{YLLRIC}}} _{\text{c}}^{\,{\text{ch}}}$ years	${{\dot {\mathfrak{D}_{\text{c}}}}}$ 10−4 per year per Sv yr−1
	cases per 10 000 persons per year per Sv yr−1			cases per 10 000 persons per year per Sv yr−1			cases per 10 000 persons per year per Sv yr−1			cases per 10 000 persons per year per Sv yr−1
Oesophagus	17.5	16.4	19.0	16.4	14.4	15.7	15.3	7.1	7.2	16.5	13.6	14.9
Stomach	169.4	19.1	209.5	71.8	16.3	76.2	11.6	7.5	5.6	81.6	17.5	93.0
Colon	135.3	18.2	123.9	62.7	15.7	49.8	11.1	7.6	4.3	69.6	16.7	58.5
Liver	64.0	19.1	81.1	27.7	16.4	30.1	4.0	7.7	2.0	31.5	17.5	36.8
Lung	126.6	15.0	125.2	144.6	13.6	130.2	75.6	7.4	36.6	126.3	13.4	111.2
Breast	267.9	19.5	190.3	62.8	18.1	41.5	3.4	8.5	1.1	95.6	19.2	66.9
Ovary	24.3	25.3	34.2	9.6	20.0	10.6	1.1	8.4	0.5	11.0	22.4	13.7
Bladder	79.1	13.9	40.2	46.8	12.5	21.2	14.9	7.1	3.8	47.9	12.8	22.2
Thyroid	105.2	26.1	56.4	10.2	22.5	4.7	0.1	8.3	0.0	29.1	25.4	15.2
Other solid	340.8	21.2	368.0	106.6	16.7	90.6	12.1	7.5	4.6	143.0	19.3	141.3
Bone marrow	82.5	59.5	295.4	73.7	26.6	117.7	31.0	8.5	15.9	67.3	34.0	137.8
Total	1412.6	23.0 a	1543.2	632.9	17.5 a	588.3	180.2	7.8 a	81.6	719.4	19.3 a	711.5

Deviations may occur due to rounding. ^a Mean value.

From the first view, good agreement of the exposure-related risk quantities is obtained for acute and chronic exposure. However, the interpretation of the results is different:

• (a)  
  In an acute exposure situation, the population is instantaneously exposed to radiation dose. The risks are observed for the remaining lifetime of the people belonging to this population and are a measure of the adverse effects that will develop in the future. The risks are given in the unit per dose.
• (b)  
  In the case of chronic exposure, the population has been continuously exposed to a dose rate in the past. The risks measure the adverse effects to which the individuals are subjected at the time of observation. The risks are given in the unit per year per dose rate. The unit indicates the cases that occur in an observation period of one year.

The good agreement of the values obtained for acute and chronic exposure confirm the theoretical considerations [7] and support the confidence in the methodology developed in this study for the determination of radiation risks.

A closer look at the results shows that YLLRIC is generally higher for chronic exposure than for acute exposure. While the increase for the subpopulations is small or moderate, the YLLRIC for the whole population is on average about 30% higher.

The difference in YLLRIC for acute and chronic exposure can be attributed to the different exposure scenarios. When an acute exposure occurs, the person has no risks from previous exposures. For chronic exposures, the risk at the attained age is the accumulation over those caused by previous exposures. Risk burden from previous exposures, already present at this age, may lead to earlier cancer development with chronic exposure. The longer the population is exposed to radiation, the stronger the effect. For a whole population, where individuals are exposed to radiation throughout their lives, cancer could occur earlier in life, leading to an increase in YLLRIC.

Looking at individual cancers sites, the oesophagus, lung, and bladder show the smallest differences in YLLRIC between acute and chronic exposure of the whole population. Cancer develops at these sites at advanced ages. Exposures at young ages do not strongly affect the YLLRIC value.

The increased YLLRIC for chronic exposures is transferred to the radiation detriments and results in an approx. 30% higher value for the whole population on average and a slight increase for the subpopulations.

Tables 7 and 8 reveal the age dependence of risks and detriments. As expected, the highest detriments are associated with exposures during childhood and adolescence. Since these values are population-averaged, children under 5 years of age are attributed even higher detriment than those reported in the tables. A total detriment of about 0.19 per Sv is calculated for children under 5 years of age. The lowest risks and detriments are attributed to people in age 65 and over. Within the whole population, the total detriment imposed on people varies by a factor of about 30. The average values provided by ICRP for the whole population mask these variations and underestimate radiation risks in childhood and adolescence by a factor of more than three. Since the detriments are the basis for establishing the effective dose, this leads to a similar underestimation of the effective dose for people in these age groups.

It should be noted that unlike other cancer sites, the lung is an exception: The risks are not significantly increased for exposures in childhood and adolescence compared to the whole population. In contrast to other cancers, the risk of lung cancer is even higher for exposures in the working age population than for exposures at younger ages.

Figures 3 and 4 shows the LAR and the YLLRIC for acute exposure of the whole population and the working age population depending on age of exposure. The figures contain information for the selected organs: bladder, thyroid, lung and bone marrow. The LAR is given unweighted and weighted using the weights presented in figure 1. The sum of the weighted LAR across the ages at exposure gives the population-averaged LAR. The resulting YLLRIC is the unweighted average across the ages at exposure.

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4.4.1. Bladder

4.4.2. Thyroid

4.4.3. Lung

4.4.4. Bone marrow