risk assessment of radiation-induced thyroid cancer in population of belarus
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Risk Assessment of Radiation-Induced Thyroid Cancer in Population of Belarus. M.V.Malko Institute of Power National Academy of Sciences of Belarus, Minsk, Belarus. - PowerPoint PPT PresentationTRANSCRIPT
Risk Assessment of Radiation-Induced Thyroid
Cancer in Population of Belarus
M.V.MalkoInstitute of Power
National Academy of Sciences of Belarus, Minsk, Belarus
The incidence in thyroid cancer in the Belarusian population are presented in the report. It was found that approximately 8,700 additional thyroid cancers occurred in Belarus in 1990-2006 The number of thyroid cancers registered in Belarus in this period is about 13,300 cases (4,600 expected cases).
The relative risk averaged for this period is equal to 2.89 (95% CI from 2.80 to 2.99). The excessive absolute risk of thyroid cancer, EAR, averaged for the same period is assessed as 6.1 case per 104 PYSv (95% CI from 5.8 cases to 6.4 cases per 104 PYSv). The averaged excessive relative risk, ERR, is found equal to 22.7/Sv (95% CI from 21.5 to 23.9/Sv) and the averaged attributive risk, AR, is estimated equal to 65.4% (95% CI from 62.1 to 68.8%).
The mean deposition level of iodine isotope 131I on May 4, 1986 or one week after the accident at the Chernobyl Nuclear Power Plant was in some areas of the Gomel region higher than 37,000 kBq/m2. Recalculating with considering of the radioactive decay of this isotope gives the level of contamination higher than 74,000 kBq/m2. Such high levels of contamination with the isotope caused very high doses of the thyroid gland among the Belarusian population. They were by some children higher than 50 Gy (50,000 mGy). The collective equivalent dose of the thyroid gland irradiation of the Belarusian population is about 1,000,000 PGy (assessment of M.Malko).
It is well known that thyroid cancer is very rare disease by children. According to data of Prof. Demidchic (Belarus) only 21 case was registered among the Belarusian children (less than 15 years at the time of diagnose) in 1966-1985 or one case annually. This observed number of thyroid cancers in children corresponds to the number of person-years accumulated in the period 1966-1985 equal to 4.74·107. The last figure was assessed on the basis of demographic data given in handbooks of Belarus. Dividing the number of observed thyroid cancers among by this number of person-years gives the incidence rate of this cancers in children of Belarus equal to 0.443 cases per million persons-years.
Time-averaged crude and standardized (World standard) incidences in thyroid cancers in children.
Country Time Period Crude rate
Standardized rate
Sources
UK, England and Wales
1981-1990 0.6 0.5 IARC
UK, England and Scottish Cancer Register
1981-1990 0.6 0/5 IARC
Poland 1980-1989 0.5 0.5 IARC Slovakia 1980-1989 0.7 0.6 IARC Hungary 1985-1990 0.3 0.3 IARC Ukraine Before
Chernobyl accident
0.5 - Tronko et al
Belarus 1966-1985 0.44 - This report
Numbers of thyroid cancers registered in children of Belarus in 1986-2007
(Data of Prof. E.Demidchic)
0
10
20
30
40
50
60
70
80
90
100
1985 1990 1995 2000 2005 2010
Years
Nu
mb
ers
of
thyro
id c
an
cers
Incidence in thyroid cancers in children of Belarussian regions in 1986-2004. Regions Observed Expected O - E RR Brest 165 3 162 55 Vitebsk 11 2 9 5.5 Gomel 378 3 375 126 Grodno 43 2 41 21.5 city Minsk 62 3 59 20.7 region Minsk 42 3 39 14 Mogilev 43 2 41 21.5 Together 744 18 726 41.3
Fractions of children irradiated in 1986 as function of time
0
20
40
60
80
100
120
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
Years
Fra
ctio
n, %
0
2
4
6
8
10
12
14
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
Years
Inc
ide
nc
e i
n 1
00
,00
0
Incidence rates of thyroid cancer among irradiated children of Belarus.
Number of thyroid cancers registered in adolescents of Belarus in 1986-2006
(Data of Prof. E.P.Demidchic)
0
10
20
30
40
50
60
70
80
90
1985 1990 1995 2000 2005 2010
Years
Nu
mb
er
of
th
yro
id c
an
cers
Number of registered thyroid cancers in the cohort of persons that were at the age less than 19 years at the Chernobyl NPP (Kenigsberg et al)
0
50
100
150
200
250
1985 1990 1995 2000 2005
Years
Nu
mb
er
of
cases
Excessive relative risk (with 95%CI) of the incidence in thyroid cancer in Belarus in 1986-2002 in persons
irradiated at the age 0-18 years (ERR =34.3/Gy in 1991-2002).
-10
0
10
20
30
40
50
60
1985 1990 1995 2000 2005
Years
ER
R/1
Gy
Excessive absolute risk (with 95%CI) of the incidence in thyroid cancers in Belarus in 1986-2002 in persons
irradiated at the age 0-18 years (EAR =2.7/10000 PYGy)
-2
-1
0
1
2
3
4
5
1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004
Years
EA
R/1
0000
PY
Gy
Incidence rates in thyroid cancers in population of Belarus in 1986-2007
0
2
4
6
8
10
12
1985 1990 1995 2000 2005 2010
Years
Cas
es in
100
,000
per
son
s
Age specific incidence rates in thyroid cancer in Belarus in 1991-2006
0
5
10
15
20
25
30
Cases in
100,0
00 p
ers
on
s 1991 1995 2003 2006
Incidence rates of thyroid cancers in males of Latvia in 1985-2005 (IARC data)
y = 0.0215x - 41.787
R2 = 0.9146
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1980 1985 1990 1995 2000 2005
Year
Cases i
n 1
00,0
00 m
ale
s
Incidence rates in thyroid cancers in females of Latvia in 1985-2002 (IARC data)
y = 0.1019x - 199.08
R2 = 0.9217
3
3.5
4
4.5
5
5.5
1980 1985 1990 1995 2000 2005
Year
Cases in
100,0
00
Incidence rates of thyroid cancers in the mixed population of Latvia in 1985-2002 (IARC data)
y = 0.0646x - 126.08
R2 = 0.9166
1.5
2
2.5
3
3.5
4
4.5
1980 1985 1990 1995 2000 2005
Years
CA
SE
S in
100
,000
per
son
s
Comparison of incidence rates in thyroid cancers in males of Latvia and Belarus
0
1
2
3
4
5
1985 1990 1995 2000 2005 2010
Year
Cas
es in
100
,000
per
son
s
Latvia males Belarus males
Comparison of registered incidence rates in thyroid cancers in females of Latvia and Belarus
0
2
4
6
8
10
12
14
16
18
20
1980 1985 1990 1995 2000 2005 2010
Years
Cas
es in
100
,000
per
son
sLatvia females Belarus females
Comparison of incidence rates of thyroid cancers in populations of Latvia and Belarus
0
2
4
6
8
10
12
1985 1990 1995 2000 2005 2010
Years
Cas
es in
100
,000
per
son
s
Ряд1
Ряд2
÷ ÷
Comparison of radiation risks estimated for the Belarusian population and for atomic bomb survivors Belarus ATB* Period of time 1990-2006 1958-1998 Contingent Males Females Mixed Mixed PY 80,400,000 91,300,000 171,700,000 2,764,731 H(Coll), 104 PGy 44 104 50 104 104 PGy h(population), Gy 0.094 0.094 0.094 ~0.2 Duration of irradiation
2.6106 sec 2.6106 sec 2.6106 sec 2.6 sec
Dose rate, Gy/sec 0.036 10-6 0.036 10-6 0.036 10-6 0.1 Observed 1560 10,800 13,300 471 Expected 2500 3,660 4,600 408 O - E 940 7,140 8,700 63 RR 2.66 2.95 2.89 1.15 95% CI of RR 2.47 ÷ 2.87 2.83 ÷ 3.06 2.80 ÷ 2.99 EAR/104 PYGy, 2.3 9.3 6.1 1.2** 95% CI of EAR 2.1 ÷ 2.6 8.8 ÷ 9.9 5.8 ÷ 6.4 0.48 ÷ 2.2 ERR/Gy 19.9 23.3 22.6 0.57** 95% CI of EAR 17.6 22.4 22 ÷ 24.7 21.5 ÷ 23.7 0.24 ÷ 1.1 AR% 62.4 66.1 65.4 95% CI of AR,% 59.5 ÷ 65.1 62.1 ÷ 69.9 64.2 ÷ 66.6
* D.L/Preston, E.Ron, S.Tokukoko et al. Solid Cancer Incidence in Atomic Bomb Survivors: 1958 – 1998. Radiation Research, vol.168, pp.1-64 (2007). ** Estimates for atomic bomb survivors irradiated at the age 30 years and attained age 70 years.
CONCLUSIONS
1. The accident at the Chernobyl NPP caused in Belarus in 1990 – 2006 approximately 8,700 radiation-induced thyroid cancers.
2. Radiation risks of radiation-induced thyroid cancers caused in Belarus by the Chernobyl accident are by some factors higher than observed in atomic bomb survivors. 3. Radiation risks of thyroid cancers established for atomic bomb survivors (acute irradiation) are not relevant for irradiation of normal population. Using radiation risks observed for survived inhabitants of Hiroshima and Nagasaki underestimates real number of radiation-induced thyroid cancers in case of population exposed to chronic irradiation. 4. Using the Dose and Dose Rate Effectiveness Factor higher than 1 additionally underestimates number of radiation-induced thyroid cancers caused as a result of chronic irradiation of normal population.