Low doses of the ionizing radiation

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1 Low doses of the ionizing radiation mgr inż.. Krzysztof Wojciech Fornalski Dział Szkolenia i Doradztwa Instytut Problemów w Jądrowych, J Świerk krzysztof.fornalski@gmail.com Seminarium Doktoranckie 26 I 2010

2 Overview Low doses of ionizing radiation natural background The healthy worker effect Dose-effect effect relationships Perspectives Krzysztof W. Fornalski 2

3 Natural background of the ionizing radiation Krzysztof W. Fornalski 3

4 Krzysztof W. Fornalski 4

5 Annual dose in USA (2006) Consumption: Average annual dose: Cosmic ray others Ground radioactivity Medicine: In body Krzysztof W. Fornalski 5

6 Natural background in Poland Krzysztof W. Fornalski 6

7 Average annual dose in Poland 3,35 msv Natural sources: artificial sources (e.g. medicine): kkkkkkkkkkkkkkk Medicine, e.g. X-ray Chernobyl accident others Gamma ray Cosmic rays Body s radionuclides Krzysztof W. Fornalski 7 Source: PAA

8 Warszawa Krzysztof W. Fornalski 8

9 In Chernobyl closed zone Krzysztof W. Fornalski 9

10 Chernobyl s reactor 5 µsv/h Krzysztof W. Fornalski 10

11 Guarapari (Brazil) 27 µsv/h Krzysztof W. Fornalski 11

12 Ramsar (Iran) 126 µsv/h Krzysztof W. Fornalski 12

13 Radiation risk Major question: is this dose-rate harmful for those people? Medical answer: : NO There is no evidence for increase any risk in low dose region (<200 msv per year) Krzysztof W. Fornalski 13

14 What the radiation does? Gamma ray can destroy the DNA code There is ~20 DNA attacs in human body per one second from the natural radiation But ~ DNA attacs per second is caused by natural metabolism Even increasing the natural radiation by the factor of 100, it will be still a margin Krzysztof W. Fornalski 14

15 The healthy worker effect Mortalities from all causes and cancers are lower among nuclear industry workers from 15 countries 120 SMR = standard mortality ratio (observed to expected) SMR [%] Fornalski & Dobrzyński, 2010, Dose-Response 0 Fornalski & Dobrzyński, 2009, Int.. J. of Low Rad. controls nuclear workers Fornalski & Dobrzyński, 2009, Postępy Techniki Krzysztof Jądr W. dr. Fornalski 15 all causes cancers only

16 The healthy worker effect (HWE) The HWE is often offered as an only explanation for significantly lower standardized mortality ratios (SMR) among nuclear workers The HWE assumes better medical care and stricter medical requirements for nuclear workers than for others, resulting in healthier workers In theory, typical pre-employment employment health examinations may contribute to the HWE by eliminating not-fitted persons So new workers should be statistically healthier than people from the outside control population Krzysztof W. Fornalski 16

17 HWE and cancers Routine pre-employment employment medical examinations do not eliminate cancer-susceptible individuals, because e.g.. no genetic tests are carried out Also, early phase cancer cannot be detected via typical medical tests The notion of healthy worker effect does not apply when cancer deaths are considered: percentage of cancer deaths should be similar in both groups Thus it should be another explanation of lower cancer mortality among nuclear industry workers Krzysztof W. Fornalski 17

18 Radiation hormesis The concept of positive influence of low dose radiation (<200 msv) Mechanism, which repair DNA, can be stimulated by low radiation More DNA attacks, the more enzymes repairing damages are produced. The stimulation can produce a surplus of such enzymes. This mechanism can eliminate cancer and other defected cells Krzysztof W. Fornalski 18

19 Adaptive response - simple organism example High DUŻA DAWKA dose HODOWLA (breeding) Mutations, - Aberacje chromosomowe genetic - Mutacje nonstability, - Niestabilność genetyczna death of - Śmierć komórki many cells low MAŁA dose DAWKA HODOWLA (breeding) High dose DUŻA DAWKA HODOWLA (breeding) NO MUTATIONS NO CELL DEATHS Ww. zaburzenia nie występują lub są słabiej zaznaczone (M. Janiak et al.) Krzysztof W. Fornalski 19

20 Hormesis example Mice after 90 days (M. Janiak et al.) Krzysztof W. Fornalski 20

21 gamma ray in USA (on left) and cancer mortality (on right) Krzysztof W. Fornalski 21

22 Lung cancer risk Radon in American homes Krzysztof W. Fornalski 22 Radon concentration pci/l

23 Canadian lung cancers Krzysztof W. Fornalski 23

Cancer deaths per 100 000 citizens China study - HBRA = High Background Radiation

24 Cancer deaths per citizens China study - HBRA = High Background Radiation Area - CA = Control Area All population Between years old Krzysztof W. Fornalski 24

25 Hiroshima and Nagasaki Leukemias: Risk of cancer mortality Dose [msv] Dose [Sv] Krzysztof W. Fornalski 25

26 Dose-effect effect relationship In the high dose area (more than 0,5 Sv) the dose-effect effect relationship is linear (LNT Theory) In the low dose area (<0,2 Sv) is not linear (threshold? Hormetic?) Threshold model Linear model Dose Hormetic model Krzysztof W. Fornalski 26

27 Dose-effect effect relationship All studies are still searching the true dose-effect effect relationship It is certain that the relationship is not linear Biggest problems: statistics and confounding factors (e.g.. smoking, chemicals, hygiene etc.) Krzysztof W. Fornalski 27

28 Future studies Risk of lung cancer incidence Comprehensive studies of radon influence Completely incoherent results average annual dose rate [msv/y] Krzysztof W. Fornalski 28

29 Future studies Relative Growth Beta irradiation of crees (pol. rzeżucha jadalna) seeds Growth from seeds after 12 days 1,4 1,3 1,2 1,1 1 0,9 0,8 0,7 0, Krzysztof cumulative W. Fornalski dose of seeds (before growth) 29 [mgy]

30 Conclusions Dose - effect relationship is not linear In the low dose area (<200mSv) the response is rather hormetic (= beneficial for health) In the case of the nuclear industry workers the lower cancer mortality is not connected with the healthy worker effect Future studies in low dose area requires further work Krzysztof W. Fornalski 30

31 Thank you! Czarnobyl, 2008 Krzysztof W. Fornalski 31

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