nuclear and radiation science muic 2015 student presentation nuclear and radiochemistry undergraduate course copyright belongs to the author

1. The world’s high background
natural radiation areas
By
Pakpong Roongruangsree
5480978

2. HBNRAs
• High Background Natural Radiation Areas
• The paper reviews issues
• Dosimetric : measurement of absorbed dose
• Epidemiological : causes of diseases
• Radiological : emission of energy in waves
• Failures to report any increase in cancer incidence
• Validity of linear no-threshold hypotheses

3. Background radiation
• 80% of annual effective dose comes from background natural
radiation
• Radon produce large proportion of radiation in man’s environment
• HBNRAs residents receive more radiation than Normal background
radiation areas (NBRAs)
• Inhabitants’ annual effective dose (He) : tissue weighted sum of health
effects of low levels of radiation in body
• Low: He = 5 mSv per year medium: He = 5-10 mSv per year
• high He = 20-50 mSv per year very high: He > 50 mSv per year

4. Linear no-threshold (LNT)
• Epidemiological studies fails to report
the increase in cancer in HBNRAs
• LNT is a model assuming that biological
damage is proportional to effective dose
of radiation in long term

5. Yangjiang (China)
• Yangjiang, Guangdong province with 5 generations of people
• Natural external radiation : Monazite containing Th-232, U-238,K-4
• He = 4.27 mSv per year
• Health survey spans 20 years
• Thyroid nodularity in 50-56 years old female
• Cumulative dose 2 fold higher than NBRAs
• Thyroid incidence is higher in HBNRA
but may be from low iodine consumption

6. Yangjiang (China)
• Radiation may cause chromosomal diseases
• Dicentric and ring chromosomal aberrations
• But no significant increase in frequency
• Cancer-related mortality
• Leukemia, breast cancer, lung cancer : not higher
than NBRAs
• Non-leukemia cancer : 14.6 % lower than NBRAs
• Adaptive response for lymphocyte
• High incidence of Down’s syndrome :
may be from age of maternity

8. Kerala, Tamil and Orissa coasts (India)
• Monazite and heavy minerals : ilmenite, rutile, zircon, garnet
• Orissa He = 0.78-3.86 mSv per year
• Kerala He = 0.5-15 mSv per year
• No significant difference in fertility index, sex ratio, infant mortality
• High incidence of mental retardation
• But no difference in chromosomal aberration in newborns in cord blood
samples
• Negative correlation between Telomere length and age
• Radiation has no effects on telomere length
• No relation to malignant tumor

10. Poços de Caldas, Arax’a, Tapira (Brazil)
• Volcanic alkaline, monazite sand abundant
• High radium concentration in coastal lagoon in Rio de Janeiro
• He = 3.5-10 mSv per year
• Cancer mortality in 10 years is lower than expected (Arax’a)
• With confounders ( not relate to radiation)
• Guarapari beach sand Ra activity: 200 times higher than Organization
for Economic Co-operation and development (OECD) limits
• Increase in chromosomal aberration in HBNRA

11. Ramsar (Iran)
• Hot springs brings up Ra-226 and its decay products (9 as spas)
• Bedrock contains Uranium, decay to Ra
• He = 0.6-131 mSv per year (mean = 6 mSv)
• Ra-226 substitutes for Ca, RaCO3
(used as building materials)
• External and Internal He = 3.0-202 mSv per year
• In 50 years He = 10.1 Sv
( 10 folds 50 years limit of 1 Sv for workers)
• Chromosomal aberration in cells show significant positive results
• Tumor biomarkers in blood in Ramsar : significant correlations between
chronic exposure and tumor markers

12. • Higher cancer mortality in females who remains indoor compare to NBRA
• Later studies : Adaptive response also presents as well
• Reduce frequency of chromosomal aberration in HBNRA residents
• Resistance to high radiation doses
• No significant difference in males
• Negative correlation in lung cancer
• Continuous exposure may trigger anti oxidant and repair enzyme
production
• Ramsar has much less residents than Yangjiang and Kerala
• Small study cases
• Difficult to collect observation
Ramsar (Iran)

14. Discussion
• Most of the studies conclude with no links between exposure and
cancer mortality
• Confounders also interfere in methodology such as maternal age etc.
• Robust statistic is needed
• Resistant against errors
• Deviation from assumptions
• Chromosomal aberration is a reliable biodosimetric tool
• Yet it shows no evidence for correlation with effective dose
• Validity of Linear no-threshold (LNT) is questioned
• Beneficial effect of exposure to radiation is shown by adaptive effect

15. Discussion
• High concentration of Ra gas
• Lung cancer could be from the indoor radon gas rather than outdoor
• Lack of evidence yet again
• Radon barrier : the most effective way too reduce it effect
• Plastic and rubber damp proof sheets
(polyethylene)

16. References
• Abubakar, S. A.; Ahmad, T. R. The world’s high background netural
radiation areas (HBNRAs) revisited: A broad overview of the
dosimetric, epidemiological and radiobiological issues. Radiat.
Meas. 2015, 73, 51-59.
• Princeton University.
http://web.princeton.edu/sites/ehs/osradtraining/biologicaleffects/Ri
sk.htm/ (accessed March 18, 2015).
• Visqueen Radon Membrane CE Mark to EN 13967 ; Visqueen building
product : London, 2014; Visqueen Radon Membrane EN 13967 Type
A.