1. Limitations in the assessment of radon dose:
the role of direct activity measurements
John Kalef-Ezra, Stratos Valakis
Medical Physics Laboratory, University of Ioannina

2. ANNUAL RADIATION BURDEN OF THE MEAN GREEK ADULT ~5 mSv
________________________________________
source ED source ED
natural (mSv) man made (mSv)_
cosmic radiation ~ plane radiographs
external spaces ~ fluoroscopy
internal spaces ~ interventional proc
internal radioactivity ~ scintigraphic exams
contamination due to CT examinations
radon and its progeny radiation workers ~ other sources ~0.2
total ~ ~2.3
GAEC, 2015
RISK
BENEFIT

3. INDOOR 222Rn CONCENTRATION AT UI/MPL (COLD PERIOD OF THE YEAR)
____________________________________ room floor CRn,air (Bq/m3)_ office # ground office # ground _ store room #1 ground store room #2 ground _____ lab room #1 1st floor lab room #2 1st floor lab room #3 ground (147/60) _ measurements by GAEC Mean 222Rn at the Ioannina University Campus buildings: floor: ground 105 Bq/m3, higher 63 Bq/m3 (Ioannides et al 2009)

4. EFFECTIVE DOSE DUE 222Rn INHALATION
ED = CRn,air x DF x F

5. vs

6. Ventilation rate (m3/h)
________________________________________ _________________________ _ ____
“average” adult male female ___
resting (sleeping)
sitting (awake)
light exercise
heavy exercise ___ ___
METABOLISM
uptake:
~ proportional to blood flow
retention, T1/2: * vs d
4.5 min (blood)
41 min (interstitial fluid)
3.4 h (intracellular fluid)
18 h (adipose tissue)
* Harley, Jetter, Nelson:
Environ Int 7: (1994)

7. THE LONG “JOURNEY” OF RADON PROGENY IN OUR BODY
nanoparticles
coarse particles

8. WHOLE BODY COUNTING OF A VOLUNTEER AT UIMPL
spectrum from
a single detector
0.242
214Pb
0.3
0.410
214Bi
0.609
40K
214Bi
1.46
1.76
226Ra Rn Po Pb Bi Po Pb
214Pb (T1/2 ~27 min), Eγ(keV): 242 (7.5%), 295 (19.2%), 352 (37%)
214Bi (T1/2 ~20min), Eγ(keV): 609 (46%), 1120 (15%), 1238 (6%), 1764 (16%)

9. WBC / IUMPL in vivo measurement
phantom measurement
in vivo measurement
WBC / IUMPL
Kalef-Ezra J, Valakis S, Soupsanas T: Radiation Protection Dosimetry 144: (2011)
Valakis S, Pallada S, Kalef-Ezra J: Health Physics 107: (2014)

10. TBBi (n=65) arithmetic mean: 115 Bq geometric mean: 101 Bq
Total body 214Βi in healthy volunteers
October to April, y, residing at <5 km from UIC
no recent: heavy exercise, heavy meal, smoking,…
___________________________________________________________________________________
TBBi (n=65)
arithmetic mean: Bq
geometric mean: Bq
standard deviation: Bq
coefficient of variation: 56% ____
lower TBBi in June than in April (n=14x2)
_________________________
TBBi: male>female
TBBi/BM: NS
_____________________________
age influence: NS
Kalef-Ezra, Valakis : Direct total body 214Bi…J. Radiological Protection (in press)

11. Total body 214Bi BODY COMPOSITION
________________________________________ group men (n=24) women (n=24) p__ age (y) (26) (28) BM (kg) (87) (63) < ΤΒΒi (Bq) (169) (79) FM (kg) (23.2) (22.5) FFM (kg) (63) (41) <0.001 % FM/BM (23.2) (36.0) ΤΒΒi/BM(Bq/kg) (1.78) (1.28) ΤΒΒi/FM(Bq/kg) (6.26) (3.94) ΤΒΒi/FFM(Bq/kg) (2.39) (1.98) _____________________________________________________________________ Kalef-Ezra J, Valakis S: J. Radiol. Protection (in press)

12. Whole body 214Bi activity in a adult volunteer following visits to A cave versus the time between exit from the cave and measurement
T½, eff
same cloths: (37+9) min
other cloths: (47+6) min
T½ (CoMo 170)
cloths – α: (39+2) min
53 Bq

13. Successive 214bi measurements
ΔT ~ 1.0 h, 22 male, 22 female
2nd TBBi< 1st TBBi (p<0.001)
mean 2nd TBBi/ 1st TBBi = 0.78
________________________________________________
Valakis et al, Proc. HNPS 2012

14. BISMUTH-214 SOURCES
226ra ingestion 222Rn ingestion 222Rn inhalation 218Po, 214Pb, 214Bi inhalation

15. MODELING OF 214Bi SOURCES
COLD PERIOD OF THE YEAR
_____________________________ source of 214Bi TBBi (Bq) ____________________women men median TBBi (cold period) _ 226ra ingestion Rn ingestion NS NS Rn inhalation Po/214Pb/214Bi inhalation ??_ ??_

16. RISK ASSESSMENT VIA
RADON MEASUREMENTS?
ED = CRn,air x DF x F

18. WHOLE BODY COUNTING 214Bi 40K 1.76
spectrum from
a single detector
0.242
214Pb
0.3
0.410
40K
214Bi
214Bi
0.609
1.46
1.76
226Ra Rn Po Pb Bi Po Pb
214Pb (T1/2 ~27 min) Eγ(keV): 242 (7.5%), 295 (19.2%), 352 (37%)
214Bi (T1/2 ~20min) Eγ(keV): 609 (46%), 1120 (15%), 1238 (6%), 1764 (16%)