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

ANNUAL RADIATION BURDEN OF THE MEAN GREEK ADULT ~5 mSv ________________________________________ source ED source ED natural (mSv) man made (mSv)_ cosmic radiation ~0.3 plane radiographs 0.10 external spaces ~0.1 fluoroscopy 0.01 internal spaces ~0.5 interventional proc. 0.13 internal radioactivity ~0.2 scintigraphic exams 0.11 contamination due to CT examinations 1.47 radon and its progeny 1.7 radiation workers ~0.3 other sources ~0.2 total ~2.7 ~2.3 GAEC, 2015 RISK BENEFIT

INDOOR 222Rn CONCENTRATION AT UI/MPL (COLD PERIOD OF THE YEAR) ____________________________________ room floor CRn,air (Bq/m3)_ office #1 ground 62 office #2 ground 109 _ store room #1 ground 133 store room #2 ground 198 _____ lab room #1 1st floor 62 lab room #2 1st floor 112 lab room #3 ground 340 (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)

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

vs

Ventilation rate (m3/h) ________________________________________ _________________________ _ ____ “average” adult male female ___ resting (sleeping) 0.45 0.32 sitting (awake) 0.54 0.39 light exercise 1.5 1.3 heavy exercise 3.0 2.7 ___ ___ METABOLISM uptake: ~ proportional to blood flow retention, T1/2: * vs 3.82 d 4.5 min (blood) 41 min (interstitial fluid) 3.4 h (intracellular fluid) 18 h (adipose tissue) * Harley, Jetter, Nelson: Environ Int 7: 573-84 (1994)

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

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 222Rn 218Po 214Pb 214Bi 214Po 210Pb 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%)

WBC / IUMPL in vivo measurement phantom measurement in vivo measurement WBC / IUMPL Kalef-Ezra J, Valakis S, Soupsanas T: Radiation Protection Dosimetry 144: 415-418 (2011) Valakis S, Pallada S, Kalef-Ezra J: Health Physics 107: 36-46 (2014)

TBBi (n=65) arithmetic mean: 115 Bq geometric mean: 101 Bq Total body 214Βi in healthy volunteers October to April, 20-65 y, residing at <5 km from UIC no recent: heavy exercise, heavy meal, smoking,… ___________________________________________________________________________________ TBBi (n=65) arithmetic mean: 115 Bq geometric mean: 101 Bq standard deviation: 99 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)

Total body 214Bi BODY COMPOSITION ________________________________________ group men (n=24) women (n=24) p__ age (y) 34.5+16.5 (26) 34.3+15.4 (28) 0.96 BM (kg) 85 + 11 (87) 66 + 14 (63) <0.001 ΤΒΒi (Bq) 153+62 (169) 97 + 61 (79) 0.003 FM (kg) 23.3+ 8.6(23.2) 23.3+ 8.7(22.5) 0.68 FFM (kg) 61.9 + 7.7 (63) 42.7+ 6.6 (41) <0.001 % FM/BM 26.8+7.8(23.2) 34.4+6.7(36.0) 0.001 ΤΒΒi/BM(Bq/kg) 1.84+0.91(1.78) 1.49+0.91(1.28) 0.19 ΤΒΒi/FM(Bq/kg) 7.95+5.89(6.26) 4.51+2.93(3.94) 0.014 ΤΒΒi/FFM(Bq/kg) 2.52+1.17(2.39) 2.31+0.98(1.98) 0.56 _____________________________________________________________________ Kalef-Ezra J, Valakis S: J. Radiol. Protection (in press)

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

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

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

MODELING OF 214Bi SOURCES COLD PERIOD OF THE YEAR _____________________________ source of 214Bi TBBi (Bq) ____________________women men median TBBi (cold period) 97 153_ 226ra ingestion 0.2 0.3 222Rn ingestion NS NS 222Rn inhalation 7 6.5 218Po/214Pb/214Bi inhalation ??_ ??_

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

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 222Rn 218Po 214Pb 214Bi 214Po 210Pb 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%)