NUKLEONIKA 2012;57(3):411 420 ORIGINAL PAPER Studies of the rdon progeny prticle size distributions in the domestic environment. Epidemiologicl nd dosimetric dose estimtes Klin Mmont-Cieśl, Olg Stwrz Abstrct. Mesurements of the short-lived rdon progeny prticle size distributions were performed under relistic nturl conditions in 54 dwellings in 6 regions of Polnd by mens of the Rdon Progeny Prticle Size Spectrometer (RPPSS). The RPPSS comprises one open fce stge, 4-stge diffusion bttery nd 3-stge multi-hole inertil impctor. It ws mnufctured t the ARPNSA (Melbourne, Austrli), under supervision of Dr S. B. Solomon nd supplied with his softwre. While using the continuous mode, the progrmme provides nlysis of the potentil lph energy concentrtion on ech stge, prticle size distributions nd weighted dose conversion fctors bsed on the ICRP humn respirtory trct model (HRTM) s implemented in the computer code RADEP (rdon dose evlution progrm). The unttched frction indoors rnges from c. 0 to 53% with n rithmetic men nd medin of 17%. The equilibrium fctor F ws observed in the rnge from 7 to 64% with n rithmetic men of 32% nd medin of 29%. The nnul effective doses from rdon progeny for the generl popultion were estimted ccording to two models: epidemiologicl nd dosimetric. The men vlues of the rtios of the dosimetric to epidemiologicl dose estimtes for the generl popultion (brething rte 0.78 m 3 /h) nd workers (brething rte 1.2 m 3 /h) re 1.0 nd 1.4, respectively. The epidemiologicl dose estimtes for the generl popultion re smller in comprison with the dosimetric estimtes for the unttched frction f p greter thn 17%. It ws shown tht the dependence of the rtio of the doses estimted on the bsis of two models on the unttched frction f p is well described by liner eqution. Key words: rdon progeny prticle size distribution (RPPSD) weighted dose conversion fctors dosimetric/epidemiologicl effective dose estimte conversion convention unttched frction (f p ) rdon dose evlution progrm (RADEP) Introduction K. Mmont-Cieśl, O. Stwrz Centrl Lbortory for Rdiologicl Protection, 7 Konwliow Str., 03-194 Wrsw, Polnd, Tel.: +48 22 814 0159, Fx: +48 22 811 1616, E-mil: klinm@clor.ww.pl Received: 5 Mrch 2012 Accepted: 12 June 2012 Atoms of the rdon dughters immeditely fter the rdioctive decy of rdon toms hve tendency to ttch to condenstion nuclei producing rdioctive erosols. Aerosols of size below 10 nm, composed of unttched ions or neutrl toms nd moleculr clusters ssocited with rdon progeny toms, re trditionlly clled unttched frction. Aerosols bove 10 nm up to greter thn 1000 nm, with predominnt size between 50 nd 500 nm, re clled ttched frction. It is estimted tht equivlent dose to the lung from rdon gs is only bout one hundredth of tht from its short-lived dughters which constitute the min helth hzrd to the humn respirtory trct in the rdon environment. The effective dose, mesure of this hzrd, is clculted s product of the potentil lph energy concentrtion (PAEC) in the ir nd dose conversion fctor (DCF) or dose per unit intke. There re two pproches to the estimtion of DCF. One of them, recommended by the Interntionl Rdition Protection Committee Publiction 65 [5] introduces
412 K. Mmont-Cieśl, O. Stwrz two single conversion fctors, clled rdon progeny conversion convention, 1425 msv/(j h/m 3 ) for the occuptionl hzrd nd 1100 msv/(j h/m 3 ) for the generl popultion. The conversion fctors re determined from the epidemiologicl studies of urnium miners. A second, biokinetic nd dosimetric pproch is bsed on the ICRP Publiction 66 [6] which strongly recommends the usge of the humn respirtory trct model (HRTM) for inhltion of irborne rdionuclides. The dosimetric models revel tht the dose per the unit of intke of rdon progeny depends on the rdon progeny erosol chrcteristics, in prticulr, on the size nd frction of the ultrfine toms nd clusters (unttched frction) nd the physiologicl prmeters such s the brething rte. The site of the erosol deposition in the respirtory trct strongly depends on the prticle size distribution. Becuse diffusion is the dominting mechnism of the erosol deposition in the lung, the most diffusive frction, mostly the first rdon progeny 218 Po, constitutes the biggest cncer risk. Therefore, it is prticulrly importnt for the estimtion of the rdon effective dose to mesure the prticle size distribution. The dosimetric pproch uses the weighted dose conversion fctor which combines the rdon progeny size distribution in prticulr exposure loction with the prticle-size dependent dose conversion fctors derived from ICRP Publiction 66. The dosimetric models dopt the ssigned frction of the tissue weighting fctor w T for the lung nd the rdition weighting fctor w R for lph rdition. Some uthors [13, 18] indicte tht prticulrly in the domestic environment in well ventilted homes where the unttched frction of potentil lph energy cn be reltively high, on the contrry to mines, the rdon dose estimtions using two models my significntly differ. The min objective of this pper ws to mesure the rdon progeny prticle size distributions nd potentil lph energy concentrtions in the relistic domestic environment in vrious nturl rdon nd erosol conditions nd to estimte the nnul effective doses to inhbitnts of the investigted houses by mens of two pproches: epidemiologicl nd dosimetric. In the studied houses the rdon concentrtions were simultneously mesured to clculte the equilibrium fctor F. Methods nd mterils nnoying lbortory in their houses. The mesurements were lsting t lest 5 h. In some cses it ws possible to mke longer mesurements. The sme mesurements were plnned to be performed outdoors nerby the house. In ech cse, simultneously with the mesurements of the PAEC nd the rdon dughter size distributions, the rdon concentrtion ws mesured by n AlphGUARD monitor, mnufctured by Genitron (Germny) to estimte the equilibrium fctor F. The PAEC nd size distribution of the rdioctive erosols were mesured by mens of unique instrument rdon progeny prticle size spectrometer, mnufctured in the ARPNSA (Melbourne, Austrli) [14] supplied with softwre developed by Dr S. B. Solomon nd distributed by ACJ&Assocites, Inc. USA. Description of the Rdon Progeny Prticle Size Spectrometer [14] The Rdon Progeny Prticle Size Spectrometer Mk2 (RPPSS) in the configurtion for the field mesurements in the continuous mode comprises the following min components: the 8-stge smpling hed (one open fce stge, 4-stge wire screen diffusion bttery nd 3-single stge multi-hole inertil impctor system), the power supply/12-chnnel counter unit, the oil-free vcuum pump, the notebook. The schemtic modulr digrm nd smpling configurtion of the RPPSS re drwn in Fig. 1. The smpling hed consists of one open fce stge, four stge wire screen diffusion bttery system, three single stge multi-hole inertil impctor system nd smpling mnifold comprising eight inlets nd one outlet. All eight stges operte in prllel nd simultneously. Ech stge uses detector housing with PIP CAM 400 detector of the surfce of 450 mm 2 (24 mm di.) nd n luminum holder to suit 47 mm di. membrne filter or impction plte. In the first stge, with n open filter, the totl ctivity collected from the ir flown through is mesured. In the four consecutive stges the filters collect only these prticles which were not stopped by sets of wire screens preceding them in the strem of the mesured ir. In the lst three stges thin luminized mylr foils re positioned in plce of the filters which ply role of the impction surfces of the multi-hole inertil impctor. The lph prticles emitted by erosols impcted onto the impctor surfces pss through the mylr to the detector. The chrcteristics of the Mesurements indoors nd outdoors The mesurements were performed in the buildings selected ccidentlly in six regions of Polnd: in the mountins in the vicinity of Jeleni Gór nd Szczwno Zdrój, in the rurl res ner Biłystok, in the flt res ner Leżjsk nd Leszno Wielkopolskie nd in towns: Wrszw nd Włbrzych. The mesurements were mde in vrious sesons of the yer, during dytime nd in night, in houses of smokers, in well ventilted houses, in the conditions of the high (from frying nd boiling of mels) nd low levels of erosols. Selection of houses ws csul nd depended on getting permission of the inhbitnts for instlling big nd Fig. 1. Digrm of the RPPSS configurtion for field mesurements.
Studies of the rdon progeny prticle size distributions in the domestic environment 413 Tble 1. Chrcteristics of the diffusion bttery stges in the RPPSS No. of stge #1 #2 #3 #4 #5 Type of screen A A A B Number of screens 1 2 13 32 Mesh numbers 100 100 100 200 Screen dimeter (cm) 1.7 3.8 3.8 3.8 Wire dimeter (μm) 112 112 112 35 Wire thickness (μm) 215 215 215 80 Solid frction of screen (%) 31.3 31.3 31.3 29.1 Dp50 (nm) 1.2 4.3 17.3 72.3 Counting efficiency (%) 12.80 13.0 13.0 13.0 13.0 Flow rte (lpm) 4.15 4.45 4.25 4.20 4.25 RPPSS Rdon Progeny Prticie Size Spectrometer. Tble 2. Chrcteristics of the impctor stges in the RPPSS No. of stge #6 #7 #8 Number of holes 3 7 1 Dp50 (nm) 316 522 1096 Dp50 lower bound (nm) 250 500 1000 Dp50 upper bound (nm) 350 700 1400 Function slope 1.23 3.30 6.00 Function intercept 2.02 2.25 2.20 Counting efficiency (%) 21.4 21.8 21.8 Flow rte (lpm) 3.45 2.90 3.30 RPPSS Rdon Progeny Prticie Size Spectrometer. diffusion bttery nd impctor re given in Tbles 1 nd 2, respectively. The smpling hed lso comprises smpling mnifold with five inlets contining criticl orifices to set the flow t c. 4 lpm (in the first five stges) nd three inlets contining criticl orifices to set the flow t c. 3 lpm. Every time before series of the field mesurements the flow rte t ech stge is checked nd my be corrected in the progrm, if needed. The field mesurements re performed in the continuous mode of work which is controlled by PC-bsed progrm. It is designed to collect dt from ll eight stges simultneously. It integrtes the full α prticle energy spectrum for ech stge to provide gross-lph counts over set time intervl. The integrted counts re converted to the rdon progeny potentil α energy concentrtion using the effective energy rdon progeny of 7.2 MeV (1.152 10 3 nj) nd tking into ccount the flow rte, detector efficiency, bckground nd time of counting. Thus, the concentrtion of the rdon progeny is clculted by the following formul: PAEC = k N, where PAEC is the potentil α energy concentrtion in nj/m 3, N re the counts per unit of time in cpm, k is the conversion fctor in nj min/m 3 clculted s: k = 1.152/(ν eff) where ν is the flow rte in l/min, eff is the α counting efficiency of the detector. The systemtic uncertinties ssocited with the conversion of gross- -lph counts to PAEC re usully less thn 5% if the PAEC levels re bout stble, but the conversion is less ccurte when the PAEC is vrying rpidly [14]. Uncertinty of the conversion fctor k is usully less thn 5%. The low level of detection (LLD) for PAEC is c. 25 nj/m 3 with uncertinty of 30% t c. 95% confidence level. As it ws sid bove, the first stge with bre filter delivers dt on the totl PAEC, crried out by both ttched nd unttched rdon dughters. The progrm corrects for plteout of ultrfine rdon dughters in the inlet tube to the first stge. There is no correction for possible thoron dughter contribution. The progrm clcultes the dependence of the prticle penetrtion efficiency on the size of prticles ccording to the fn-filtrtion theory of Y. S. Cheng nd H. C. Yeh [4] nd Y. S. Cheng et l. [3] for the screen type diffussion bttery. For the impctor stges, the theory developed for cscde impctors by V. A. Mrple nd K. L. Rubow [10] ws modified nd pplied. The progrm clcultes the penetrtion mtrix for 43 equilogspced size intervls between 0.6 nm nd 2494 nm. Equivlent diffusion (thermodynmic) dimeters re used for the wire screen stges nd equivlent impction (erodynmic) dimeters re used for the impctor stges. The ltter re mtched to the thermodynmic dimeters using prticle density dependent function. For the vlue of the unit density, the dimeters re the sme. The derived PAEC vlues for ech stge re used s input vlues to two independent deconvolution lgorithms, one developed by S. Twomey [17] (TWOMEY) nd nother one clled Expecttion Mximiztion (EMAX) by E. F. Mher nd N. M. Lird [9]. The deconvolution nlysis results in the rdon progeny prticle size distribution. It derives for ech mode: the geometric men dimeter (ctivity medin erodynmic dimeter-amad in nm), geometric stndrd devition nd the percentge contribution to the potentil lph energy concentrtion. In order to clculte the size-weighted DCF for the obtined prticle size distribution in the smpled ir the progrm pplies the ICRP 66 Respirtory Trct Model implemented in the computer progrm RADEP (rdon dose evlution progrm) by A. Birchll nd A. C. Jmes [1]. The dependence of the DCF for n dult mle with brething rtes of 1.2 m 3 /h (hrd working) nd 0.78 m 3 /h (generl popultion) on the prticle dimeter pplied in this progrm is shown in Fig. 2. It ws ssumed tht the representtive ctivity concentrtion rtios for 218 Po: 214 Pb: 214 Bi is 0.8:0.02:0.0 nd 0.8:0.4:0.2, for prticle sizes < 20 nm nd 20 nm, respectively. Figure 2 shows tht the dose per unit exposure (DCF) is bout fctor of 25 times higher for the prticle size of c. 1 nm (the unttched frction) thn for the prticle size in the rnge 100 300 nm (the ttched frction). The RADEP-derived DCF vlues re normlized by fctor of 0.3 [8] to provide consistency with the results
414 K. Mmont-Cieśl, O. Stwrz Fig. 2. The dependence of the DCF on the prticle dimeter dp for monodispersed prticles. Assumptions: rtio of ctivity concentrtion: 218 Po: 214 Pb: 214 Bi of 0.8:0.02:0.0 for dp < 20 nm nd of 0.8:0.4:0.2 for dp 20 nm. derived from the epidemiologicl risk estimte with the use of the ICRP 65 conversion convention. This fctor ws chosen to mtch the RADEP-derived DCF vlues to the ICRP 65 conversion convention for the urnium mine erosol conditions. It will be discussed in section Summry of this pper. The progrm pplies the collection efficiency curves for the eight stges, in the dimeter rnge from 0.6 to 2496 nm which re shown in Fig. 3. Before nd fter ech series of mesurements the flow rte nd counting efficiency t ech of eight stges were checked. The counting efficiency stbility ws verified by mens of control Pu-239 source plced insted of the filter in the diffusion bttery (DB) stges nd the mylr foil in the impctors. In Tbles 1 nd 2 chrcteristics of ll stges nd typicl vlues of the flow rte re presented. The mesurements performed in Centrl Lbortory for Rdiologicl Protection (CLOR, Wrsw, Fig. 3. The collection efficiency curves for ll 8 stges in the RPPSS. Polnd) rdon chmber in two kinds of erosol conditions: low erosols (< 200 CN/cm 3 ) nd high erosols (c. 20 000 CN/cm 3 ), (CN condenstion nuclei), reveled good consistency between results obtined by mens of two lgorithms: TWOMEY nd EMAX. Comprison of the DCF nd the prticle size distributions clculted by two lgorithms for the low nd high erosol conditions in the CLOR rdon chmber re given in Tble 3. According to the estimtion mde by S. B. Solomon [13, 14] the uncertinty of the DCFs for the polidispersion size distribution reches ± 10% for workers nd ± 20% for the generl popultion. The nnul effective doses from rdon progeny During the mesurements, the progrm every hour delivers PAEC vlues nd two vlues of the DCF for ech of two lgorithms: DCF Env for the generl popultion nd DCF Occ for hrd working men. To ssess the n- Tble 3. Comprison of the DCFs nd the prticle size distributions delivered by two lgorithms EMAX nd TWOMEY for low (< 200 CN/cm 3 ) nd high (c. 20 000 CN/cm 3 ) erosol conditions in the CLOR rdon chmber < 200 CN/cm 3 Generl popultion Workers EMAX DCF 2086 4364 TWOMEY DCF 2294 4781 Mode #1 Mode #2 Mode #3 EMAX GMD b (nm) 0.7 418 1378 Contribution (%) 87 3 10 TWOMEY GMD (nm) 0.6 343 1375 Contribution (%) 84 5 11 20 000 CN/cm 3 Generl popultion Workers EMAX DCF 579 983 TWOMEY DCF 629 1069 Mode #1 Mode #2 Mode #3 EMAX GMD b (nm) 1.1 157 730 Contribution (%) 0.07 91 9 TWOMEY GMD (nm) 1.3 169 761 Contribution (%) 0.04 92 8 CN condenstion nuclei. b GMD geometric medin dimeter.
Studies of the rdon progeny prticle size distributions in the domestic environment 415 Tble 4. The prticle size distributions indoors Nme of plce Mode #1 Mode #2 Mode #3 GMD (nm) GSD b U c (%) GMD (nm) GSD U (%) GMD (nm) GSD U (%) BukGj4K 0.7; 8 1.4 46 166 1.9 48 1345 1.4 6.3 BukGj4K b 0.8; 6 1.6 16 139 1.9 77 878 1.5 7.0 BukGj4P 0.8 1.7 12 158 1.9 85 1236 1.4 2.8 BukGj4P b 0.8 1.6 22 208 2.0 78 BukGj3K 0.7 1.4 18 154 1.7 73 685 1.4 9.6 BukGj3K b 0.8 1.7 29 199 2.1 71 BukGj3 S 0.7 1.4 22 207 1.9 78 Kurosiówk 0.8 1.6 14 149 1.6 81 813 1.5 5.2 Kurosiówk b 0.7 1.4 20 154 1.7 73 743 1.5 7.4 SzlrskP 0.8 1.5 27 156 1.7 68 884 1.5 5.0 Borowice 0.7 1.4 17 128 2.0 77 685 1.5 6.5 Grodzisko 0.8 1.3 48 187 1.3 56 1592 1.3 2.5 Leszno Gierym. 0.9 1.4 21 167 1.4 75 835 1.4 5.0 Leszno Olsz. 1.0 1.4 32 165 1.4 62 Lipno 0.8 1.6 27 150 1.5 70 1086 1.4 2.7 Osieczn 0.8 1.3 30 169 1.4 70 939 1.5 6.6 Poniec Dom 179 1.4 92 631 1.3 8.0 Poniec wr. 0.9 1.4 16 172 1.3 78 660 1.4 6.0 Rokosowo 0.8 1.3 27 173 1.4 69 851 1.4 3.8 Michłów 1 1.0 1.7 5 130 1.6 92 724 1.1 3.0 Michłów 2 0.7 1.3 11 144 1.4 78 774 1.2 11.0 Studzinki 1 0.8 1.3 24 170 1.3 70 847 1.3 6.0 Studzinki 2 1.0 1.6 15 145 1.5 81 752 1.2 5.0 Studzinki 2b 1.1 1.8 1 121 1.7 97 747 1.2 2.1 Studzinki 3 0.8 1.4 10 139 1.4 82 773 1.1 8.1 Studzinki 3b 0.8 1.4 0.2 136 1.4 91 780 1.1 9.0 Giedlrow 0.8 1.4 17 124 1.9 81 778 1.5 2.0 Grodzisko 0.7 1.4 17 129 1.8 80 817 1.6 3.5 Grodzisko b 0.8 1.4 9 130 1.7 89 700 1.4 3.0 Gielershof 0.8 1.3 16 184 1.8 84 Leżjsk Rynek 0.8 1.5 20 133 2.3 81 Włbrzych 1 5.9 1.8 2 135 1.6 94 888 1.3 4.8 Włbrzych 2 0.8 1.5 6 147 1.5 89 789 1.3 5.3 Włbrzych 2b 0.7 1.6 13 142 1.5 83 849 1.4 5.0 Włbrzych 3 0.7 1.4 11 147 1.4 86 923 1.4 3.0 Szczwno 0.7 1.3 12 152 1.5 85 1007 1.4 3.1 Jnowice 1 0.7 1.2 7 140 1.4 90 1009 1.2 3.2 Jnowice 1b 0.6 1.2 17 151 1.4 79 909 1.2 4.3 Jnowice 2 0.7 1.2 13 143 1.4 82 1042 1.3 6.0 Jnowice 2b 0.6 1.2 19 130 1.3 75 1030 1.3 5.6 Syt2 0.2 1.7 19 134 1.5 78 1011 1.3 2.9 Wilnów 2.0 2.1 25 155 1.7 68 789 1.5 7.2 Wilnów b 1.1 1.7 4 172 1.4 85 753 1.3 11.0 Służew 1.1 1.8 25 157 1.6 68 789 1.4 7.2 Służew b 1.9 2.5 17 145 1.8 72 660 1.3 3.0 Wesoł 0.1 2.0 20 134 1.7 74 794 1.3 6.0 Wesoł b 1.0 1.7 12 145 1.5 82 1110 1.4 6.4 Bemowo 0.7 1.4 53 123 2.8 40 919 1.7 7.0 Bemowo b 1.2 1.6 16 138 1.6 79 895 1.2 5.6 Ochot 0.6 1.2 30 153 2.1 70 1361 1.4 1.6 Ochot b 0.6 1.2 19 141 1.8 80 655 1.3 2.5 Śródmieście 1.0 1.7 10 151 1.5 80 721 1.2 9.7 Śródmieście b 1.4 1.8 1 152 1.5 88 713 1.2 11.0 Żerń 1.0 1.6 1 156 1.5 91 709 1.4 7.8 Żerń b 0.9 1.7 6 160 1.4 80 755 1.2 14.0 Arithmetic men 0.9 1.5 18 152 1.6 78 874 1.4 6.0 GMD geometric men dimeter. b GSD geometric stndrd devition. c U percentge contribution.
416 K. Mmont-Cieśl, O. Stwrz Fig. 4. Histogrms of the rdon concentrtions C Rn, PAEC, unttched frctions f p, equilibrium fctors F, dosimetric doses: HE Env nd HE Occ nd rtios of the dosimetric to epidemiologicl dose for the generl public nd hrd working men, indoors.
Studies of the rdon progeny prticle size distributions in the domestic environment 417 nul effective doses in the tested rooms the EMAX DCF vlues were used. Although the min objective of this pper is indoor doses to the generl popultion, there re lso clculted doses to the hrd working dult men in the sme rdon nd erosol conditions to compre the differences between dosimetric nd epidemiologicl dose estimtes in the two cohorts. The doses estimted for two models were clculted ccording to the following formule: for the dosimetric model: HE Occ = PAEC DCF Occ t nd HE Env = PAEC DCF Env t for the epidemiologicl model: D Occ = PAEC 1425 t nd D Env = PAEC 1100 t where: HE Occ, HE Env, D Occ nd D Env re in msv/y, PAEC in nj/m 3, DCF Occ nd DCF Env in msv/(j h/m 3 ) nd t = 8760 h/y. Results nd discussion Altogether in six regions of Polnd there were gthered results in 54 houses nd only four results in the outdoor tmosphere becuse in the most of the outdoor mesurements the sttistics ws too low to deliver relible results. In Tble 4 there re given the following chrcteristics of the prticle size distributions indoors: the geometric men dimeter (GMD), the geometric stndrd devition (GSD) nd the percentge contribution (U) of ech mode to the distribution for ech mesurement site. In the mjority of cses three modes pper: mode #1, corresponding to the unttched frction f p, of GMD in the rnge: 0.2 8 nm, mode #2, corresponding to the dominting mbient frction in the distribution, of GMD in the rnge from 98 to 208 nm nd mode #3, corresponding to the biggest prticles, of GMD in the rnge from 631 to 1532 nm. The mode #2 with rithmetic mens of the GMD, GSD nd U equl to 152 nm, 1.6 nd 78% nd mode #3 with rithmetic mens of the GMD, GSD nd U equl to 874 nm, 1.4 nd 6% mke the ttched frction. Only in three sites ppered two modes #1 nd #2 nd in one site mode #2 nd mode #3. Vlues of the GSD of the dimeters for ll three modes rnge from 1 to 2 in the mjority of cses. In only 5 cses they slightly exceed 2. In Fig. 4 there re frequency distributions of the obtined results of the rdon concentrtion C Rn, potentil lph energy concentrtion PAEC, equilibrium coefficient F, unttched frction f p, dosimetric doses: HE Env nd HE Occ nd rtios of the effective nnul doses ssessed by mens of two models: dosimetric nd epidemiologicl for the generl popultion nd hrd working men. In the tested houses the rdon concentrtions rnges from 19 to 1668 Bq/m 3 with n rithmethic men of 300 Bq/m 3 (geometric men of 140 Bq/m 3, medin of 103 Bq/m 3 ). In five houses rdon concentrtion exceeds 1000 Bq/m 3, in eight houses it flls in the limits of 400 to 1000 Bq/m 3 nd in forty three houses it is below 400 Bq/m 3 the upper limit recommended by the Europen Union in older dwellings. The vlues of the PAEC rnge from 64 to 3805 nj/m 3. The frction of the unttched frction f p chnges from below the detection limit of 0.2 to 53% with n rithmethic men of 17% (geometric men of 12% nd medin of 17%). The highest vlues, bove 30%, were detected in four rurl houses well ventilted during bsence of nybody in the room. The equilibrium fctor F rnges from 8 to 64% with n rithmetic men of 32% (geometric men of 27% nd medin of 29%). A. Reineking nd J. Porstendorfer found close men vlue of 30% for F nd bit less of c. 10% for f p in their studies [12]. Although the observed rnge of the fctor F is rther wide but the rithmetic men of 32% is in pretty good greement with the vlue of 40% recommended in the routine estimtions of the PAEC on the bsis of the rdon concentrtion mesurements [2, 19]. The highest vlues of the fctor F, bove 60%, were mesured in seven cses in the conditions of boiling, frying or smoking cigrettes. Thus, normlly the high vlues of the fctor F re not permnent, they correspond rther to short-lived ctivities. The differences between the vlues of the doses estimted by the two models depend on the frction of the unttched frction f p. According to the dosimetric models, the dose conversion fctors increse nerly linerly with the unttched frction f p. Therefore, the dependence of the rtios of the dosimetric to epidemiologicl doses on the vlue of f p, shown in Fig. 5, is lso well described s liner. The rtios fll in the limits between 0.6 nd 1.7 with n rithmetic, geometric men nd medin equl to 1.0 for the generl popultion nd of 0.8 to 2.6 with n rithmetic, geometric men nd medin equl to 1.4 for the hrd working dult mle. In Fig. 5 it cn be seen tht the epidemiologicl doses re underestimted compred to the dosimetric doses up to 1.7 times for the generl popultion nd up to 2.6 times in cse of the hrd working men. S. B. Solomon received similr results for guides in Firy Cve in Austrli [15]. He estimted tht the rdon dose to which the guides re exposed during work, if clculted s n epidemiologicl dose, is underestimted c. two times compred to dosimetric one. It is worthy of underling tht the vlue of the brething rte dmitted in the clcultion is of significnt influence on the resulting dose. There re suggestions tht for the hrd working men the brething rte vlue of 1.7 m 3 /h should be dmitted rther thn 1.2 m 3 /h [19]. In Fig. 6 the courses in time of C Rn, PAEC, F, f p, HE Occ, HE Env doses, HE Occ/D Occ nd HE Env/D Env 3 2 HE/D 1 0 y = 0,03x + 0,82 R 2 = 0,91 HE Env/D1.1 HE Occ/D1.4 y = 0,02x + 0,64 R 2 = 0,85 0 10 20 30 40 50 60 fp [%] Fig. 5. Rtios of the dosimetric to epidemiologicl dose estimtes vs. the unttched frction f p.
418 K. Mmont-Cieśl, O. Stwrz Fig. 6. Courses in time of C Rn, PAEC, F, f p, HE Occ, HE Env nd rtios of HE/D in house in Wrsw. At c. 19:00 cigrette ws smoked. rtios during longer mesurement in Wrsw house re plotted. It cn be seen tht t c. 19:00 inhbitnts smoked cigrettes wht cused n increse in the PAEC from 100 nj/m 3 to 400 nj/m 3, in the equilibrium fctor F from 10 to 58% nd in the nnul dose from c. 200 msv to c. 450 msv (for popultion) nd drop in the f p from 48 to 15% nd in the rtio of the two dose estimtes from 1.8 to 1 (for popultion). Outdoors It ws plnned to mke mesurements lso nerby ll the investigted houses. But only in four sites, ll in the Sudety region, the counting sttistics ws high enough to deliver relible results. In Tble 5 there re modes in the prticle size distributions outdoors. In three cses there re just two modes with men of the GMD of 0.8 nm for the unttched frction nd 175 nm for the ttched frction. In the fourth cse the ttched frction hs two modes: 138 nm (79%) nd 814 nm (9%). The men contribution of the unttched frction (mode #1) is 19%. In Tble 6 there re results of f p, PAEC, C Rn, both kinds of doses HE Env nd D Env, HE Occ nd D Occ nd the rtios of the dosimetric to the epidemiologicl dose for the hrd working nd generl popultion. Vlues of the f p nd F rnge from 12 to 31% nd from 6 to 33%, respectively. The men rtio of the two doses for the generl popultion nd hrd working men is equl to 1.0 nd 1.4, respectively, the sme s for the indoor results. Tble 5. The prticle size distributions outdoors Nme of plce Mode #1 Mode #2 Mode #3 GMD (nm) GSD b U c (%) GMD (nm) GSD U (%) GMD (nm) GSD U (%) Przesiek 0.8 0.6 19 195 1.9 81 Borowice 0.7 1.3 14 138 2.9 86 Kurosiówk 0.8 1.4 31 229 2.5 69 Jnowice Wlk. 0.7 1.2 12 138 1.4 79 814 1.2 9.0 Arithmetic men 0.8 1.1 19 175 2.2 79 GMD geometric men dimeter. b GSD geometric stndrd devition. c U percentge contribution.
Studies of the rdon progeny prticle size distributions in the domestic environment 419 Tble 6. Results of the mesurements nd clcultions in four outdoors sites Nme of plce f p (%) F (%) PAEC (nj/m 3 ) C Rn (Bq/m 3 ) HE Env (msv/y) D Env (msv/y) HE Env/ D Env HE Occ (msv/y) D Occ (msv/y) HE Occ/ D Occ Przesiek 19 33 144 79 1.31 1.39 0.94 2.48 1.80 1.38 Borowice 14 31 201 116 2.10 1.94 1.08 3.80 2.51 1.51 Kurosiówk 31 17 77 83 0.87 0.74 1.17 1.70 0.96 1.77 Jnowice Wlk. 12 6 28 82 0.21 0.27 0.80 0.39 0.35 1.11 Arithmetic men 19 22 113 90 1.1 1.1 1.0 2.1 1.4 1.4 Conclusions The experimentl mteril collected during the mesurements in 56 dwellings in vrious conditions of the rdon nd erosol concentrtions leds to the following conclusions: The unttched frction f p nd equilibrium fctor F sty in brod rnges from nerly 0 to 53% with men of 18% nd 8 to 64% with men of 32%, respectively nd re influenced by the behviour of the inhbitnts, such s, e.g. cooking or smoking cigrettes (Fig. 6). When cigrette ws lit in the Wrsw F [%] 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 80 fp [%] Fig. 7. The reltions: F vs. f p for the indoor nd outdoor results. Fig. 8. The equilibrium fctor F vs. the unttched frction f p, in the CLOR rdon chmber. house the PAEC, the equilibrium fctor F nd the nnul dose incresed four, six nd two nd hlf times, respectively. The unttched frction f p nd the rtio of the two dose estimtes decresed c. 3 nd c. 2 times, respectively. The highest vlues of the fctor F were found during cooking or smoking. In nturl domestic conditions negtive correltion between the equilibrium fctor F nd the unttched frction f p corresponding to mny vrious houses is not observed, s it is illustrted in Fig. 7, on the contrry to the rtificil conditions in the rdon chmber (Fig. 8). The difference cn result from the different conditions of deposition nd ventiltion in vrious nturl domestic environment, while they re stble in the chmber. Since ccording to the dosimetric models the dose conversion fctors increse nerly linerly with the unttched frction f p, the dependence of the rtios of the dosimetric to epidemiologicl doses on the unttched frction is lso well described by liner eqution, s it is shown in Fig. 5. An rithmetic men of the rtios of the dosimetric to epidemiologicl dose estimtes for the generl popultion is 1.0 nd for the working men is 1.4. Summry In generl, there is quite good greement between vlues of the effective doses estimted by mens of so rdiclly different pproches, but we should remember tht ll vlues of the dosimetric dose estimtes in the bove clcultions were obtined with the use of fctor of 0.3 to mtch the RADEP-derived DCF vlues to the ICRP 65 conversion convention [5]. Thus, question rises if the two different pproches cn be reconciled. J. Stther [16] exmined the min fctors underlying the discrepncy between the two pproches nd he indicted tht the tissue nd rdition weighting fctors, dmitted s w T = 0.12 nd w R = 20, my substntilly influence this discrepncy. However, the 2007 ICRP new recommendtions (Publiction 103) [7] mintined the sme vlues for w T nd w R. On the bsis of the more recent miner epidemiologicl studies on the risks t low levels of the rdon exposure Publiction 103 provides updted vlues of detriment per unit effective dose for low level exposure: 4.2 10 5 /msv for workers nd 5.7 10 5 / msv for the generl public [11]. Using these vlues together with the revised risk coefficient of 5 10 4 / WLM the new vlues of the rdon progeny conversion WLM (working level month) is trditionl unit of exposure to rdon dughters. 1 WLM = 12.97 J. s. m 3.
420 K. Mmont-Cieśl, O. Stwrz convention, re recommended. They re 9 msv/wlm (c. 2500 msv/(j h m 3 )) insted of 4 msv/wlm for members of the public nd 12 msv/wlm (c. 3333 msv/ (J h m 3 )) insted of 5 msv/wlm (1425 msv/(j h m 3 )) for workers. The new vlues of the conversion conventions re c. 2.3 times higher thn the previous ones wht mkes the results of the two pproches remrkbly closer. Acknowledgment. This work ws supported by the Ministry of Science nd Informtiztion within the frme of the project no. 5 T07E 008 25. References 1. Birchll A, Jmes AC (1994) Uncertinty nlysis of the effective dose per unit exposure from rdon progeny nd implictions for ICRP risk-weighting fctor. Rdit Prot Dosim 53;1/4:133 140 2. Cvllo A (2000) The rdon equilibrium fctor nd comprtive dosimetry in homes nd mines. Rdit Prot Dosim 92;4:295 298 3. Cheng YS, Keting JA, Knpilly GM (1980) Theory nd clibrtion of screen type diffusion bttery. J Aerosol Sci 11:549 556 4. Cheng YS, Yeh HC (1980) Theory of screen type diffusion bttery. J Aerosol Sci 11:313 319 5. Interntionl Commission on Rdiologicl Protection (1993) Protection ginst Rdon-222 t home nd t work. ICRP Publiction 65, Ann ICRP 23(2) 6. Interntionl Commission on Rdiologicl Protection (1994) Humn respirtory trct model for rdiologicl protection. ICRP Publiction 66, Ann ICRP 24(1 3) 7. Interntionl Commission on Rdiologicl Protection (2007) The 2007 recommendtions of the Interntionl Commission on Rdiologicl Protection. ICRP Publiction 103, Ann ICRP 37(2 4) 8. Jmes AC, Birchll A (1995) New ICRP lung dosimetry nd its risk implictions for lph emitters. Rdit Prot Dosim 60;4:321 326 9. Mher EF, Lird NM (1985) Algorithm reconstruction of prticle size distributions from diffusion bttery dt. J Aerosol Sci 16:557 570 10. Mrple VA, Rubow KL (1986) Theory nd design guidelines, cscde impctors: Smpling of dt. Chpter 4. In: Lodge JP, Chn TL (eds) Cscde impctor: smplying nd dt nlysis. Americn Industril Hygiene Assocition, Akron, OH 11. Mrsh JW, Hrrison JD, Lurier D, Blnchrdon E, Pquet F, Tirmrch M (2010) Dose conversion fctors for rdon: recent developments. Helth Phys 99;4:511 516 12. Reineking A, Porstendorfer J (1990) Unttched frction of short-lived Rn decy products in indoor nd outdoor environments: n improved single-screen method nd results. Helth Phys 58;6:715 725 13. Solomon SB (1997) A rdon progeny smpler for the determintion of effective dose. Rdit Prot Dosim 72:31 42 14. Solomon SB (1999) Mnul for Rdon Progeny Prticle Size Spectrometer (RPPSS) Mk2. ARPANSA, Yllmbie, Austrli 15. Solomon SB (2001) Field tests of rdon progeny smpler for the determintion of effective dose. Sci Totl Environ 272:303 313 16. Stther JW (2004) Dosimetric nd epidemiologicl pproches to ssessing rdon doses cn the differences be reconciled. Rdit Prot Dosim 112;4:487 492 17. Twomey S (1975) Comprison of constrined liner inversion nd itertive lgorithm ppllied to the indirect estimtion of the prticle size distribution. J Comput Phys 18:188 200 18. Wąsiołek PT, Hopke PK, Jmes AC (1992) Assessment of exposure to rdon decy products in relistic living conditions. J Exposure Anl Environ Epidemiol 2;3:309 322 19. Zock C, Porstendorfer J, Reineking A (1996) The influence of biologicl nd erosol prmeters of inhled short-lived rdon decy products on humn lung dose. Rdit Prot Dosim 63;3:197 206