Chapter 30 Updating Radon Daughter Bronchial Dosimetry Naomi H. Harley and Beverly S. Cohen Institute of Environmental Medicine, New York University Medical Center, New York, NY 10016 The lung cancer risk from radon daughter exposure is known only for occupationally exposed males. In order to determine the risk in environmental situations it is necessary to determine whether the bronchial alpha dose, which confers the risk, is similar to that in mines. Particle size is a major factor which determines the alpha dose conversion factor for radon daughters (mGy/WLM). Data on indoor environments are emerging and indicate that a variety of specific conditions exist. For example, a dose factor four times that for a nominal occupational or environmental exposure exists if kerosene heater particles dominate the indoor aerosol and four times smaller if a hygroscopic particle dominates. Many states in the U.S. are currently involved in large scale surveys to measure radon levels in homes in an attempt to assess the environmental risk from radon and radon daughter exposure. Radon daughters deliver the largest radiation exposure to the population and it is estimated that 0.01% of the U.S. population (23,000 persons) are exposed from natural sources to greater than those levels allowed occupationally (4 WLM/yr) (NCRP, 1984). In order to estimate the risk from environmental exposure it is necessary to utilize the underground miner epidemiology which relies exclusively upon data from occupationally exposed males. It is possible to infer cross population risk if the detailed dose delivered to target cells in bronchial epithelium is calculated for the various population groups since it is the dose which confers the risk. 0097-6156/87/0331-0419$06.00/0 © 1987 American Chemical Society
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RADON AND ITS DECAY PRODUCTS
S e v e r a l models have been p u b l i s h e d c o n c e r n i n g t h e b r o n c h i a l d o s i m e t r y f o r radon daughters ( H a r l e y , 1984; ICRP, 1981? James, 1984) and these a r e i n g e n e r a l agreement p r o v i d e d t h a t t h e r e f e r e n c e atmosphere i s chosen t o be s i m i l a r . I t i s i m p o r t a n t t o update t h e b r o n c h i a l d o s i m e t r y f o r radon daughters as new i n f o r m a t i o n becomes a v a i l a b l e . I t i s t h e purpose o f t h i s s t u d y t o show t h a t t h e r e i s a p o t e n t i a l f o r e i t h e r s i g n i f i c a n t l y i n c r e a s e d b r o n c h i a l dose i n t h e home p e r u n i t exposure i f t h e ambient p a r t i c l e s i z e i s a r t i f i c i a l l y reduced due, f o r example, t o open-flame b u r n i n g o r use o f kerosene h e a t e r s , o r a d e c r e a s e d dose i f h y g r o s c o p i c p a r t i c l e s dominate t h e i n d o o r a e r o s o l . Indoor C h a r a c t e r i s t i c s Recent measurements have i n d i c a t e d t h a t t h e i n d o o r a e r o s o l i s g e n e r a t e d p r i m a r i l y i n d o o r s (Tu e t a l . , 1985) u n l e s s t h e d w e l l i n g i s , f o r example, a p u b l i c b u i l d i n g w i t h h i g h v e n t i l a t i o n r a t e s (Walker e t a l . , 1980). Spengler (Spengler e t . a l . , 1984) has shown t h a t a s i n g l e smoker i n a home can double t h e normal p a r t i c l e l o a d i n g from about 20 t o 40 jug/m . Measurements made i n an energy e f f i c i e n t t e s t home (0.1 a i r changes/hr) showed t h a t one c i g a r e t t e dominated t h e i n d o o r a e r o s o l c h a r a c t e r i s t i c s f o r many hours (Offerman e t a l . , 1985). A l t h o u g h many f a c t o r s need t o be c o n s i d e r e d i n c a l c u l a t i n g the a l p h a dose t o t a r g e t c e l l s i n b r o n c h i a l e p i t h e l i u m , many o f the f a c t o r s do not produce a l a r g e change i n t h e dose c o n v e r s i o n f a c t o r (mGy/WLM) ( H a r l e y , 1984). The p a r t i c l e s i z e d i s t r i b u t i o n , however, i s a s e n s i t i v e f a c t o r i n t h e c a l c u l a t i o n o f b r o n c h i a l dose and s m a l l e r o r l a r g e r p a r t i c l e s i z e s than u s u a l l y assumed f o r t h e i n d o o r a e r o s o l can produce a s u b s t a n t i a l i n c r e a s e o r decrease i n t h e b r o n c h i a l dose. The p a r t i c l e s i z e chosen i n p a s t radon daughter dose e s t i m a t e s f o r o c c u p a t i o n a l and e n v i r o n m e n t a l exposure was from t h e work o f George e t a l . (1975) and George and B r e s l i n (1980) who r e p o r t e d mines t o have p a r t i c l e s w i t h a c t i v i t y median d i a m e t e r o f 0.18 urn, and homes, 0.12 urn. Extensive measurements o f t h e i n d o o r e n v i r o n m e n t a l p a r t i c l e s i z e d i s t r i b u t i o n a r e not a v a i l a b l e , b u t e x i s t i n g d a t a i n d i c a t e a l a r g e p o t e n t i a l f o r d i f f e r e n c e s from t h i s v a l u e . Tu e t a l . (1985) measured s e v e r a l types o f i n d o o r e n v i r o n m e n t a l a e r o s o l s and found t h a t w i t h open flame b u r n i n g o r w i t h t h e use o f kerosene h e a t e r s , t h e r e s u l t i n g h y d r o p h o b i c p a r t i c l e s dominated t h e i n d o o r a e r o s o l . T h e i r measurements a l s o show t h a t c i g a r e t t e smoke can dominate t h e i n d o o r a e r o s o l . I t i s assumed h e r e , f o r purposes o f c a l c u l a t i n g a range o f dose f a c t o r s t h a t a h y g r o s c o p i c p a r t i c l e can a l s o be p r e s e n t i n t h e environment. Tu (1986) has c a l c u l a t e d t h e a c t i v i t y median diameter f o r radon daughter attachment i n two houses from h i s measurements f o r these d i f f e r i n g situations and these are shown i n Table I . 3
30.
HARLEY AND
Updating Radon Daughter Bronchial Dosimetry
COHEN
All
T a b l e I . C a l c u l a t e d a c t i v i t y median diameter f o r a t t a c h e d radon daughters from measured a e r o s o l c h a r a c t e r i s t i c s (Tu, 1986). Site
A c t i v i t y median diameter (jam)
geometric s t a n d a r d
House A normal room a i r c i g a r e t t e smoked
0.075 0.123
1.8 1.79
House Β normal room a i r kerosene h e a t e r on
0.086 0.030
1.8 1.92
deviation
Tu and Knutson (1984) a l s o measured the p a r t i c l e d e p o s i t i o n of h y d r o p h o b i c and h y g r o s c o p i c p a r t i c l e s i n the human r e s p i r a t o r y t r a c t . They showed t h a t the h y g r o s c o p i c p a r t i c l e s grow by a f a c t o r of 3.5 to 4.5 at the s a t u r a t e d h u m i d i t y p r e s e n t i n the l u n g . For the purpose of c a l c u l a t i n g b r o n c h i a l d e p o s i t i o n f o r a h y g r o s c o p i c a e r o s o l we assume an i n c r e a s e i n s i z e by a f a c t o r of 4 upon e n t r y i n t o the b r o n c h i a l t r e e . T r a c h e o b r o n c h i a l Dose The t r a c h e o b r o n c h i a l dose has been c a l c u l a t e d p r e v i o u s l y u s i n g average r e p o r t e d v a l u e s f o r the v a r i o u s f a c t o r s needed ( H a r l e y , 1984). The f o l l o w i n g l i s t of f a c t o r s i n v o l v e d i n the dose c a l c u l a t i o n i n d i c a t e s where d i f f e r e n c e s i n the modeling o c c u r s f o r t h i s update. Physical
characteristics
Unattached f r a c t i o n of daughters The same. Mines Po/ R n = 4%; i n d o o r s 7%. Po/ Pb=10. (NCRP, 1984a). D i f f u s i o n c o e f f i c i e n t a f t e r Knutson et a l . (1983) of 0.0025 cm /sec. 2 1 8
2 2 2
2 1 8
2 1 4
2
Radon daughter d i s e q u i l i b r i u m Different. Rn/ Po/ Pb/ B i , nominal mine 1/.61/.29/.21 (George et a l . , 1975); nominal home 1/.9/.6/.4 (Fisenne and H a r l e y , 1974). High p a r t i c l e home 1/.9/.7/.7., assumed s i m i l a r to o u t d o o r s (Fisenne and H a r l e y , 1974) 2 2 2
2 1 8
2 1 4
2 1 4
P a r t i c l e d e p o s i t i o n models D i f f e r e n t . Ingham (1975) d i f f u s i o n d e p o s i t i o n but c o r r e c t e d by t u r b u l e n t d i f f u s i o n f a c t o r s i n a i r w a y s 0 t o 6 as measured Cohen (1986). Particle size distribution D i f f e r e n t . Nominal c a l c u l a t i o n f o r mine and home but adding c a l c u l a t i o n s which i n c l u d e kerosene h e a t e r p a r t i c l e s and h y g r o s c o p i c p a r t i c l e s . (Tu et a l . , 1985)
by
RADON AND ITS DECAY PRODUCTS
422 P h y s i c a l dose c a l c u l a t i o n Same as H a r l e y (1984). Biological
characteristics
Breathing pattern/nasal deposition Same as H a r l e y (1984). B r o n c h i a l morphometry Same as i n H a r l e y (1984) from Yeh and Schum
(1980).
Mucociliary clearance rates Same as H a r l e y (1984). Location of target c e l l s Same as H a r l e y (1984). Mucus t h i c k n e s s Same as H a r l e y
(1984).
The s p e c i f i c v a l u e s o f t h e p h y s i c a l and b i o l o g i c a l c h a r a c t e r i s t i c s such as b r e a t h i n g p a t t e r n s f o r o c c u p a t i o n a l exposure and a c t i v e and r e s t i n g p a t t e r n s f o r e n v i r o n m e n t a l exposure a r e g i v e n i n t h e f o o t n o t e s t o t h e T a b l e s . A few remarks s h o u l d be made c o n c e r n i n g t h e parameters used which a f f e c t t h e dose c a l c u l a t i o n s i g n i f i c a n t l y . In t h e p r e s e n t study t h e b r o n c h i a l morphometry o f Yeh and Schum (1980) i s u t i l i z e d i n s t e a d o f t h e Weibel model. T h i s i s a more a c c u r a t e d e s c r i p t i o n o f t h e b r o n c h i a l a i r w a y l e n g t h s , d i a m e t e r s and b r a n c h i n g p a t t e r n . I t does not assume dichotomous b r a n c h i n g and t h e r e f o r e does n o t s u f f e r from t h e problem o f t h e a r t i f i c i a l l y h i g h s u r f a c e a r e a l e a d i n g t o low a l p h a dose i n t h e more d i s t a l a i r w a y s common t o o t h e r models o f t h e human a i r w a y s . I t i s w e l l known t h a t enhanced d e p o s i t i o n i n t h e f i r s t few a i r w a y s o c c u r s due t o t h e t u r b u l e n c e produced. Turbulent d i f f u s i o n i s accounted f o r by u s i n g f a c t o r s ( r a t i o o f observed deposition t o c a l c u l a t e d d i f f u s i o n deposition) t o c o r r e c t the d i f f u s i o n d e p o s i t i o n . These had f o r m e r l y been measured by M a r t i n and J a c o b i (1972) i n a dichotomous p l a s t i c model o f t h e upper a i r w a y s . The d a t a used here a r e from measurements performed by Cohen (1986) u s i n g h o l l o w c a s t s o f t h e upper b r o n c h i a l t r e e which i n c l u d e d a l a r y n x . T h i s c a s t was t e s t e d u s i n g c y c l i c f l o w w i t h d e p o s i t i o n measured f o r 0.03, 0.15 and 0.20 urn diameter p a r t i c l e s . Her t u r b u l e n t d i f f u s i o n f a c t o r s a r e used i n t h e c a l c u l a t i o n here (14 f o r g e n e r a t i o n 0, and 2 f o r g e n e r a t i o n s 1 t o 6). There a r e o n l y s c a n t d a t a on n a s a l d e p o s i t i o n . The a v a i l a b l e s t u d i e s r e p o r t e d u t i l i z e d micron s i z e d p a r t i c l e s and the dominant mode o f d e p o s i t i o n i s i m p a c t i o n . T h i s i s not t h e case f o r t h e p a r t i c l e s c o n s i d e r e d here and d i f f u s i o n and t u r b u l e n t d i f f u s i o n a r e t h e mechanisms o f i n t e r e s t . George and
30.
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Updating Radon Daughter Bronchial Dosimetry
B r e s l i n (1969) measured n a s a l d e p o s i t i o n f o r both the a t t a c h e d and u n a t t a c h e d f r a c t i o n of radon daughters i n a l a b o r a t o r y atmosphere and found i t t o be about 1% f o r the a t t a c h e d and 60% f o r the u n a t t a c h e d f r a c t i o n . The s i z e c h a r a c t e r i s t i c s of the u n a t t a c h e d f r a c t i o n i s assumed t o be t h a t found by Knutson e t a l . (1983) f o r o l d e r a i r of 0.005 μπι (D=0.0025 c m / s e c ) . No d a t a are a v a i l a b l e f o r n a s a l d e p o s i t i o n of the s m a l l s i z e d kerosene h e a t e r p a r t i c l e s , 0.030 um, and the v a l u e f o r the a t t a c h e d radon daughters of 1.3% i s used. 2
R e s u l t s and C o n c l u s i o n s The c a l c u l a t i o n s are shown f o r the a d u l t male b r e a t h i n g under normal e n v i r o n m e n t a l c o n d i t i o n s . The a l p h a dose combines the daytime and n i g h t t i m e b r e a t h i n g p a t t e r n s . T a b l e I I shows the nominal a l p h a dose f a c t o r s f o r o c c u p a t i o n a l m i n i n g exposure. T a b l e I I I shows the a l p h a dose f a c t o r s f o r the nominal e n v i r o n m e n t a l s i t u a t i o n . T a b l e IV shows the b r o n c h i a l dose f a c t o r s f o r the s m a l l e s t s i z e d p a r t i c l e s , t h a t dominated by the kerosene h e a t e r or 0.03 μπι. p a r t i c l e s . The radon daughter e q u i l i b r i u m was s h i f t e d t o a somewhat h i g h e r v a l u e i n t h i s c a l c u l a t i o n because t h i s s o u r c e of p a r t i c l e s g e n e r a l l y e l e v a t e s the p a r t i c l e c o n c e n t r a t i o n markedly w i t h consequent i n c r e a s e i n the daughter e q u i l i b r i u m . T a b l e V shows the a l p h a dose f o r a 0.12 μιη p a r t i c l e , the same as the nominal i n d o o r a e r o s o l p a r t i c l e , but f o r a p a r t i c l e which i s assumed t o be h y g r o s c o p i c and grows by a f a c t o r of 4, t o 0.5 μπι, once i n the bronchial tree. The c a l c u l a t i o n of e f f e c t i v e dose e q u i v a l e n t i s sometimes used even when r e p o r t i n g v a l u e s f o r n a t u r a l r a d i o a c t i v i t y . The concept of e f f e c t i v e dose e q u i v a l e n t was developed f o r o c c u p a t i o n a l exposures so t h a t d i f f e r e n t t y p e s of exposure t o v a r i o u s organs c o u l d be u n i f i e d i n terms of cancer r i s k . It is h i g h l y u n l i k e l y t h a t the g e n e r a l p o p u l a t i o n would r e q u i r e summation of r i s k s from s e v e r a l s o u r c e s of r a d i a t i o n exposure. The normal or average r i s k from whole body gamma-ray exposure i n the environment i s o n l y about 10% of t h a t from average radon daughter exposure and much l e s s i n e l e v a t e d i n d o o r environments. C o n s i d e r i n g t h a t the radon daughter l u n g cancer r i s k can be d e r i v e d d i r e c t l y from exposure i n most c a s e s , e f f e c t i v e dose e q u i v a l e n t i s an unnecessary s t e p . The r e s u l t s i n T a b l e s I I t o V i n d i c a t e t h a t a range of a l p h a dose f a c t o r s f o r radon d a u g h t e r s of about a f a c t o r of t e n e x i s t s and t h a t they a r e s i t e s p e c i f i c depending p r i m a r i l y on the i n d o o r a e r o s o l . The p o t e n t i a l f o r d e l i v e r i n g an a l p h a dose f o u r times g r e a t e r o r s m a l l e r than t h a t i n a nominal atmosphere e x i s t s i f t h e r e i s e i t h e r a s m a l l s i z e d or h y g r o s c o p i c a e r o s o l . The c a l c u l a t i o n s have been performed here f o r males, but i t has been shown t h a t t h i s model i s e a s i l y adapted t o c a l c u l a t i n g the a l p h a dose t o women, c h i l d r e n and i n f a n t s ( H a r l e y , 1984).
423
424
RADON AND ITS DECAY PRODUCTS
TABLE I I . A l p h a Dose i n mGy/WLM f o r O c c u p a t i o n a l M i n i n g Atmosphere. B r e a t h i n g P a t t e r n and S p e c i f i c C o n d i t i o n s , See Footnote
LOBE
GEN
RIGHT UPPER
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
5.4 3.5 4.5 4.5 4.0 3.8 3.9 2.8 3.6 5.5 4.7 5.2 6.2 6.8 0.0 0.0 0.0
RIGHT MIDDLE 5.4 3.5 3.1 3.8 4.0 3.8 4.3 3.5 4.8 7.1 6.0 7.3 7.5 7.9 10.0 0.0 0.0
RIGHT LOWER
LEFT UPPER
LEFT LOWER
5.4 3.5 3.1 3.2 3.1 3.0 2.9 2.7 2.7 2.8 1.7 2.1 2.3 2.5 2.7 3.1 3.5
5.4 3.3 3.9 3.9 3.7 3.5 3.4 2.8 2.9 4.2 3.1 3.4 3.5 3.9 0.0 0.0 0.0
5.4 3.3 3.2 3.2 3.1 3.0 2.8 2.3 2.3 2.4 1.6 1.8 2.1 2.6 3.2 0.0 0.0
Unattached daughters Po-218/Rn, 4.0%; Pb-214/Rn, 0.4%. Daughter R a t i o Rn/Po-218/Pb-214/Po-214 1/.61/.29/.21. B r e a t h i n g P a t t e r n 18 1pm, 15 B r e a t h s / m i n . B r e a t h i n g c y c l e - i n s p i r a t i o n , pause, e x p i r a t i o n , pause (3/8, 1/8, 3/8, 1/8) D i f f u s i o n C o e f f i c i e n t f o r Unattached 0.0025 cm /sec. P a r t i c l e diameter 0.17 nm (AMD) f o r A t t a c h e d Daughters N a s a l D e p o s i t i o n 1.3% f o r A t t a c h e d and 60% f o r Unattached Daughters A l p h a dose t o c e l l s a t 22 μπι depth below e p i t h e l i a l s u r f a c e Twenty p e r c e n t a l v e o l a r d e p o s i t i o n p r i o r t o e x p i r a t i o n 2
30. HARLEY AND COHEN
Updating Radon Daughter Bronchial Dosimetry
425
TABLE I I I . A l p h a Dose i n mGy/WLM f o r Males. Environmental A e r o s o l . B r e a t h i n g P a t t e r n and S p e c i f i c C o n d i t i o n s , See F o o t n o t e .
LOBE
GEN
RIGHT UPPER
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
6.1 4.1 5.2 5.1 4.6 4.4 4.5 3.3 4.2 6.4 5.5 6.1 7.3 8.1 0.0 0.0 0.0
RIGHT MIDDLE 6.1 4.1 3.6 4.5 4.6 4.4 5.0 4.1 5.7 8.4 7.1 8.7 8.9 9.5 12.0 0.0 0.0
RIGHT LOWER
LEFT UPPER
LEFT LOWER
6.1 4.1 3.6 3.7 3.6 3.4 3.4 3.2 3.2 3.3 2.0 2.4 2.7 3.0 3.3 3.8 4.2
6.1 3.8 4.5 4.5 4.3 4.0 3.9 3.2 3.4 4.9 3.6 4.0 4.1 4.6 0.0 0.0 0.0
6.1 3.8 3.7 3.7 3.6 3.5 3.2 2.7 2.7 2.9 1.9 2.1 2.5 3.1 3.9 0.0 0.0
Unattached Daughters. Ρο-218/Rn, 7.0%, Pb-214/Rn, 0.7% Daughter R a t i o Rn/Po-218/Pb-214/Po-214 1/.9/.6/.4. B r e a t h i n g P a t t e r n 18 1pm a c t i v e , 15 B r e a t h s / m i n . B r e a t h i n g P a t t e r n 9 1pm r e s t i n g , 12 B r e a t h s / m i n . B r e a t h i n g P a t t e r n , 16 Hours A c t i v e , 8 Hours R e s t i n g D i f f u s i o n C o e f f i c i e n t f o r Unattached 0.0025 cm /sec. P a r t i c l e diameter 0.12 pm (AMD) f o r A t t a c h e d Daughters N a s a l D e p o s i t i o n 1.3% f o r A t t a c h e d and 60% f o r Unattached Daughters A l p h a dose t o c e l l s a t 22 jam depth below e p i t h e l i a l s u r f a c e 2
426
RADON AND ITS DECAY PRODUCTS
TABLE IV. A l p h a Dose i n mGy/WLM f o r Males. Kerosene Heater A e r o s o l . B r e a t h i n g P a t t e r n and S p e c i f i c C o n d i t i o n s , See F o o t n o t e .
LOBE
GEN
RIGHT UPPER
RIGHT MIDDLE
RIGHT LOWER
LEFT UPPER
LEFT LOWER
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
26.7 17.9 22.7 22.2 20.0 19.3 20.0 14.4 18.7 28.7 25.0 28.2 33.7 37.0 0.0 0.0 0.0
26.7 17.9 15.9 19.3 20.1 19.4 21.9 17.9 24.8 37.3 32.3 39.8 41.0 43.6 54.7 0.0 0.0
26.7 17.9 15.9 16.1 15.5 14.9 14.6 13.7 14.0 14.5 9.1 11.0 12.5 13.7 15.0 17.2 19.1
26.7 17.0 19.7 19.7 18.9 17.8 17.2 14.2 15.1 22.2 16.5 18.4 19.1 21.1 0.0 0.0 0.0
26.7 17.0 16.5 16.3 16.0 15.3 14.2 12.1 12.2 12.9 8.7 9.7 11.7 14.2 17.6 0.0 0.0
Unattached Daughters,Po-218/Rn 7.0%, Pb-214/Rn, 0.7% Daughter R a t i o Rn/Po-218/Pb-214/Po-214 1/.9/.7/.7. B r e a t h i n g P a t t e r n 18 1pm a c t i v e , 15 B r e a t h s / m i n . B r e a t h i n g P a t t e r n 9 1pm r e s t i n g , 12 B r e a t h s / m i n . B r e a t h i n g P a t t e r n , 16 Hours A c t i v e , 8 Hours R e s t i n g D i f f u s i o n C o e f f i c i e n t f o r Unattached 0.0025 cm /sec. P a r t i c l e diameter 0.03 μπι (AMD) f o r A t t a c h e d Daughters N a s a l D e p o s i t i o n 1.3% f o r A t t a c h e d and 60% f o r Unattached Daughters A l p h a dose t o c e l l s a t 22 \xm depth below e p i t h e l i a l s u r f a c e 2
HARLEY AND COHEN
TABLE V. Aerosol.
Updating Radon Daughter Bronchial Dosimetry
421
A l p h a Dose i n mGy/WLM f o r Males. Hygroscopic B r e a t h i n g P a t t e r n and S p e c i f i c C o n d i t i o n s , See F o o t n o t e .
LOBE
GEN
RIGHT UPPER
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
2.7 1.7 2.2 2.2 1.9 1.8 1.9 1.3 1.7 2.5 2.1 2.3 2.7 3.0 0.0 0.0 0.0
RIGHT MIDDLE 2.7 1.7 1.5 1.9 1.9 1.8 2.1 1.7 2.2 3.2 2.7 3.2 3.2 3.4 4.2 0.0 0.0
RIGHT LOWER
LEFT UPPER
LEFT LOWER
2.7 1.7 1.5 1.5 1.5 1.4 1.4 1.3 1.3 1.3 0.8 0.9 1.0 1.1 1.1 1.3 1.4
2.7 1.6 1.9 1.9 1.8 1.6 1.6 1.3 1.3 1.9 1.3 1.5 1.5 1.6 0.0 0.0 0.0
2.7 1.6 1.5 1.5 1.5 1.4 1.3 1.1 1.1 1.1 0.7 0.8 0.9 1.1 1.3 0.0 0.0
Unattached Daughters. RaA/Rn, 7.0%, RaB/Rn, 0.7% Radon Daughter R a t i o Rn/RaA/RaB/RaC' 1/.9/.6/.4. B r e a t h i n g P a t t e r n 18 1pm a c t i v e , 15 B r e a t h s / m i n . B r e a t h i n g P a t t e r n 9 1pm r e s t i n g , 12 B r e a t h s / m i n . B r e a t h i n g P a t t e r n , 16 Hours A c t i v e , 8 Hours R e s t i n g D i f f u s i o n C o e f f i c i e n t f o r Unattached 0.0025 c m / s e c . P a r t i c l e diameter 0.12 μπι (AMD) f o r A t t a c h e d Daughters Assume h y g r o s c o p i c w i t h 4x growth i n a i r w a y s t o 0.5 μπι N a s a l D e p o s i t i o n 1.3% f o r A t t a c h e d and 60% f o r Unattached Daughters A l p h a dose t o c e l l s a t 22 μπι depth below e p i t h e l i a l s u r f a c e 2
428
RADON AND ITS DECAY PRODUCTS
Acknowledgments The authors would like to thank Dr. Keng Tu of the USDOE Environmental Measurements Laboratory for allowing us to use his unpublished calculations. This work was performed with support from USDOE Contract DE AC02 80 EV 10374 and in part by Center Grants ES00260 and CA13343 from NIEHS and the National Cancer Institute and Special Emphasis Research Career Award Grant No. OH 00022 from NIOSH. All support is gratefully acknowledged. Literature Cited Cohen, B.S., Deposition of Ultrafine Particles in the Human Tracheobronchial Tree: A Determinant of the Dose from Radon Daughters, Proc. Am. Chem. Soc. Annual Meeting 1986, New York. Fisenne, I.M. and N.H. Harley, Lung Dose Estimates from Natural Radioactivity Measured in Urban Air, USAEC Report HASL-TM-74-7 New York, NY (1974). George, A.C. and A.J. Breslin, Deposition of Radon Daughters in Humans Exposed to Uranium Mine Atmospheres, HealthPhys.17:115124 (1969). George, A.C., L. Hinchliffe, and R. Sladowski, Size Distribution of Radon Daughter Particles in Uranium Mine Atmospheres, Am. Ind. Hyg. J., 36:484-490 (1975). George, A.C. and A.J. Breslin, The Distribution of Ambient Radon and Radon Daughters in Residential Buildings in the New Jersey-New York Area, in Natural Radiation Environment III; (Gesell, T.and W. Lowder, Eds.); National Technical Information Service, Springfield, VA. (1980). Harley, N.H., Comparing Radon Daughter Dose:Environmental versus Underground Exposure, Rad. Protection Dosimetry 7:371-375 (1984). ICRP, "Limits for Inhalation of Radon Daughters by Workers," International Commission on Radiation Protection Report 32, Pergamon Press, New York, 1981. Ingham, D.B., Diffusion of Aerosols from a Stream Flowing Through a Cylindrical Tube, J. Aero. Sci., 6: 125-132 (1975). James, A. C., Dosimetric Assessment of Risk from Exposure to Radioactivity in Mine Air Proc. Occupational Radiation Safety in Mining, (H. Stocker, ed) pp415-426 Canadian Nuclear Assn.,Toronto, Canada (1984). Knutson, E.O., A.C. George, R.H. Knuth and B.R. Koh, Radon Daughter Plateout II. Prediction Model, Health Phys. 45:445-452 (1983).
30.
HARLEY AND COHEN
Updating Radon Daughter Bronchial Dosimetry
Martin, D. and W. Jacobi, Diffusion Deposition of Small-sized Particles in the Bronchial Tree,HealthPhys.23: 23-29 (1972).
NCRP, "Exposures from the Uranium Series with Emphasis on Radon and its Daughters," National Council on Radiation Protection and Measurements Report No. 77. Bethesda, MD. (1984) NCRP, "Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States," National Council on Radiation Protection and Measurements Report No. 78 Bethesda, MD (1984a). Offermann, F.J., R.G. Sextro, W.J. Fisk, D.T. Grimsrud, W.W. Nazaroff, A.V. Nero, K.L. Revzan, K.L. and J. Yater, Control of Respirable Particles in Indoor Air with Portable Air Cleaners, Atmo. Env. 19: 1761-1775 (1985). Spengler, J.D. and K. Sexton, Indoor Air Pollution: A Public Health Perspective, Science, 221: 9-17 (1983). Tu, K.W. and E.O. Knutson, Total Deposition of Ultrafine Hydrophobic and Hygroscopic Aerosols in the Human Respiratory System, Aerosol Sci. and Technology, 453-465 (1984). Tu, K.W., E.O. Knutson and H. Franklin, Aerosol Measurements in Residential Buildings in New Jersey, Abstract. Am. Assoc. for Aerosol Res. Annual Meeting. Albuquerque, NM. (1985). Tu, K.W. Private communication. 1986. Walker, M.V. and C.J. Weschler, Water-Soluble Components of SizeFractionated Aerosols Collected after Hours in a Modern Office Building, Env. Sci and Technology 14:594-597 (1980). Yeh, H.C. and M. Schum, Models of Human Lung Airways and their Application to Inhaled Particle Deposition, Bull. Math Biol. 42: 461-480 (1980). RECEIVED
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