CIGARETTE SMOKE

POLONIUM-210 DOSIMETRY

[References also in Pediatrics Vol. 92 No. 3 September, 1993]

____________________________________________________________

Po-210 inhaled per cigarette package of 20

Each cig.: 0.1 - 0.5 pCi Po-210 with average estimate = 0.3 pCi. (1)
Each 20 pack: 0.3 pCi x 20 = 6 pCi Po-210 contained in 20 cigarette package of which:
~18% remains in butt,
~10% remains in filter,
~50% remains in ash
~22% moves into smoke fraction = 0.22 x 6 pCi = 1.32 pCi Po-210 in smoke / pkg)
~15% smoke produced is inhaled = 1.32 pCi x 0.15 = 0.198pCi Po210 inhaled / pkg)

Polonium-210 deposition into epithelium

From ICRP (2): 25% of smoke Po-210 is deposited in seg. bronchi & beyond = 0.25 x 0.198pCi = 0.05 pCi
From ICRP (2): 60% of inhaled is retained long term via deposition into seg.- term. bronchial epithelium
= 0.050 pCi x 0.6 = 0.03 pCi Po-210 is retained in smoker of 1 package of cigs.
Adult lung (3) Tracheal + Large bronchial epithelial mass = 0.527 grams
Segmental bronchial epithelial mass = 1.062 grams
Smaller and terminal bronchial epithelial mass = 1.966 grams
Thus: 0.03 pCi Po-210 is deposited into (1.062 grams + 1.966 grams) of epithelial tissue
= 3.028 grams over an effective time of (T Po / 0.693) = 200 days.

Calculation of radiation dose to epithelial from 1 pkg of cigarettes:

(0.03x10^-12Ci)(3.7x10^10disint/sec)(5.305MeV/disint)(1.60207x10^-6 ergs/MeV) x ...
... (60s/min)(60m/h)(24h/d)(200d/effective particle lifetime)=0.1630 ergs into 3.028 gms = ...
... 0.0538 ergs/gram epith. tissue.
Gamma particles: rem = 100 ergs/gram
Alpha particles: rem = 5 ergs/gram (Given Alpha RBE = 20x gamma)
Therefore: (0.0538 ergs/gram)(1 rem/(5 ergs/gram)=0.01076 rem=10.8 mrem dose/cigarette package
Moderate to heavy smoker smokes 2 packs per day x 365 days per year.
Dose = (10.8 mrem/pkg per day) (2 pkgs per day) x (365 days/yr) = 7884 mrem/yr
= 7.9 rem/yr deposited into bronchial epithelium / year of smoking 2 packs per day, 365 days per year.

Summary:

A moderate to heavy cigarette smoker of 1 packs per day receives ~8 rem/year Po210 irradiation to segmental and terminal bronchial epithelial tissues. That is about equivalent to 300 chest x-ray exposures per year!

________________________________

Conversions 1 Ci = 3.7 x 1010 disintegrations/second
1 rad = 100 ergs/gram
1 rem = 0.05 rad for alpha particles of RBE=20
1 MeV = 1.60207 x 10-6 ergs
Po-210 alpha particle energy = 5.305 MeV
t for Polonium = 138.4 days
Effective residency time = t / 0.693

_______________________

References:

1. Health Physics 49:296-301; 1985 Mussalo-Rauhamaa H, et al (re: 0.1 to 0.5 pCi) Po-210 per cigarette.
2. ICRP Task Group on Lung Dynamics; 1966
3. See lung epithelial calculations
4. BEIR V 1/1990 -T.Bronchial epith. cell mass calc's. (Reconstructed from Gofman and from the ICRP):

Trachea and mainstem bronchi Volume of air in NP, trachea, tracheobronchi extending to terminal bronchi = 133 cc of which NP volume = 50cc. Therefore vol. of tracheobronchial tree excluding alveoli = 133-50 cc = 83cc (ICRP). Tracheal vol. = 33 cc. Mainstem bronchial vol.= 11 cc. Segmental + terminal Brochi & bronchioles = 39cc (ICRP). Tracheal volume + mainstem bronchial volume (33 cc + 11 cc) = 44 cc. Average diameter of the trachea and large bronchi = 1cm. (radius = 0.5cm). Consider trachea and bronchi as cylindrical tubes. Therefore Vol = pr2 h = 44 cc = (3.14159)(0.5)(0.5)(h) solving for h: h = 56 cms. Area of cylindrical surface (epithelial lining) = 2prh = (2)(3.14159)(0.5)(56) = 175.8cm2 Average epithelial cell thickness = 30 micrometers = 0.003 cms. Volume of epithelial cells = area x thickness = (175.8 cm2) (0.003 cm) = 0.527 cc. Therefore mass of tracheal and mainstem bronchial epithelial cells = 0.527 grams at approx. 1gm/cc density. Mass of tracheal and mainstem bronchial epithelium (at ~1gm/cc density) = 0.527 grams. Segmental bronchi from the above the volume of the resp. tree beyond trach+mainstem bronchi = 39 cc, of which ~ volume is of segmental bronchi and of smaller bronchial branches. Using 20 cc for volume of segmental bronchi of diameter of 0.23cm (from Gray's Anatomy) this yields an average for segmental bronchial radii of 0.115 cms. Therefore Vol = pr2 h = 20cc = (3.14159)(0.115)(0.115)(h) solving for h: h = 490 cms. Area of cylindrical surface (epithelial lining) = 2prh = (2)(3.14159)(0.115)(490) = 354 sq.cm. Average epithelial cell thickness = 30 micrometers = 0.003 cms. Volume of epithelial cells = area x thickness = (354 cm2) (0.003 cm) = 1.062 cc. Mass of segmental bronchi epithelium (at ~1gm/cc density) = 1.062 grams. Terminal bronchi Using the remaining volume (83cc - 44 cc - 20 cc = 19 cc) for area of terminal bronchioles of average radius of 0.058 cm (again from Gray's Anatomy). Therefore Vol = pr2 h = 19 cc = (3.14159)(0.058)(0.058)(h) solving for h: h = 1799 cm. Area of cylindrical surface (epithelial lining) = 2prh = (2)(3.14159)(0.058)(1799) = 655.3 sq.cm. Average epithelial cell thickness = 30 micrometers = 0.003 cms.Volume of epithelial cells = area x thickness = (655.3 cm2) (0.003 cm) = 1.966 cc. Mass of terminal bronchiolar epithelium (at ~1gm/cc density) = 1.966 grams. Summary: Trachea and mainstem bronchi = 0.527 grams Segmental bronchi = 1.062 grams Smaller bronchi through term. bronchioles = 1.966 grams

______________________________________________