Condensational Growth May Contribute to the Enhanced Deposition of Cigarette Smoke Particles in the Upper Respiratory Tract

Figures & data

FIG. 1 Surface model of the upper respiratory tract including the oral airway, larynx, and upper tracheobronchial region as viewed from the (a) front and (b) back. The surface model extends through respiratory generation G6 along some paths.

TABLE 1 Initial temperature and relative humidity conditions at the mouth inlet ranging from sub-saturated to saturated conditions

Case	Inhaled temperature	Inhaled relative humidity (RH)	Representative description
1	23°C (296.15 K)	30%	Cool ambient SS smoke
2	27°C (300.15 K)	60%	Warm ambient SS smoke
3	40°C (313.15 K)	100%	Warm saturated MS smoke
4	47°C (320.15 K)	100%	Hot saturated MS smoke

TABLE 2 Name, cross-sectional area, and flow ratio of the outlet bronchi

		Name*	Area (mm^2)	Flow ratio ^‡ (%)
	0	Trachea	283.6
Left Upper Lobe flow ratio: 15.98%	1	L_up_apx	77.0	4.01
	2	L_up_ant	76.2	3.97
	3	L_up_post	50.2	2.61
	4	L_up_inf	76.2	5.39
Left Lower Lobe flow ratio: 23.90%	5	L_low_apx	52.9	3.19
	6	L_low_ant_med	43.7	3.11
	7	L_low_ant_lat	47.1	3.35
	8	L_low_post_med	59.9	6.42
	9	L_low_post_post	23.0	2.47
	10	L_low_post_lat	50.0	5.36
Right Upper Lobe flow ratio: 18.16%	11	R_up_apx	71.2	6.20
	12	R_up_post	57.3	4.99
	13	R_up_ant	80.1	6.97
Right Middle Lobe flow ratio: 11.67%	14	R_mid_lat_ant	45.1	4.47
	15	R_mid_lat_post	28.6	2.83
	16	R_mid_med_ant	18.2	1.80
	17	R_mid_med_post	26.0	2.57
Right Lower Lobe flow ratio: 30.29%	18	R_low_ant	69.4	6.87
	19	R_low_lat_ant	34.7	3.44
	20	R_low_lat_post	51.5	5.10
	21	R_low_med_med	52.4	5.19
	22	R_low_med_mid	61.5	6.08
	23	R_low_med_lat	36.5	3.61
Total:				100

TABLE 3 Initial properties of cigarette smoke particles (CSPs) for mainstream (MS) and sidestream (SS) conditions

Smoke conditions	Molecular wt. of soluble component Ms [kg/kmol]	Initial liquid mass fraction of water [%]	Initial mass ratio of soluble to non-soluble components [%]	Droplet density ρ d [g/cm ^3]
MS	340 (Ishizu et al. 1980)	8–25 (Ishizu et al. 1980; Norman 1977)	60 (Li and Hopke 1993)	1.00
SS	450 (Ishizu et al. 1980)	6–25 (Ishizu et al. 1980; Norman 1977)	54 (Li and Hopke 1993)	1.00

FIG. 2 Comparison of submicrometer particle deposition with existing experimental results for the (a) mouth-throat (MT) geometry, and (b) tracheobronchial (TB) region.

FIG. 3 Equilibrium diameter change vs. initial particle size (d _o ) due to hygroscopic growth for mainstream (MS) and sidestream (SS) smoke particles at relative humidity (RH) values of (a) 99.5% and (b) 99.75%.

FIG. 4 Equilibrium diameter change for MS and SS particles as a function of RH.

FIG. 5 Time history of CSP size change as a function of RH for (a) condensational growth and (b) evaporation.

FIG. 6 Steady state temperature profiles for inhalation Case 2 (T_inlet = 27°C, RH_inlet = 60%): (a) in the midplane, and at selected cross-sectional slices of the (b) mouth-throat, (c) right lung, and (d) left lung.

FIG. 7 Steady state RH profiles for inhalation Case 2 (T_inlet = 27°C, RH_inlet = 60%): (a) in the midplane, and at selected cross-sectional slices of the (b) mouth-throat, (c) right lung, and (d) left lung.

FIG. 8 Steady state temperature profiles for inhalation Case 3 (T_inlet = 40°C, RH_inlet = 100%): (a) in the midplane, and at selected cross-sectional slices of the (b) mouth-throat, (c) right lung, and (d) left lung.

FIG. 9 Steady state RH profiles for inhalation Case 3 (T_inlet = 40°C, RH_inlet = 100%): (a) in the midplane, and at selected cross-sectional slices of the (b) mouth-throat, (c) right lung, and (d) left lung.

FIG. 10 Droplet trajectories colored according to transient size for inhalation conditions (a) Case 1, (b) Case 2, (c) Case 3, and (d) Case 4.

FIG. 11 Particle size distribution presented as mass fraction per micrometer for initially 200 nm particles under (a) sub-saturated and (b) saturated conditions; as well as 400 nm particles under (c) sub-saturated and (d) saturated conditions.

TABLE 4 Particle size statistics with evaporation and condensational growth in the upper respiratory airway sampled at Slice A

	200 nm		400 nm
Initial diameter	CMAD (μ m)	MMAD (μ m)	CMAD (μ m)	MMAD (μ m)
Case 1	0.176	0.189	0.352	0.370
Case 2	0.182	0.197	0.368	0.387
Case 3	3.18	3.63	3.23	3.98
Case 4	6.24	7.21	6.39	7.45
CMAD: count median aerodynamic diameter.
MMAD: mass median aerodynamic diameter.

FIG. 12 Deposition under Case 3 inhalation conditions for initially 200 nm particles (a) without condensational growth and (b) with condensational growth. The associated deposition enhancement factor (DEF) is shown (c) without condensational growth and (d) with condensational growth.

FIG. 13 Cumulative particle deposition fraction (DF) as a percentage along the x-axis of the geometry for (a) Case 3 and (b) Case 4 inhalation conditions.

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