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- Löndahl, Jakob, et al.
(författare)
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A set-up for field studies of respiratory tract deposition of fine and ultrafine particles in humans
- 2006
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 37:9, s. 1152-1163
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Tidskriftsartikel (refereegranskat)abstract
- Respiratory tract deposition data of ultrafine aerosol particles, hygroscopic particles and ambient particles in general are scarce. Measurements are associated with several difficulties. The objective of this work was to design a method for fast determination of highly size-resolved fine and ultrafine particle deposition, to be used on larger groups of human subjects in exposure studies and in typical ambient and indoor environments. The particle size distributions in dried samples of the inhaled and exhaled air are characterised with an electrical mobility spectrometer. A particle counter desmearing procedure reduces the spectrometer scan time. The precision and sensitivity of the method was tested for hygroscopic sodium chloride (NaCl) and hydrophobic Di-Ethyl-Hexyl-Sebacate (DEHS) aerosols in repeated identical experiments and experiments with different breathing frequencies on a single subject. The accuracy of the method was estimated by comparing results from three subjects with previous data obtained with monodisperse particles and with the well-established International Commission on Radiological Protection model (1994). Potential errors due to size shifts between the inhaled and exhaled samples and coagulation were simulated. The system has low losses in the studied particle size range (10-475 nm), typically 10% or less of the fraction deposited in the respiratory tract. Coagulation is noticeable at 10(5) cm(-3) but can be corrected for up to 5 x 10(5) cm(-3). The precision in the determined deposited fraction is 0.02-0.08. The method is sensitive enough to quantify differences between breathing patterns and differences between hygroscopic and hydrophobic aerosols. Our results for NaCl and DEHS are in agreement with the ICRP 66 model [International Commission on Radiological Protection. (1994). Human respiratory tract model for radiological protection (ICRP Publication 66). Oxford, UK: Elsevier Science], and also suggest that the relative humidity in the respiratory tract is close to 99.5%. A respiratory tract deposition measurement can be done in 15-30 min. Recommendations are given for field applications of the method. (C) 2005 Elsevier Ltd. All rights reserved.
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| 3. |
- Löndahl, Jakob, et al.
(författare)
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Experimentally Determined Human Respiratory Tract Deposition of Airborne Particles at a Busy Street
- 2009
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 43:13, s. 4659-4664
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Tidskriftsartikel (refereegranskat)abstract
- Traffic is one of the major sources of harmful airborne particles worldwide. To relate exposure to adverse health effects it is important to determine the deposition probability of the inhaled particles in the human respiratory tract. The size-dependent deposition of 12-580 nm particles was measured with a novel setup in 9 healthy subjects breathing by mouth on the windward side of a busy street in Copenhagen, Denmark. The aerosol was characterized both at the curbside and, to obtain the background concentration, at rooftop level. Particle hygroscopicity, a key parameter affecting respiratory tract deposition, was also measured at the same time of exposure. The total deposition fraction of the curbside particles in the range 12-580 nm was 0.60 by number, 0.29 by surface area, and 0.23 by mass. The deposition fractions of the "traffic exhaust" contribution, calculated as the hydrophobic fraction of the curbside particles, was 0.68, 0.35, and 0.28 by number, surface area, and mass, respectively. The deposited amount of traffic exhaust particles was 16 times higher by number and 3 times higher by surface area compared to the deposition of residential biofuel combustion particles investigated previously (equal inhaled mass concentrations). This was because the traffic exhaust particles had both a higher deposition probability and a higher number and surface area concentration per unit mass. To validate the results, the respiratory tract deposition was estimated by using the well-established ICRP. model. Predictions were in agreement with experimental results when the effects of particle hygroscopicity were considered in the model.
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