Pagels, Joakim; Löndahl, Jakob; Zhou, Jingchuan; Bohgard, Mats; Swietlicki, Erik

Transcription

1 A Set-up for Feld Studes of Respratory Deposton n Humans Pagels, Joakm; Löndahl, Jakob; Zhou, Jngchuan; Bohgard, Mats; Swetlck, Erk 2005 Lnk to publcaton Ctaton for publshed verson (APA): Pagels, J., Löndahl, J., Zhou, J., Bohgard, M., & Swetlck, E. (2005). A Set-up for Feld Studes of Respratory Deposton n Humans. Paper presented at ICEE, Internatonal Conference on Envronmental, Ystad, Sweden. General rghts Copyrght and moral rghts for the publcatons made accessble n the publc portal are retaned by the authors and/or other copyrght owners and t s a condton of accessng publcatons that users recognse and abde by the legal requrements assocated wth these rghts. Users may download and prnt one copy of any publcaton from the publc portal for the purpose of prvate study or research. You may not further dstrbute the materal or use t for any proft-makng actvty or commercal gan You may freely dstrbute the URL dentfyng the publcaton n the publc portal Take down polcy If you beleve that ths document breaches copyrght please contact us provdng detals, and we wll remove access to the work mmedately and nvestgate your clam. L UNDUNI VERS I TY PO Box L und

2 A SET-UP FOR FIELD STUDIES OF RESPIRATORY DEPOSITION IN HUMANS Joakm Pagels1, Jakob Löndahl2, Jngchuan Zhou2, Mats Bohgard1 and Erk Swetlck2 1 Dv. of Ergonomcs and Aerosol Technology, Lund Unversty, P.O. Box 118, SE-22100, Lund, Sweden 2 Dv. of Nuclear Physcs, Lund Unversty, P.O. Box 118, SE-22100, Lund, Sweden Introducton It has been estmated that arborne partcles n ambent ar (e.g. PM10 and PM2.5) leads to a loss of 6.4 mllon years of healthy lfe annually n the world (WHO 2003). The correspondng estmate for Europe s 750,000 years (WHO 2002; Ezzat et al. 2002) and for Sweden 2,500 years (Forsberg et al. 2005). It has been suggested that fne and ultrafne partcles, especally from combuston sources, have a stronger assocaton wth adverse health effects than larger partcles (Donaldson et al. 2001). The bologcal mechansms by whch partcles affect health at moderate levels n the ndustralsed world are not fully understood. Susceptble sub-groups such as people wth pre-exstng respratory or cardovascular dseases, elderly and chldren have been dentfed. In 1881, Tyndall made the frst observaton of aerosol partcle deposton n the respratory system. The probablty of an nhaled partcle to be deposted n the human arways depends on ts sze, shape and chemcal composton as well as on the breathng pattern and arway geometry of the nhalng person. The term respratory deposton refers to the mean probablty for an nhaled partcle to be deposted n the respratory system. Most knowledge of respratory deposton comes from measurements of partcle concentraton n nhaled and exhaled ar usng monodsperse hydrophobc partcles n healthy young testpersons. There are surprsngly few expermental data avalable for ambent partcles and ultrafne partcles n general. In addton there are only few expermental data for ultrafne partcle deposton n susceptble sub-groups (Chalupa et al. 2004). To fll ths gap there s a need for expermental methods wth whch large groups can be studed n varous envronments e.g. at the low concentratons often encountered for ambent partcles. An mportant parameter rarely taken nto account s the hygroscopc growth nto soluton droplets that occurs n the respratory tract for soluble speces The am of ths work was to develop and characterse a fast respratory deposton method sutable for feld measurements n humans. The method should have well-documented accuracy and allow fast measurements (less than 15 mn). Respratory Deposton Method The system can be dvded nto three man parts: aerosol generaton, breathng system and measurement system. The two latter parts are shown n fgure 1. Aerosol Generaton Two dfferent sources of aerosol were used, hygroscopc sodum chlorde and hydrpophobc d-ethylhexyl-sebacate (DEHS). Polydsperse aerosol was generated wth a nebulser (Model 3076, TSI Inc., US), sodum chlorde from a dstlled water soluton wth 1% salt and DEHS from an ethanol solutıon wıth 0.1% DEHS, whch resulted n a dred aerosol wth a number geometrc mean dameter (GMD) of nm. In experments nvolvng human test persons the wet aerosol from the nebulser passed a sngle nozzle mpactor wth a cut-off dameter of 0.7 m. Ths reduced the mass concentraton by a factor of The ethanol was subsequently adsorbed n two actve charcoal denuders. The aerosols were dluted wth partcle free ar n a 1 m3 box n order to decrease the RH below and acheve the desred number concentratons (50, ,000 cm-3). Typcally a partcle concentraton of 90,000 cm-3 was chosen. The arrangement of the system s shown n Fgure 1. It bascally conssts of a mouthpece, two tanks made of stanless steel connected by a T-shaped brass pece wth two one-way valves, an automatc two-way valve, a drer and a partcle spectrometer. When a human test-person nhales, ar s drawn actvely from the larger tank for nhaled ar. Inhaled and exhaled ar s separated by two one-way valves (Lp membrane, Laerdal medcal, Norway), of the duck-bll type, whch opens wth mnmal flow obstructon. The valves are made of slcon rubber, but were covered wth a 50 nm thck layer of gold appled wth vacuum deposton (Auto 306, Edwards, UK) to decrease losses by electrostatc deposton. The exhaled aerosol enters a smaller tank that s heated to C to prevent condensaton. Both the nhalaton tank and the exhalaton tank are thus open to the surroundng atmosphere and operate at pressures near ambent. The breathng contnues untl a suffcent number of partcles are counted to 300

3 calculate the deposton, normally between 10 and 20 mnutes dependng on the aerosol concentraton. A pressure transducer (PasCal 100, Hoffrchter, Germany) connected to a pneumotachograph (Type 1, Dr. Fenyves und Gut, Germany) s used to regster the exhaled flow-rate and breathng frequency. Temperature and RH are measured n the aerosol samplng lnes just after ext from the two tanks usng capactve sensors (Hygroclp S, Rotronc, Swtzerland). Measurement System In both systems the aerosol concentraton s measured n the reservors for nhaled and exhaled ar. The samplng locaton s chosen wth a computer controlled two-way valve (Solenod Valve, type 330, Bürkert, Germany). The aerosol s dred wth a 48 Nafon sngle tube drer (MD-070, Perma Pure, NJ, USA), whch reduces the RH to below 25%. Measurement of the partcle sze dstrbuton was made wth a scannng moblty partcle szer consstng of a dfferental moblty analyser (DMA, Model 3071, TSI Inc., US) and a condensaton partcle counter (CPC, Model 3010, TSI Inc., US). The DMA s operated n a closed loop set-up wth a dffuson drer (Model 3062, TSI Inc., US) n the sheath flow to reduce the RH n the DMA to below 5%. Temperature and RH s measured after the nafon drer and n the DMA sheath flow loop. A computer program (wrtten n LabVIEW 7.1) was constructed n order to control the partcle spectrometer, record the breathng pattern, control valves and sensors and contnuously calculate the respratory deposton. Inlet Inhale tank 10 dm 3 DMA 2-way valve Drer CPC 1-way valves Mouthpece Exhale tank 2 dm 3 Heated area Pneumotachograph Volume >40 cm 3 Outlet Fgure 1. Schematc fgure of the flow-through system Method Charactersaton The flow-through method was charactersed wth reference to losses n the breathng system usıng a sınus wave pıston-type breath sımultor. When determnng respratory deposton, correctons must be made for partcle losses n the equpment, DFequp. DF human ( d ) = 1 C n Cex( d ) ( d ) ( 1 DF ( d ) equp (1) Where d s the partcle dameter n sze-channel and Cn and Cex denote the partcle concentraton n the nhaled and exhaled samples. Experments wth human test-persons The man part of the valdaton experments were performed n one healthy male test-person (26 years old) to mnmse physologcal varatons. The test-person followed suggested (square wave) breathng patterns on a computer screen. 301

4 To estmate the precson of the method, NaCl aerosol was nhaled n three dentcal experments (on the same day) wth breathng frequency 10 ± 0.1 mn-1, mnute volume 10 ± 0.1 L/mn. The measurement tme was 15 mnutes for each of these sessons. To valdate the senstvty of the method, deposton of NaCl was compared for three dfferent breathng patterns, 6 ± 0.5 mn-1, 10 ± 1 mn-1 and 15 ± 1 mn-1. Hydrophobc DEHS partcles were nhaled at 10 ± 1 mn-1 and 10 ± 1 L/mn. The experments were performed at a concentraton of 100,000 cm-3. The nhaled mass concentraton n experments wth human test-persons was below 100 g/m3 as determned wth combned measurements wth an APS 3321 and the SMPS. Modellng respratory deposton Respratory deposton predcted wth the ICRP 66 model (ICRP, 1994) was calculated for a healthy male, breathng through the mouth at 10 L/mn wth frequences 6, 10 and 15 mn-1. Hygroscopc growth was ncorporated n the model by assumng RH=99.5% throughout the respratory tract and mmedate growth to the equlbrum sze. Results After coverng the one way valves wth gold, the deposted number fracton ın the system decreased wth up to a factor of two and s below 6% for 20 nm partcles and approxmately 1% for nm. The respratory deposton determned wth the system was found hghly repeatable n dentcal experments wth a sngle test-person (Fgure 2). The method s clearly senstve enough to dstngush between the three dfferent breathng patterns n sngle experments (Fgure 3). The varatons are n relatvely good agreement wth the ICRP model. Fgure 4 llustrates the dfference n deposton between hygroscopc NaCl partcles and hydrophobc DEHS partcles. The agreement wth the ICRP-model s relatvely good, ndcatng that the RH s close to 99.5% n regons of the respratory tract where partcles were deposted Dry moblty dameter (nm) Fgure 2. Respratory deposton of NaCl for a sngle test-person n three dentcal experments. Breathng frequency, 10 mn-1, mnute volume 10 L/mn Error bars show a 95% confdence nterval due to countng statstcs. Dscusson and Conclusons The flow-through system performed favourable n experments wth hygroscopc aerosols n human testpersons. The precson of the method nvestgated wth dentcal experments wth sem-controlled breathng patterns resulted n varatons below 5% (DF = x ± 5%) for the man part of the sze nterval. The method s senstve enough to quantfy dfferences between breathng patterns and 302

5 Fgure 3. Respratory deposton of NaCl n a Fgure 4. Respratory deposton of hygroscopc breaths/mn ICRP, 6 breaths/mn 10 breaths/mn ICRP, 10 breaths/mn 15 breaths/mn ICRP, 15 breaths/mn Dry moblty dameter (nm) sngle test-person. Sngle measurements wth breathng frequences of 6, 10 and 15 mn-1 and an average flow-rate of 10 L/mn NaCl DEHS ICRP, hygroscopc ICRP, hydrophobc Dry moblty dameter (nm) NaCl partcles and hydrophobc DEHS partcles n a sngle test-person. Breathng frequency 10 mn- 1, mnute volume 10 L/mn. dfferences between hygroscopc and hydrophobc aerosols. Respratory deposton ncreased for all partcle szes for decreasng breathng frequency snce the deposton effcency of both dffuson and sedmentaton ncreases wth resdence tme. Our results wth NaCl and DEHS and comparsons wth the ICRP model shows that the hygroscopc partcles depost as f grown to ther equlbrum szes at RH= In concluson, the method offers a fast and relatvely smple way to determne respratory deposton n human test persons. The method performed well n precson and senstvty tests. We plan to use the descrbed method on larger groups of test-persons wth varyng respratory status n varous envronments, ncludng street canyon, fresh wood smoke and ndoor aerosols. Acknowledgements Ths study was supported by The Buldng and ts Indoor Envronment, a research school at Lund Unversty. The Research Councl for Envronment, Agrcultural Scences and Spatal Plannng (FORMAS) and the Swedsh Natonal Ar-polluton Programme (SNAP, Swedsh EPA). References 1. Chalupa D.C., Morrow P.E., Oberdorster G., Utell M.J. & Frampton M.W. (2004) Ultrafne partcle deposton n subjects wth asthma. Envronmental Health Perspectves, 112, Ezzat M., Lopez A.D., Rodgers A., Vander Hoorn S. & Murray C.J.L. (2002) Selected major rsk factors and global and regonal burden of dsease. Lancet, 360, Forsberg B., Hansson H.C., Johansson C., Areskoug H., Persson K. & Jarvholm B. (2005) Comparatve health mpact assessment of local and regonal partculate ar pollutants n Scandnava. Ambo, 34, ICRP, Internatonal Commsson on Radologcal Protecton. (1994) Human respratory tract model for radologcal protecton. [ICRP Publcaton 66]. Oxford, UK, Elsever Scence. 5. WHO Workng Group Meetng (2003) Health aspects of ar polluton wth partculate matter, ozone and ntrogen doxde. In: (ed. WHO Workng Group Meetng). World Health Organzaton, pp