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Measuring occupational dust exposure with a passive sampler
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Mätning av dammexponering i arbetslivet med en passiv provtagare (Swedish)
Abstract [en]

Objectives: In a working environment it is important to measure dust exposure to evaluate possible health issues. Passive sampling could be an alternative to active sampling with pumps when measuring occupational dust exposure. One passive sampler is the University of North Carolina passive aerosol sampler (UNC sampler). Promising results for the applicability of this type of passive sampler have been shown for particles above 2.5 μm, but indicate large underestimations for PM2.5. The overall purpose was to develop more knowledge about the UNC sampler and the possibility of using it for personal sampling of occupational dust exposure. Specific aims were to: evaluate and possibly improve the UNC sampler for stationary sampling in a working environment and compare the UNC sampler with commonly used aerosol sampling methods; characterise the impairment in performance of the UNC sampler concentrations when decreasing the number of images in order to achieve lowered costs and decreased analysis time, and; establish if the UNC sampler could be used for personal sampling in the working environment.

Methods: All sample collection in this thesis was performed in an open pit mine. For stationary sampling UNC samplers, impactors (PM10 and PM2.5), respirable cyclones, and an aerodynamic particle sizer were used. For personal sampling UNC samplers and respirable cyclones were used. The analysis of the UNC sampler consisted of two parts, the microscopic imaging of the deposited particles and the analysis model for calculations of mass concentration.

Results: In the first pilot study the UNC sampler with its original analysis model was used. Compared to PM10 impactor concentrations the UNC sampler showed 58% of the impactor results and 35% of PM2.5 impactor results. The second study showed that a new analysis model and use of higher microscopy resolution led to no underestimation compared to PM2.5 impactors, while PM10 improved but not to the same extent. A higher precision was also achieved compared to the respirable cyclone (intraclass correlation: 0.51 versus 0.24). When UNC sampler particle size distributions were compared to aerodynamic particle sizer data, they showed similar distributions for the new analysis model, but deviating distributions for the original analysis model. In the third study the number of images needed from the microscopic imaging process was reduced. Reducing the number of images analysed from 60 to 10 increased the coefficient of variation from 36% to 37% for respirable fraction. Finally, the UNC sampler was used for personal sampling in a working environment for the first time. Again, the particle size distribution of the new UNC sampler analysis model was reasonable, while the distribution of the original model was not. There were almost exclusively particles of mineral origin on the UNC sampler, but compared to the respirable cyclone, the UNC sampler overestimated the particle concentrations approximately 30 times.

Conclusions: The new analysis model for the UNC sampler enables stationary passive sampling of dust exposure of mineral character. Quicker microscopic image analysis, by reducing the number of images for mass concentration calculations to ten, results in a negligible loss in precision. Personal sampling with the UNC sampler showed deposited particles of reasonable size distribution and obviously originating from the working environment, but with severe overestimation of the mass concentration. Thus, the UNC sampler with the new analysis model can be used for stationary sampling in a mine, but is not yet ready for personal sampling.

Abstract [sv]

Vi utsätts för damm hela tiden, däremot är inte allt damm skadligt. Skadligt damm som vi utsätts för på grund av arbetet är viktigt att mäta för att utreda olika hälsorisker. För att mäta damm i arbetsmiljön används idag pumpad provtagning. Pumpad provtagning innebär att en avskiljare suger in damm, med hjälp av en pump, på ett filter som vägs. Två exempel på avskiljare som gör att partiklar av intresse samlas upp är en impaktor och en cyklon. En impaktor fungerar på så sätt att dammpartiklarna som är för stora krockar med en yta, medan resten landar på filtret. Cyklonen fungerar nästan på samma sätt, men den baseras på en luftvirvel som skiljer på dammpartiklarna utifrån storlek. Ett alternativ till pumpad provtagning av damm i arbetsmiljön skulle kunna vara passiv provtagning. Passiv provtagning innebär att en strömkälla inte behövs för att provta. En specifik passiv provtagare, University of North Carolina passiv partikelprovtagare, studerades. Lovande resultat har redan setts med den passiva provtagaren för partiklar större än 2.5 μm, men den har visat alltför låga koncentrationer för de lägre partikelstorlekarna. Målet var att inhämta mer kunskap om denna passiva provtagare och undersöka om den kan användas för personburen provtagning i arbetsmiljön. Arbetsmiljön som valdes för att undersöka den passiva provtagaren i var en gruva (dagbrott). Då provtagaren aldrig använts i gruvan tidigare togs även impaktorer, cykloner och andra typer av provtagare med som det redan finns kunskap om och som redan blivit testade. Mätningarna utfördes på två olika vis, både på olika platser i gruvan och även på olika personer. För att utvärdera resultatet av den passiva provtagaren tas bilder på dammet med ett avancerat mikroskop. Informationen från bilderna görs sedan om till koncentrationen av dammet för att kunna jämföra detta med de andra provtagarna.Efter de första mätningarna visade den passiva provtagaren lägre koncentrationer jämfört med impaktorerna. Då tidigare studier visat att den passiva provtagaren stämde bra överens för större partiklar gjordes fler mätningar. Från den andra vändan av mätningar upptäcktes återigen samma fenomen. Det som inte hade tagits hänsyn till i teorin för den passiva provtagaren var att den fungerar annorlunda då det är vindstilla. Överallt i gruvan där det hade mätts var det vindstilla. Efter att ha ändrat modellen till att ta hänsyn till att det var vindstilla visade det sig att den passiva provtagaren stämde bättre överens med impaktorerna. Den passivaprovtagarens massfördelning (förhållandet mellan små och stora partiklar) visade dessutom samma form som jämförelseinstrumentets. Vid den personburna provtagningen (med den passiva provtagaren) mättes damm från arbetsmiljön och inte sådant som kom från personen. Den nya modellen visade sig även här ge en förväntad massfördelning, medan den gamla modellen inte gjorde det. Den gamla modellen var mer fördelaktig för de största partiklarna och fick därför en skev fördelning. Den passiva provtagaren uppmätte dock mycket högre koncentrationer jämfört med cyklonen.Om hänsyn tas till att modellen måste ändras då det är vindstilla kan den passiva provtagaren användas för platsmätningar i gruvmiljön. För personburen provtagning mätte den passiva provtagaren dammet från arbetsmiljön och inte till exempel hud eller textilier. Den visade dock mycket högre koncentrationer av damm än jämförelseprovtagaren. Således kan den passiva provtagaren användas för platsmätningar i gruvmiljön, men den är ännu inte redo för personburen provtagning.

Place, publisher, year, edition, pages
Umeå: Umeå university , 2018. , p. 58
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1946
Keywords [en]
dust particles, mineral, PM10, PM2.5, respirable fraction, UNC passive aerosol sampler, working environment
National Category
Occupational Health and Environmental Health
Identifiers
URN: urn:nbn:se:umu:diva-145704ISBN: 978-91-7601-834-7 (print)OAI: oai:DiVA.org:umu-145704DiVA, id: diva2:1190484
Public defence
2018-04-13, Triple Helix, Samverkanshuset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2018-03-23 Created: 2018-03-14 Last updated: 2018-06-09Bibliographically approved
List of papers
1. A pilot study: the UNC passive aerosol sampler in a working environment
Open this publication in new window or tab >>A pilot study: the UNC passive aerosol sampler in a working environment
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2017 (English)In: Annals of Work Exposures and Health, ISSN 2398-7308, Vol. 61, no 8, p. 1029-1034Article in journal (Refereed) Published
Abstract [en]

Objectives: Dust is generally sampled on a filter using air pumps, but passive sampling could be a cost-effective alternative. One promising passive sampler is the University of North Carolina passive aerosol sampler (UNC sampler). The aim of this study is to characterize and compare the UNC sampler’s performance with PM10 and PM2.5 impactors in a working environment.

Methods: Area sampling was carried out at different mining locations using UNC samplers in parallel with PM2.5 and PM10 impactors. Two different collection surfaces, polycarbonate (PC) and carbon tabs (CT), were employed for the UNC sampling. Sampling was carried out for 4–25 hours.

Results: The UNC samplers underestimated the concentrations compared to PM10 and PM2.5 impactor data. At the location with the highest aerosol concentration, the time-averaged mean of PC showed 24% and CT 35% of the impactor result for PM2.5. For PM10, it was 39% with PC and 58% with CT. Sample blank values differed between PC and CT. For PM2.5, PC blank values were ~7 times higher than those of CT, but only 1.8 times higher for PM10. The blank variations were larger for PC than for CT.

Conclusions: Particle mass concentrations appear to be underestimated by the UNC sampler compared to impactors, more so for PM2.5 than for PM10. CT may be preferred as a collection surface because the blank values were lower and less variable than for PC. Future validations in the working environment should include respirable dust sampling.

Place, publisher, year, edition, pages
Oxford University Press, 2017
Keywords
inorganic dust, PM2.5, PM10, scanning electron microscopy, UNC passive aerosol sampler, working environment
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:umu:diva-140539 (URN)10.1093/annweh/wxx067 (DOI)000417608500013 ()29028256 (PubMedID)
Available from: 2017-10-13 Created: 2017-10-13 Last updated: 2018-06-09Bibliographically approved
2. Improving the UNC passive aerosol sampler model based on comparison with commonly used aerosol sampling methods
Open this publication in new window or tab >>Improving the UNC passive aerosol sampler model based on comparison with commonly used aerosol sampling methods
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2018 (English)In: Annals of Work Exposures and Health, ISSN 2398-7308, Vol. 62, no 3, p. 328-338Article in journal (Refereed) Published
Abstract [en]

Objectives: In an occupational environment, passive sampling could be an alternative to active sampling with pumps for sampling of dust. One passive sampler is the University of North Carolina passive aerosol sampler (UNC sampler). It is often analysed by microscopic imaging. Promising results have been shown for particles above 2.5 µm, but indicate large underestimations for PM2.5. The aim of this study was to evaluate, and possibly improve, the UNC sampler for stationary sampling in a working environment.

Methods: Sampling was carried out at 8-h intervals during 24 h in four locations in an open pit mine with UNC samplers, respirable cyclones, PM10 and PM2.5 impactors, and an aerodynamic particle sizer (APS). The wind was minimal. For quantification, two modifications of the UNC sampler analysis model, UNC sampler with hybrid model and UNC sampler with area factor, were compared with the original one, UNC sampler with mesh factor derived from wind tunnel experiments. The effect of increased resolution for the microscopic imaging was examined.

Results: Use of the area factor and a higher resolution eliminated the underestimation for PM10 and PM2.5. The model with area factor had the overall lowest deviation versus the impactor and the cyclone. The intraclass correlation (ICC) showed that the UNC sampler had a higher precision and better ability to distinguish between different exposure levels compared to the cyclone (ICC: 0.51 versus 0.24), but lower precision compared to the impactor (PM10: 0.79 versus 0.99; PM2.5: 0.30 versus 0.45). The particle size distributions as calculated from the different UNC sampler analysis models were visually compared with the distributions determined by APS. The distributions were obviously different when the UNC sampler with mesh factor was used but came to a reasonable agreement when the area factor was used.

Conclusions: High resolution combined with a factor based on area only, results in no underestimation of small particles compared to impactors and cyclones and a better agreement with the APS’s particle size distributions. The UNC sampler had lower precision than the impactors, but higher than the respirable cyclone. The UNC sampler with area factor could be used for PM2.5, PM10 and respirable fraction measurements in this working environment without wind.

Place, publisher, year, edition, pages
Oxford University Press, 2018
Keywords
inorganic dust, mesh factor, PM10, PM2.5, respirable fraction, UNC passive aerosol sampler, working environment
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:umu:diva-145698 (URN)10.1093/annweh/wxx110 (DOI)000432804600008 ()29300818 (PubMedID)
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-06-26Bibliographically approved
3. Choosing the number of images and image position when analysing the UNC passive aerosol sampler for occupational exposure assessment
Open this publication in new window or tab >>Choosing the number of images and image position when analysing the UNC passive aerosol sampler for occupational exposure assessment
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(English)Manuscript (preprint) (Other academic)
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:umu:diva-145702 (URN)
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-06-09
4. Passive personal sampling of dust in a working environment: a first study
Open this publication in new window or tab >>Passive personal sampling of dust in a working environment: a first study
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(English)Manuscript (preprint) (Other academic)
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:umu:diva-145703 (URN)
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-06-09

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