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Improving the UNC Passive Aerosol Sampler Model Based on Comparison with Commonly Used Aerosol Sampling Methods.

ABSTRACT: 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.

SUBMITTER: Shirdel M

PROVIDER: S-EPMC5873525 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Improving the UNC Passive Aerosol Sampler Model Based on Comparison with Commonly Used Aerosol Sampling Methods.

Shirdel Mariam M Andersson Britt M BM Bergdahl Ingvar A IA Sommar Johan N JN Wingfors Håkan H Liljelind Ingrid E IE

Annals of work exposures and health 20180301 3

<h4>Objectives</h4>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 w ...[more]

PMID: 29300818

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Project description:We provide a narrative review on the published peer-reviewed scientific literature reporting sampler efficiency, performance and comparison studies (where two or more samplers have been assessed) in laboratory settings published between 1994 and 2021 (27 year period). This review is a follow-up to our narrative review on the published peer-reviewed scientific literature reporting sampler comparison in workplace settings. Search terms were developed for Web of Science and PubMed bibliographic databases. The retrieved articles were then screened for relevance, with those studies meeting the inclusion criteria being taken forward to data extraction (25 studies). The most common fraction assessed has been the inhalable fraction, with the IOM sampler being the most studied inhalable sampler and the SKC Aluminium cyclone being the most studied respirable sampler from the identified relevant articles. The most common aerosol used has been aluminium oxide. It was evident that standardisation for these sampler performance experiments is lacking. It was not possible to identify any discernible trends for the performance of samplers when assessed with different aerosols. The need for more detailed and informative data sharing from authors is highlighted. This includes provision of clear identifiable information on the samplers used for testing, sampler flow rates (both manufacturer and those actually used in the study, with an explanation given of any differences), detailed information on the test aerosols used and the sampler substrate materials used. An identified gap in the literature is the potential to perform studies aimed at revaluating the performance of samplers to allow any longer-term temporal changes in performance to be assessed. One approach in advancing the field is to produce an updated protocol for the laboratory testing of samplers. This updated protocol would be beneficial for both the research and occupational hygiene community and would allow harmonised assessment and reporting of sampler comparison studies.

Project description:From June 2013 to March 2015, in total 41 passive sampler deployments of 2 wk duration each were conducted at 17 sites in South Philadelphia, PA, with results for benzene discussed here. Complementary time-resolved measurements with lower cost prototype fenceline sensors and an open-path ultraviolet differential optical absorption spectrometer were also conducted. Minimum passive sampler benzene concentrations for each sampling period ranged from 0.08 ppbv to 0.65 ppbv, with a mean of 0.25 ppbv, and were negatively correlated with ambient temperature (-0.01 ppbv/°C, R2 = 0.68). Co-deployed duplicate passive sampler pairs (N = 609) demonstrated good precision with an average and maximum percent difference of 1.5% and 34%, respectively. A group of passive samplers located within 50 m of a refinery fenceline had a study mean benzene concentration of 1.22 ppbv, whereas a group of samplers located in communities >1 km distant from facilities had a mean of 0.29 ppbv. The difference in the means of these groups was statistically significant at the 95% confidence level (p < 0.001). A decreasing gradient in benzene concentrations moving away from the facilities was observed, as was a significant period-to-period variation. The highest recorded 2-wk average benzene concentration for the fenceline group was 3.11 ppbv. During this period, time-resolved data from the prototype sensors and the open-path spectrometer detected a benzene signal from the west on one day in particular, with the highest 5-min path-averaged benzene concentration measured at 24 ppbv. Implications:Using a variation of EPA's passive sampler refinery fenceline monitoring method, coupled with time-resolved measurements, a multiyear study in South Philadelphia informed benzene concentrations near facilities and in communities. The combination of measurement strategies can assist facilities in identification and mitigation of emissions from fugitive sources and improve information on air quality complex air sheds.

Dataset Information

Improving the UNC Passive Aerosol Sampler Model Based on Comparison with Commonly Used Aerosol Sampling Methods.

Publications

Improving the UNC Passive Aerosol Sampler Model Based on Comparison with Commonly Used Aerosol Sampling Methods.

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