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Evaluation and quality control of personal nephelometers in indoor, outdoor and personal environments

Journal of Exposure Science & Environmental Epidemiology volume 15, pages 99–110 (2005)Cite this article

Abstract

Personal nephelometers provide useful real-time measurements of airborne particulate matter (PM). Recent studies have applied this tool to assess personal exposures and related health effects. However, a thorough quality control (QC) procedure for data collected from such a device in a large-scale exposure assessment study is lacking. We have evaluated the performance of a personal nephelometer (personal DataRAM or pDR) in the field. We present here a series of post hoc QC procedures for improving the quality of the pDR data. The correlations and the ratios between the pDRs and the collocated gravimetric measurements were used as indices of the pDR data quality. The pDR was operated in four modes: passive (no pump), active (with personal sampling pumps), active with a heated inlet, and a humidistat. The pDRs were worn by 21 asthmatic children, placed at their residences indoors and outdoors, as well as at a central site. All fixed-site pDRs were collocated with Harvard Impactors for PM2.5 (HI2.5). By examining the differences between the time-weighted average concentrations calculated from the real-time pDRs’ readings and recorded internally by the pDRs, we identified 9.1% of the pDRs’ measurements suffered from negative drifts. By comparing the pDRs’ daily base level with the HI2.5 measurements, we identified 5.7% of the pDRs’ measurements suffered from positive drifts. High relative humidity (RH) affected outdoor pDR measurements, even when a heater was used. Results from a series of chamber experiments suggest that the heated air stream cooled significantly after leaving the heater and entering the pDR light-scattering chamber. An RH correction equation was applied to the pDR measurements to remove the RH effect. The final R2 values between the fixed-site pDRs and the collocated HI2.5 measurements ranged between 0.53 and 0.72. We concluded that with a carefully developed QC procedure, personal nephelometers can provide high-quality data for assessing PM exposures on subjects and at fixed locations. We also recommend that outdoor pDRs be operated in the active mode without a heater and that the RH effect be corrected with an RH correction equation.

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Acknowledgements

This study was funded by the NIH/NIEHS Grant ES-06214 and EPA Northwest Research Center for Particulate Air Pollution and Health Grant R827355. We also thank Dr. Timothy Larson for his insightful comments.

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Authors and Affiliations

  1. Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, 98195, USA

    Chang-Fu Wu & L-J Sally Liu

  2. Epidemiology Division, Department of Medicine, University of California at Irvine, Irvine, CA, 92697, USA

    Ralph J Delfino & Joshua N Floro

  3. Division of Occupational and Environmental Health, San Diego State University, San Diego, CA, 92182, USA

    Behzad S Samimi & Penelope J E Quintana

  4. Department of Community and Environmental Medicine, University of California at Irvine, Irvine, CA, 92697, USA

    Michael T Kleinman

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  1. Chang-Fu Wu
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  2. Ralph J Delfino
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  3. Joshua N Floro
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  4. Behzad S Samimi
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  5. Penelope J E Quintana
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  7. L-J Sally Liu
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Correspondence to Chang-Fu Wu.

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Wu, CF., Delfino, R., Floro, J. et al. Evaluation and quality control of personal nephelometers in indoor, outdoor and personal environments. J Expo Sci Environ Epidemiol 15, 99–110 (2005). https://doi.org/10.1038/sj.jea.7500351

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  • DOI: https://doi.org/10.1038/sj.jea.7500351

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