Article

Journal of Exposure Science and Environmental Epidemiology (2011) 21, 49–64; doi:10.1038/jes.2010.15; published online 26 May 2010

Validation of continuous particle monitors for personal, indoor, and outdoor exposures

Lance A Wallacea, Amanda J Wheelerb, Jill Kearneyb, Keith Van Ryswykb, Hongyu Youb, Ryan H Kulkab, Pat E Rasmussenc, Jeff R Brookd and Xiaohong Xue

  1. a11568 Woodhollow Ct, Reston, Virginia 20191, USA
  2. bAir Health Science Division, Health Canada, 269 Laurier Avenue West, Ottawa, Ontario K1A 0K9, Canada
  3. cExposures and Biomonitoring Division, Health Canada, 50 Colombine Driveway, Ottawa, Ontario K1A 0K9, Canada
  4. dProcess Research, Environment Canada, 4905 Dufferin Street, Downsview, Ontario M3H RT4, Canada
  5. eDepartment of Civil and Environmental Engineering, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada

Correspondence: Dr Lance A. Wallace, 11568 Woodhollow Ct, Reston, VA 20191, USA. Tel.: +703 391 8027; Fax: +703 860 0678; E-mail: lwallace73@gmail.com

Received 15 November 2009; Accepted 8 February 2010; Published online 26 May 2010.

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Abstract

Continuous monitors can be used to supplement traditional filter-based methods of determining personal exposure to air pollutants. They have the advantages of being able to identify nearby sources and detect temporal changes on a time scale of a few minutes. The Windsor Ontario Exposure Assessment Study (WOEAS) adopted an approach of using multiple continuous monitors to measure indoor, outdoor (near-residential) and personal exposures to PM2.5, ultrafine particles and black carbon. About 48 adults and households were sampled for five consecutive 24-h periods in summer and winter 2005, and another 48 asthmatic children for five consecutive 24-h periods in summer and winter 2006. This article addresses the laboratory and field validation of these continuous monitors. A companion article (Wheeler et al., 2010) provides similar analyses for the 24-h integrated methods, as well as providing an overview of the objectives and study design. The four continuous monitors were the DustTrak (Model 8520, TSI, St. Paul, MN, USA) and personal DataRAM (pDR) (ThermoScientific, Waltham, MA, USA) for PM2.5; the P-Trak (Model 8525, TSI) for ultrafine particles; and the Aethalometer (AE-42, Magee Scientific, Berkeley, CA, USA) for black carbon (BC). All monitors were tested in multiple co-location studies involving as many as 16 monitors of a given type to determine their limits of detection as well as bias and precision. The effect of concentration and electronic drift on bias and precision were determined from both the collocated studies and the full field study. The effect of rapid changes in environmental conditions on switching an instrument from indoor to outdoor sampling was also studied. The use of multiple instruments for outdoor sampling was valuable in identifying occasional poor performance by one instrument and in better determining local contributions to the spatial variation of particulate pollution. Both the DustTrak and pDR were shown to be in reasonable agreement (R2 of 90 and 70%, respectively) with the gravimetric PM2.5 method. Both instruments had limits of detection of about 5μg/m3. The DustTrak and pDR had multiplicative biases of about 2.5 and 1.6, respectively, compared with the gravimetric samplers. However, their average bias-corrected precisions were <10%, indicating that a proper correction for bias would bring them into very good agreement with standard methods. Although no standard methods exist to establish the bias of the Aethalometer and P-Trak, the precision was within 20% for the Aethalometer and within 10% for the P-Trak. These findings suggest that all four instruments can supply useful information in environmental studies.

Keywords:

personal exposure; particulate matter; inhalation exposure; environmental monitoring