title: Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O3, PM25, and CO.
abstract: While researchers have linked acute (less than 12-hr) ambient O3, PM25, and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the "roll-around" system (RAS), which was developed to measure 1-hr O3, PM25, and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999. To measure 1-hr O3exposures, a new active O3sampler was developed that uses two nitrite-coated filters to measure O3concentrations. Laboratory chamber tests found that the active O3sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O3sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and ~16 ppb-hr for the field comparison tests. PM2.5and CO concentrations were measured using modified continuous monitors-the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 um and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM2.5concentrations than those obtained by the collocated 12-hr PM2 5PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R2values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM2 5exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [~1 part per million (ppm)].
authors.affiliation: a Department of Environmental Health , Harvard School of Public Health , Boston , Massachusetts , USA.
authors.forename: Li-Te
authors.initials: LT
authors.lastname: Chang
authors.affiliation: a Department of Environmental Health , Harvard School of Public Health , Boston , Massachusetts , USA.
authors.forename: Helen H
authors.initials: HH
authors.lastname: Suh
authors.affiliation: a Department of Environmental Health , Harvard School of Public Health , Boston , Massachusetts , USA.
authors.forename: Jack M
authors.initials: JM
authors.lastname: Wolfson
authors.affiliation: a Department of Environmental Health , Harvard School of Public Health , Boston , Massachusetts , USA.
authors.forename: Kshipra
authors.initials: K
authors.lastname: Misra
authors.affiliation: a Department of Environmental Health , Harvard School of Public Health , Boston , Massachusetts , USA.
authors.forename: George A
authors.initials: GA
authors.lastname: Allen
authors.affiliation: b Department of Biostatistics , Dana-Farber Cancer Institute, and Harvard School of Public Health , Boston , Massachusetts , USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Catalano
authors.affiliation: c Harvard School of Public Health , Massachusetts , USA.
authors.forename: Petros
authors.initials: P
authors.lastname: Koutrakis