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 O 3 , PM 2.5 , 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 O 3 , PM 2.5 , 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 O 3 exposures, a new active O 3 sampler was developed that uses two nitrite-coated filters to measure O 3 concentrations. Laboratory chamber tests found that the active O 3 sampler 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 O 3 sampler 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. PM 2.5 and 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 µm and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM 2.5 concentrations than those obtained by the collocated 12-hr PM 2.5 PEM 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 R 2 values 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 PM 2.5 exposures. 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)].

Particulate matter and polycyclic aromatic hydrocarbon concentrations in indoor and outdoor microenvironments in Boston, Massachusetts

“…In a linear model, 30-min average DustTrak concentrations were 2.8 times TEOM concentrations, with an intercept near 0 and an R 2 of 0.93 ( n= 46 ). Although it has been documented that the TEOM loses a significant fraction of semivolatile particulate matter ( Allen et al, 1997 ), this fact cannot explain the magnitude of the difference or the similar differences documented with gravimetric methods elsewhere ( Chang et al, 2001 ). A consistent multiplicative relationship implies that indooroutdoor ratios and relative comparisons between microenvironments might not be drastically affected by the sampling bias, but that our PM 2.5 measurements may need to be modified before they could be used in personal exposure models.…”

Influence of traffic patterns on particulate matter and polycyclic aromatic hydrocarbon concentrations in Roxbury, Massachusetts

“…It should be noted that past studies have found that the DustTrak overstates ambient concentrations when not calibrated to the specific ambient particles being measured, but that the bias is a consistent multiplicative factor. For example, one study (Chang et al, 2001) determined that PM 2.5 concentrations from a DustTrak were a factor of 2.1 greater than concentrations from an integrated personal exposure monitor during the summer, with an R 2 of 0.87. Similarly, another study (Levy et al, 2002) found a factor of 2.8 difference between DustTrak and TEOM measurements, with an R 2 of 0.93.…”

Air curtain as a barrier against pollutants in cultural heritage: a case study

“…8520 in conformity with technical requirements of the V annex of the Italian Environmental Ministry Decree 23/11/1994. Ultra-fine particulate PM 2.5 has been detected with PM 2.5 EN LVS equipment (see figure 1), according to the En 12341 regulation [4,5] and Italian Law Decree n° 60 02/04/2002; the suction air flow rate is equal to 38 litres/minute and the monitoring period range is between 12 and 24 hours.…”

“…For a better comprehension of the data, in bold are reported those values (coming from the mean of the results of the three monitorings) exceeding the comfort and health limits deduced from the following Italian regulations: T, UR Technical Regulation UNI 10339 CO, CO 2 Italian Ministry Decree n. 159 25/11/1994 PM 10 Italian Ministry Decree n. 159 25/11/1994 PM 2,5 Environmental Ministry Decree n. 60 02/04/2002 Using PM 10 concentration as a performance indicator of the system efficiency, is it possible to underline that 55µg/m 3 of particulates, exceeding the external value of 60µg/m 3 , are introduced by the visitors in the first room before the air curtain; only 16 µg/m 3 pass through the air curtain in the antechapel room with an abatement factor of about 71%, while almost 85% of this PM 10 (14 µg/m 3 ) pass from the antechapel into the frescoes chapel.…”