Evaluation of Variability in the Ambient PM2.5 Concentrations from FEM and FRM-like Measurements for Exposure Estimates

Abstract

This study aims to evaluate the variability in ambient fine particulate matter (PM2.5) concentrations obtained from the federal equivalent method (FEM) and federal reference method (FRM)-like measurements at the national air quality monitoring stations (AQMSs) for exposure estimates and to examine the effect of environmental factors and sampling site characteristics affecting the spatial and temporal variations in PM2.5 concentrations. A mixed-effects model was used to evaluate the temporal and spatial variability in daily and annual PM2.5 concentrations during 20142017 at 16 AQMSs in the Big Taipei City, Taiwan. The mean FEM PM2.5 concentrations were ~30% higher than the FRM-like PM2.5 concentrations. The FRM-like PM2.5 concentrations obtained by applying the calibration procedures presented a negligible betweensite variability. The daily FEM PM2.5 concentrations were dominated by the within-site variability (~90%), whereas the annual concentrations were reasonably attributable to the between-site variability (47.8%). Ambient PM2.5 was mainly affected by the gaseous pollutants (such as NO2, O3, and SO2), accounting for 45.8% and 26.8% of the within-site and between-site variability in concentrations, respectively. The FEM measurements rather than the FRM-like measurements at the AQMSs could provide a higher between-site variability for exposure estimates of PM2.5 in the epidemiological studies.

Enhancing PM2.5 Measurement Accuracy: Insights from Environmental Factors and BAM-Light Scattering Device Correlation

“…While FRM, known for its accuracy, employs gravimetric measures for filter-based measurements, it provides average concentrations over 24 hours [7]. FEM, less accurate but offering hourly measurements through methods like beta attenuation monitoring (BAM) or tapered element oscillating microbalances (TEOM) [8], adheres to standards outlined in 40 Code of Federal Regulations Part 50 for precision under changing environmental conditions. These methods are adopted globally, including by the US Environment Protection Agency (EPA) and government agencies in China, Japan, Europe, and Korea [9].…”