Laboratory and field evaluation of real-time and near real-time PM2.5 smoke monitors.

Increases in large wildfire frequency and intensity and a longer fire season in the western United States are resulting in a significant increase in air pollution, including concentrations of PM2.5 (particulate matter <2.5 µm in aerodynamic diameter) that pose significant health risks to nearby communities. During wildfires, government agencies monitor PM2.5 mass concentrations providing information and actions needed to protect affected communities; this requires continuously measuring instruments. This study assessed the performance of seven candidate instruments: (1) Met One Environmental beta attenuation monitor (EBAM), (2) Met One ES model 642 (ES642), (3) Grimm Environmental Dust Monitor 164 (EDM), (4) Thermo ADR 1500 (ADR), (5) TSI DRX model 8543 (DRX), (6) Dylos 1700 (Dylos), and (7) Purple Air II (PA-II) in comparison with a BAM 1020 (BAM) reference instrument. With the exception of the EBAM, all candidates use light scattering to determine PM2.5 mass concentrations. Our comparison study included environmental chamber and field components, with two of each candidate instrument operating next to the reference instrument. The chamber component involved 6 days of comparisons for biomass combustion emissions. The field component involved operating all instruments in an air monitoring station for 39.5 days with hourly average relative humidity (RH) ranging from 19% to 98%. Goals were to assess instrument precision and accuracy and effects of RH, elemental carbon (EC), and organic carbon (OC) concentrations. All replicate candidate instruments showed high hourly correlations (R2 ≥ 0.80) and higher daily average correlations (R2 ≥ 0.90), where all instruments correlated well (R2 ≥ 0.80) with the reference. The DRX and Purple Air overestimated PM2.5 mass concentrations by a factor of ~two. Differences between candidates and reference were more pronounced at higher PM2.5 concentrations. All optical instruments were affected by high RH and by the EC/OC ratio. Equations to convert candidate instruments data to FEM BAM type data are provided to enhance the usability of data from candidate instruments.Implications: This study tested the performance of seven candidate PM2.5 mass concentration measuring instruments in two settings - environmental chamber and field. The instruments were tested to determine their suitability for use during biomass combustion events and the effects of RH, PM mass concentrations, and concentrations of EC and OC on their performance. The accuracy and precision of each monitor and effect of RH, PM concentration, EC and OC concentrations are varied. The data show that most of these candidate instruments are suitable for measuring PM2.5 concentration during biomass combustions with a proper correction factor for each instrument type.

Deriving fuel-based emission factor thresholds to interpret heavy-duty vehicle roadside plume measurements.

Remote sensing devices have been used for decades to measure gaseous emissions from individual vehicles at the roadside. Systems have also been developed that entrain diluted exhaust and can also measure particulate matter (PM) emissions. In 2015, the California Air Resources Board (CARB) reported that 8% of in-field diesel particulate filters (DPF) on heavy-duty (HD) vehicles were malfunctioning and emitted about 70% of total diesel PM emissions from the DPF-equipped fleet. A new high-emitter problem in the heavy-duty vehicle fleet had emerged. Roadside exhaust plume measurements reflect a snapshot of real-world operation, typically lasting several seconds. In order to relate roadside plume measurements to laboratory emission tests, we analyzed carbon dioxide (CO2), oxides of nitrogen (NOX), and PM emissions collected from four HD vehicles during several driving cycles on a chassis dynamometer. We examined the fuel-based emission factors corresponding to possible exceedances of emission standards as a function of vehicle power. Our analysis suggests that a typical HD vehicle will exceed the model year (MY) 2010 emission standards (of 0.2 g NOX/bhp-hr and 0.01 g PM/bhp-hr) by three times when fuel-based emission factors are 9.3 g NOX/kg fuel and 0.11 g PM/kg using the roadside plume measurement approach. Reported limits correspond to 99% confidence levels, which were calculated using the detection uncertainty of emissions analyzers, accuracy of vehicle power calculations, and actual emissions variability of fixed operational parameters. The PM threshold was determined for acceleration events between 0.47 and 1.4 mph/sec only, and the NOX threshold was derived from measurements where after-treatment temperature was above 200°C. Anticipating a growing interest in real-world driving emissions, widespread implementation of roadside exhaust plume measurements as a compliment to in-use vehicle programs may benefit from expanding this analysis to a larger sample of in-use HD vehicles. IMPLICATIONS: Regulatory agencies, civil society, and the public at large have a growing interest in vehicle emission compliance in the real world. Leveraging roadside plume measurements to identify vehicles with malfunctioning emission control systems is emerging as a viable new and useful method to assess in-use performance. This work proposes fuel-based emission factor thresholds for PM and NOx that signify exceedances of emission standards on a work-specific basis by analyzing real-time emissions in the laboratory. These thresholds could be used to prescreen vehicles before roadside enforcement inspection or other inquiry, enhance and further develop emission inventories, and potentially develop new requirements for heavy-duty inspection and maintenance (I/M) programs, including but not limited to identifying vehicles for further testing.

Seasonal influences on CAPs exposures: differential responses in platelet activation, serum cytokines and xenobiotic gene expression.

Increasing evidence suggests a role for a systemic pro-coagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter (PM). We evaluated platelet activation, systemic cytokines and pulmonary gene expression in mice exposed to concentrated ambient particulate matter (CAPs) in the summer of 2008 (S08) and winter of 2009 (W09) from the San Joaquin Valley of California, a region with severe PM pollution episodes. Additionally, we characterized the PM from both exposures including organic compounds, metals, and polycyclic aromatic hydrocarbons. Mice were exposed to an average of 39.01 µg/m(3) of CAPs in the winter and 21.7 µg/m3 CAPs in the summer, in a size range less than 2.5 µm for 6 h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, CD41, P-selectin and lysosomal associated membrane protein-1 (LAMP-1) expression. Platelets from W09 CAPs-exposed animals had a greater response to thrombin stimulation than platelets from S08 CAPs-exposed animals. Serum cytokines were analyzed by bead based immunologic assays. W09 CAPs-exposed mice had elevations in IL-2, MIP-1α, and TNFα. Laser capture microdissection (LCM) of pulmonary vasculature, parenchyma and airways all showed increases in CYP1a1 gene expression. Pulmonary vasculature showed increased expression of ICAM-1 and Nox-2. Our findings demonstrate that W09 CAPs exposure generated a greater systemic pro-inflammatory and pro-coagulant response to inhalation of environmentally derived fine and ultrafine PM. Changes in platelet responsiveness to agonists, seen in both exposures, strongly suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.

Influence of season and location on pulmonary response to California's San Joaquin Valley airborne particulate matter.

Season and location have documented impacts on particulate matter (PM)-induced morbidity and mortality. Seasonal and regional influences on the physical and chemical properties of PM2.5 (also known as fine/ultrafine PM) contribute to differences in exposure burden and adverse respiratory health outcomes experienced in California's San Joaquin Valley (SJV), which ranks among the worst in the nation for PM pollution. Current regulations are driven by the association between mass concentrations and adverse health outcomes. However, this association is difficult to reproduce in toxicological studies and suggests a role for other parameters, such as chemical composition, involved in PM-induced adverse pulmonary health effects. Pulmonary toxicity of summer/winter and rural/urban SJV PM was evaluated given the unique geography, metereology and sources of the region. Healthy juvenile male mice inhaled summer/winter and urban/rural concentrated ambient PM (CAP) or ambient PM for 6 h/d for 10 d, and pulmonary inflammatory responses were measured 48 h postexposure. Exposure concentrations ranged from 10 to 20 µg/m³ for ambient air control mice and from 86 to 284 µg/m³. Mice exposed to rural but not urban CAP, displayed significant neutrophil influx that was more than 50-fold greater than control levels, which ranged from 21 to 60 neutrophils/ml for all experiments. Pulmonary neutrophilic inflammation was measured despite lower CAP concentrations in the rural compared to the urban location and in the absence of cytotoxicity, oxidative stress, or elevations in cytokine and chemokines expression. Further, the inflammatory responses induced by rural winter CAP were associated with the highest levels of organic carbon (OC) and nitrates (NO3⁻). Evidence indicates that regional/seasonal influences on PM chemical composition rather than PM mass may be associated with increased PM-induced adverse health effects.