Sina Hasheminassab

Long-term source apportionment of ambient fine particulate matter (PM2.5) in the Los Angeles Basin: A focus on emissions reduction from vehicular sources

Positive Matrix Factorization (PMF) was utilized to quantify sources of ambient PM2.5 in central Los Angeles (LA) and Rubidoux, using the Speciation Trends Network data, collected between 2002 and 2013. Vehicular emissions (including gasoline and diesel vehicles) were the second major contributor to PM2.5, following secondary aerosols, with about 20% contribution to total mass in both sites. Starting in 2007, several major federal, state, and local regulations on vehicular emissions were implemented. To assess the effect of these regulations, daily-resolved vehicular source contributions from 2002 to 2006 were pooled together and compared to the combination of 2008 to 2012 datasets. Compared to the 2002-2006 dataset, the median values of vehicular emissions in 2008-2012 statistically significantly decreased by 24 and 21% in LA and Rubidoux, respectively. These reductions were noted despite an overall increase or similarity in the median values of the daily flow of vehicles after 2007, at the sites.

Seasonal and spatial variability in chemical composition and mass closure of ambient ultrafine particles in the megacity of Los Angeles

Emerging toxicological research has shown that ultrafine particles (UFP, dp < 0.1–0.2 μm) may be more potent than coarse or fine particulate matter. To better characterize quasi-UFP (PM0.25, dp < 0.25 μm), we conducted a year-long sampling campaign at 10 distinct areas in the megacity of Los Angeles, including source, near-freeway, semi-rural receptor and desert-like locations. Average PM0.25 mass concentration ranged from 5.9 to 16.1 μg m−3 across the basin and over different seasons. Wintertime levels were highest at the source site, while lowest at the desert-like site. Conversely, summertime concentrations peaked at the inland receptor locations. Chemical mass reconstruction revealed that quasi-UFP in the basin consisted of 49–64% organic matter, 3–6.4% elemental carbon, 9–15% secondary ions (SI), 0.7–1.3% trace ions, and 5.7–17% crustal material and trace elements, on a yearly average basis. Organic carbon (OC), a major constituent of PM0.25, exhibited greatest concentrations in fall and winter at all sites, with the exception of the inland areas. Atmospheric stability conditions and particle formation favored by condensation of low-volatility organics contributed to these levels. Inland, OC concentrations peaked in summer due to increased PM0.25 advection from upwind sources coupled with secondary organic aerosol formation. Among SI, nitrate peaked at semi-rural Riverside sites, located downwind of strong ammonia sources. Moreover, ionic balance indicated an overall neutral quasi-UFP aerosol, with somewhat lower degree of neutralization at near-freeway sites in winter. Anthropogenic metals peaked at the urban sites in winter while generally increased at the receptor areas in summer. Lastly, coefficients of divergence analysis showed that while PM0.25 mass is relatively spatially homogeneous in the basin, some of its components, mainly EC, nitrate and several toxic metals, are unevenly distributed. These results suggest that population exposure to quasi-UFP can substantially vary by season and over short spatial scales in the megacity of Los Angeles.

Chemical characterization and source apportionment of indoor and outdoor fine particulate matter (PM2.5) in retirement communities of the Los Angeles Basin

Concurrent indoor and outdoor measurements of fine particulate matter (PM2.5) were conducted at three retirement homes in the Los Angeles Basin during two separate phases (cold and warm) between 2005 and 2006. Indoor-to-outdoor relationships of PM2.5 chemical constituents were determined and sources of indoor and outdoor PM2.5 were evaluated using a molecular marker-based chemical mass balance (MM-CMB) model. Indoor levels of elemental carbon (EC) along with metals and trace elements were found to be significantly affected by outdoor sources. EC, in particular, displayed very high indoor-to-outdoor (I/O) mass ratios accompanied by strong I/O correlations, illustrating the significant impact of outdoor sources on indoor levels of EC. Similarly, indoor levels of polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes were strongly correlated with their outdoor components and displayed I/O ratios close to unity. On the other hand, concentrations of n-alkanes and organic acids inside the retirement communities were dominated by indoor sources (e.g. food cooking and consumer products), as indicated by their I/O ratios, which exceeded unity. Source apportionment results revealed that vehicular emissions were the major contributor to both indoor and outdoor PM2.5, accounting for 39 and 46% of total mass, respectively. Moreover, the contribution of vehicular sources to indoor levels was generally comparable to its corresponding outdoor estimate. Other water-insoluble organic matter (other WIOM), which accounts for emissions from uncharacterized primary biogenic sources, displayed a wider range of contributions, varying from 2 to 73% of PM2.5, across all sites and phases of the study. Lastly, higher indoor than outdoor contribution of other water-soluble organic matter (other WSOM) was evident at some of the sites, suggesting the production of secondary aerosols as well as direct emissions from primary sources (including cleaning or other consumer products) at the indoor environments.

Source apportionment of the redox activity of urban quasi-ultrafine particles (PM0.49) in Thessaloniki following the increased biomass burning due to the economic crisis in Greece.

Abstract The source apportionment of the redox activity of quasi-ultrafine particles (PM0.49), measured by the cell-free dithiothreitol (DTT) assay, was attempted at two urban sites (urban traffic, UT and urban background, UB) in Thessaloniki, northern Greece, following the increased biomass burning due to the economic crisis. Both, the per-mass and per-volume DTT redox activities of PM0.49 particles were found to be substantially higher at the UB site in the cold season underscoring the increase in PM toxicity with the shift from traditional oil burning to biomass burning for residential heating. Two different approaches were employed to link the measured redox activity of PM0.49 with specific sources: (a) Principal Component Analysis of the chemical components of PM0.49 followed by Multilinear Regression of the measured redox activity on factor tracers (PCA-MLR), and (b) Robotic Chemical Mass Balance receptor modeling of the ambient PM0.49 mass followed by Multilinear Regression of the redox activity on the estimable source contributions (RCMB-MLR). Both approaches indicated that the major contributors to the measured redox activity of PM0.49 were vehicular traffic at the urban traffic site and residential wood burning at the urban background site.

Diurnal and seasonal trends in the apparent density of ambient fine and coarse particles in Los Angeles

Diurnal and seasonal variations in the apparent density of ambient fine and coarse particulate matter (PM2.5 and CPM [PM2.5-10], respectively) were investigated in a location near downtown Los Angeles. The apparent densities, determined by particle mass-to-volume ratios, showed strong diurnal and seasonal variations, with higher values during the warm phase (June to August 2013) compared to cold phase (November 2012 to February 2013). PM2.5 apparent density showed minima during the morning and afternoon rush hours of the cold phase (1.20g cm(-3)), mainly due to the increased contribution of traffic-emitted soot particles, and highest values were found during the midday in the warm phase (2.38g cm(-3)). The lowest CPM apparent density was observed during the morning rush hours of the cold phase (1.41g cm(-3)), while highest in early afternoon during the warm phase (2.91g cm(-3)), most likely due to the increased wind-induced resuspension of road dust.

Associations of oxidative stress and inflammatory biomarkers with chemically-characterized air pollutant exposures in an elderly cohort

BACKGROUND Exposure to air pollution has been associated with cardiorespiratory morbidity and mortality. However, the chemical constituents and pollution sources underlying these associations remain unclear. METHOD We conducted a cohort panel study involving 97 elderly subjects living in the Los Angeles metropolitan area. Airway and circulating biomarkers of oxidative stress and inflammation were measured weekly over 12 weeks and included, exhaled breath condensate malondialdehyde (EBC MDA), fractional exhaled nitric oxide (FeNO), plasma oxidized low-density lipoprotein (oxLDL), and plasma interleukin-6 (IL-6). Exposures included 7-day personal nitrogen oxides (NOx), daily criteria-pollutant data, five-day average particulate matter (PM) measured in three size-fractions and characterized by chemical components including transition metals, and in vitro PM oxidative potential (dithiothreitol and macrophage reactive oxygen species). Associations between biomarkers and pollutants were assessed using linear mixed effects regression models. RESULTS We found significant positive associations of airway oxidative stress and inflammation with traffic-related air pollutants, ultrafine particles and transition metals. Positive but nonsignificant associations were observed with PM oxidative potential. The strongest associations were observed among PM variables in the ultrafine range (PM <0.18µm). It was estimated that an interquartile increase in 5-day average ultrafine polycyclic aromatic hydrocarbons was associated with a 6.3% (95% CI: 1.1%, 11.6%) increase in EBC MDA and 6.7% (95% CI: 3.4%, 10.2%) increase in FeNO. In addition, positive but nonsignificant associations were observed between oxLDL and traffic-related pollutants, ultrafine particles and transition metals while plasma IL-6 was positively associated with 1-day average traffic-related pollutants. CONCLUSION Our results suggest that exposure to pollutants with high oxidative potential (traffic-related pollutants, ultrafine particles, and transition metals) may lead to increased airway oxidative stress and inflammation in elderly adults. This observation was less clear with circulating biomarkers.

Environmental pollution and emission factors of electronic cigarettes, heat-not-burn tobacco products, and conventional cigarettes

ABSTRACT The increasing popularity of electronic cigarettes (e-cigarettes) and, more recently, the new “heat-not-burn” tobacco products (iQOS) as alternatives to traditional tobacco cigarettes has necessitated further documentation of and research into the composition and potential health risks/benefits of these devices. In a recent study, we compared second-hand exposure to particulate metals and organic compounds from e-cigarettes and traditional cigarettes, by conducting continuous and time-integrated measurements in an indoor environment, followed by computing the emission rates of these species using a single-compartment mass balance model. In this study, we have used a similar approach to further expand our previous analyses by characterizing black carbon, metal particles, organic compounds, and size-segregated particle mass and number concentrations emitted from these devices in addition to the newly marketed iQOS. Analysis of the iQOS side-stream smoke indicated that the particulate emission of organic matter from these devices is significantly different depending on the organic compound. While polycyclic aromatic hydrocarbons (PAHs) were mostly non-detectable in the iQOS smoke, certain n-alkanes, organic acids (such as suberic acid, azelaic acid, and n-alkanoic acids with carbon numbers between 10 and 19) as well as levoglucosan were still emitted in substantial levels from iQOS (up to 2–6 mg/h during a regular smoking regimen). Metal emissions were reduced in iQOS smoke compared to both electronic cigarettes and conventional cigarettes and were mostly similar to the background levels. Another important finding is the presence of carcinogenic aldehyde compounds, including formaldehyde, acetaldehyde, and acrolein, in iQOS smoke, although the levels were substantially lower compared to conventional cigarettes. Copyright

Associations of Source-Specific Fine Particulate Matter With Emergency Department Visits in California.

While many studies have investigated the health effects associated with acute exposure to fine particulate matter (particulate matter with an aerodynamic diameter less than or equal to 2.5 μm (PM2.5)), very few have considered the risks of specific sources of PM2.5 We used city-specific source apportionment in 8 major metropolitan areas in California from 2005-2009 to examine the associations of source-specific PM2.5 exposures from vehicular emissions, biomass burning, soil, and secondary nitrate and sulfate sources with emergency department visits (EDVs) for cardiovascular and respiratory diseases, including 7 subclasses. Using a case-crossover analysis, we observed associations of vehicular emissions with all cardiovascular EDVs (excess risk = 1.6%, 95% confidence interval: 0.9, 2.4 for an interquartile-range increment of 2.8 µg/m(3)) and with several subclasses of disease. In addition, vehicular emissions, biomass burning, and soil sources were associated with all respiratory EDVs and with EDVs for asthma. The soil source, which includes resuspended road dust, generated the highest risk estimate for asthma (excess risk = 4.5%, 95% confidence interval: 1.1, 8.0). Overall, our results provide additional evidence of the public health consequences of exposure to specific sources of PM2.5 and indicate that some sources of PM2.5 may pose higher risks than the overall PM2.5 mass.

Source apportionment of fine particulate matter and risk of term low birth weight in California: Exploring modification by region and maternal characteristics

Previous studies have demonstrated associations between fine particulate matter (PM2.5) and risk of term low birth weight (TLBW; birth weight<2500g and gestational weeks≥37weeks). However, it remains unclear which PM2.5 sources mainly contribute to these associations, and which subgroups (e.g. by residential region and maternal characteristics) may be more susceptible to these exposures. Using California birth records and PM2.5 data from eight monitoring sites from 2002 to 2009, we examined the relationship between exposures to total PM2.5 and PM2.5 sources and risk of TLBW. Source apportionment was performed for each site using Positive Matrix Factorization, and five PM2.5 sources (i.e., secondary ammonium sulfate, secondary ammonium nitrate, vehicular emissions, biomass burning, and resuspended soil) were included in our analysis. Mean gestational and trimester exposures were calculated for mothers with ZIP codes located within a 20km radius of monitors (N=1,050,330). Logistic regression was conducted and adjusted for maternal age, race/ethnicity, and education, as well as gestational age, year of birth, apparent temperature exposure during gestation, and neighborhood level percentage of households below poverty level. Increased risks of TLBW associated with each interquartile range increase in exposure were 4.9% (95% confidence interval: 2.6, 7.3) for total PM2.5, 7.7% (4.7, 10.7) for secondary ammonium sulfate, 5.6% (3.5, 7.7) for resuspended soil, and 3.1% (1.3, 4.9) for secondary ammonium nitrate. Differences in associations were found between inland and coastal regions, and between northern and southern regions for several sources. Results also showed effect measure modification by maternal race/ethnicity and education, with the lowest risk of TLBW associated with PM2.5 exposures found in mothers with at least a college education and Asian mothers. Some PM2.5 sources may be more harmful than others, and a better understanding of the relative toxicity of PM2.5 from each source could lead to more targeted and cost-effective regulations to protect public health.

Spatio-temporal trends and source apportionment of fossil fuel and biomass burning black carbon (BC) in the Los Angeles Basin

In this study, we evaluated the spatial and temporal trends of black carbon (BC) in the Los Angeles Basin between 2012-2013 and 2016-2017. BC concentrations were measured in seven wavelengths using Aethalometers (AE33) at four sites, including central Los Angeles (CELA), Anaheim, Fontana, and Riverside. Sources of BC were quantified using the equivalent black carbon (EBC) model. Results indicate that total BC concentrations nearly doubled in colder period compared to the warm period. Source apportionment results revealed that fossil fuel combustion has higher annual contributions (ranging from 82% in Riverside to 91% in CELA) than biomass burning (ranging from 9.3% in CELA to 18.7% in Riverside) to the total BC concentrations at all sites. This trend was more clearly observed at the sites closer to major freeways, such as CELA and Anaheim. The relative contribution of fossil fuel to total BC concentrations was higher in the warm period, whereas biomass burning had higher contributions in the colder period. The diurnal variation of fossil-fuel-originated BC (BCff) to the total BC concentrations revealed major rises during the traffic rush hours, especially in the warm period. In contrast, the fraction of BC originating from biomass burning (BCbb) peaked at nighttime, particularly in the cold period, reaching values as high as 25-30% of total BC concentration. Moreover, we observed a clear decrease in both absolute BC concentrations as well as relative contributions of BCff to total BC concentrations from 2012-2013 to 2016-2017, which can be attributed to the implementation of strict regulations in California to reduce transportation-related PM emissions. Results from the present study suggest that as these regulations become increasingly stricter, the relative contributions of traffic sources to BC also decrease, thereby making the impact of non-fossil fuel combustion sources, such as biomass burning, to the overall BC levels more significant.