Aerosol Oxidative Potential in the Greater Los Angeles Area: Source Apportionment and Associations with Socioeconomic Position

Abstract

Oxidative potential (OP) has been proposed as a possible integrated metric for particles smaller than 2.5 μm in diameter (PM2.5) to evaluate adverse health outcomes associated with particulate air pollution exposure. Here, we investigate how OP depends on sources and chemical composition and how OP varies by land use type and neighborhood socioeconomic position in the Los Angeles area. We measured OH formation (OPOH), dithiothreitol loss (OPDTT), black carbon, and 52 metals and elements for 54 total PM2.5 samples collected in September 2019 and February 2020. The Positive Matrix Factorization source apportionment model identified four sources contributing to volume-normalized OPOH: vehicular exhaust, brake and tire wear, soil and road dust, and mixed secondary and marine. Exhaust emissions contributed 42% of OPOH, followed by 21% from brake and tire wear. Similar results were observed for the OPDTT source apportionment. Furthermore, by linking measured PM2.5 and OP with census tract level socioeconomic and health outcome data provided by CalEnviroScreen, we found that the most disadvantaged neighborhoods were exposed to both the most toxic particles and the highest particle concentrations. OPOH exhibited the largest inverse social gradients, followed by OPDTT and PM2.5 mass. Finally, OPOH was the metric most strongly correlated with adverse health outcome indicators.

Multiphase Kinetic Modeling of Air Pollutant Effects on Protein Modification and Nitrotyrosine Formation in Epithelial Lining Fluid

“…Recent studies suggest that the catalytic production of • OH radicals may be the main driver of the adverse health effects of PM 2.5 , rather than the chemical production of other oxidants such as H 2 O 2 . , This explanation is plausible given the high reactivity of • OH with the amino acids contained in proteins. Moreover, modified tyrosine residues in proteins, such as nitrotyrosine (Ntyr) and dityrosine (Dityr), are used as markers of oxidative stress. ,, Thus, in this study, we focus on the oxidation chemistry of tyrosine.…”

Nitroaromatic Compounds from Secondary Nitrate Formation and Biomass Burning Are Major Proinflammatory Components in Organic Aerosols in Guangzhou: A Bioassay Combining High-Resolution Mass Spectrometry Analysis

“…This may be determined by the difference in the ionization mechanism between the ESI sources . In comparison to ESI – , more reducing nitrogen organic compounds were detected in ESI + , which contains some highly toxic species, such as N-containing heterocyclic compounds and aromatic amides. , …”

“…Therefore, there is no distinction between the seasons, except for winter and summer, which may explain why there was no difference in the IL-8 distribution between spring and autumn (Mann–Whitney U test, P < 0.05) (Figure S2B). Compared to summer, winter conditions such as air stagnation, low vertical mixing height, and the increased distribution of semivolatile organic compounds to the particulate phase due to low temperature are all favorable factors for OAs accumulation . These factors resulted in the production of more toxic species during winter.…”

“…23 In comparison to ESI − , more reducing nitrogen organic compounds were detected in ESI + , which contains some highly toxic species, such as N-containing heterocyclic compounds and aromatic amides. 40,41 As shown in Figure 1, CHON molecules were the most abundant proinflammatory component, followed by CHO, and the remaining groups only accounted for a small proportion (Figure 1A-B, D-E). In ESI − /ESI + , 259 (intensity: 3.57% ± 1.90%) and 2432 (intensity: 14.29% ± 2.88%) proinflammatory molecules, respectively, belonged to the CHON group, and 117 (intensity: 2.34% ± 0.63%) and 671 (intensity: 4.07% ± 1.26%) molecules, respectively, belonged to the CHO group.…”

“…Compared to summer, winter conditions such as air stagnation, low vertical mixing height, and the increased distribution of semivolatile organic compounds to the particulate phase due to low temperature are all favorable factors for OAs accumulation. 40 These factors resulted in the production of more toxic species during winter. Based on our data, we propose that a specific composition in OAs and atmospheric evolution may play a dominant role in contributing to the IL-8 increase.…”