Socioeconomic disparities in aerosol pollutant exposure may be amplified by ultrafine particles despite declining PM2.5

BACKGROUND AND AIM: No study has investigated the spatiotemporal race-ethnicity and income disparities in ultrafine particles (UFP; ≤0.1µm) exposure, which is increasingly identified as a key subcomponent of PM₂.₅-related health effects. This study aims to establish the importance of distinguishing UFP from PM₂.₅ and quantify their race-ethnicity and income disparities in New York State (NYS). METHODS: Exposure disparities among seven race-ethnicity groups (Hispanics of any race, non-Hispanic Asian, Black, Native, Pacific& White alone, and Other/Mixed) and by household income across spatial scales (state, county, county subdivision, NCHS urban levels) during the period 2013–2020 for UFP and PM₂.₅, were quantified using Census data. A global three-dimensional chemical transport model with state-of-the-science aerosol microphysical processes were used to estimate UFP/PM₂.₅ that have been validated extensively with observations. RESULTS: The average New Yorker was exposed to 5171#·cm⁻³ UFP and 8.2µg·m⁻³ PM₂.₅ in 2013–2020. Minority race-ethnicity groups were invariably exposed to greater daily aerosol pollution in NYS (+51–104% UFP & +1.9–32% PM₂.₅). Race-ethnicity exposure disparities for PM₂.₅ exposure have declined over time; by −6% from 2013–2017 and plateauing thereafter despite increasing PM₂.₅. Crucially and in contrast, these disparities have persisted (+10%) for UFP exposure and even widened in periods of declining UFP. Economic status (median household income) by itself does not reveal significant exposure disparities. However, in tandem with race-ethnicity it uncovers these disparities as disproportionately magnified for socioeconomically disadvantaged subgroups. CONCLUSIONS: PM₂.₅ decline was associated with decline in race-ethnicity exposure disparities. which continued despite a post-2018 reversal in PM₂.₅ trends. However, race-ethnicity UFP exposure disparities were much larger, more disproportionate, and increased or remained constant across various income strata and levels of urbanicity. The need to distinguish ultrafine (UFP) from fine (PM₂.₅) aerosols is established through microphysical, geostatistical, and exposure assessment perspectives. KEYWORDS: air pollution, ultrafine particles, particulate matter, environmental justice, socioeconomic status