REACH-OUT: Race, Ethnicity, and Air Pollution in COVID-19 Hospitalization OUTcomes

Determining whether chronic exposure to air pollution contributes to observed disparities in COVID-19 outcomes requires integrating multiple determinants of patient vulnerability to COVID-19, given the complex interactions that contribute to health disparities. Exposure to adverse social and structural factors heightens vulnerability to environmental exposures, potentially resulting in increased risk of unfavorable COVID-19 outcomes. Additionally, as populations are often exposed to various co-occurring adverse factors in the setting of disinvested neighborhoods and communities, examining such factors individually may not be sufficient to fully understand how they may modify the effects of air pollutant exposures. In an effort to explain COVID-19-related disparities observed in New York City (NYC³), this study aimed to estimate the effect of chronic air pollutant exposures on the risk of COVID-19 morbidity and mortality and to determine whether these effects vary by neighborhood-level vulnerability as defined by social and structural factors.

We used harmonized electronic health record (EHR) data from five healthcare systems in NYC to derive a study population of hospitalized or emergency department (ED) patients diagnosed with COVID-19 from March 1, 2020, through February 28, 2021, who had a NYC zip code of residence. To reduce potential selection bias, we also constructed a subset of the study population restricted to patients with residential zip codes in the typical catchment area of the hospitals affiliated with the EHR data repository. We estimated air pollutant concentrations for fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), black carbon (BC), and ozone (O₃) by using zip code-level 11-year averages based on data from the 2009-2019 New York City Community Air Survey. For each pollutant, we constructed Cox proportional hazards models to estimate the hazards of fatality (i.e., dying from COVID among individuals with COVID) and hospital length of stay. Additionally, for each pollutant, we constructed Poisson regression models to estimate RRs (RRs) for acute respiratory distress syndrome (ARDS), pneumonia, mechanical ventilation, and dialysis during hospitalization and risk of hospitalization among ED patients. Models were adjusted for age, sex, body mass index, smoking status, history of chronic disease, and a neighborhood environmental vulnerability index (NEVI). Interaction terms were used to evaluate effect modification between pollutant exposures and the NEVI metric. Additionally, we conducted supplementary analyses to determine the joint effects of air pollution and pre-existing chronic diseases and whether those relationships varied by NEVI tertile. To supplement the fatality analysis, we conducted an excess mortality analysis among the full urban population using all-cause mortality data from public health records for 2015-2020. Sensitivity analyses were performed to evaluate the effect of selection bias.

Exposures to NO₂, PM_2.5, and BC were positively associated with risks of ARDS, pneumonia, and dialysis, whereas O₃ exposure was inversely associated with these morbidity outcomes, likely because of the strong inverse correlation between O₃ and NO₂. Conversely, we observed an unexpected inverse association between exposures to NO₂, PM_2.5, and BC and risks of fatality and mechanical ventilation. We observed statistically significant effect modification by NEVI for some of the associations between NO₂, PM_2.5, O₃, and BC exposures and risks of ARDS, pneumonia, and dialysis. In areas with greater environmental vulnerability (i.e., higher NEVI metrics), there were generally stronger positive associations between air pollutant exposures and the risk of hospitalization among ED patients and risks of ARDS, pneumonia, and dialysis among hospitalized patients. Exposures to NO₂, PM_2.5, and BC were generally negatively associated with the risk of fatality, even in areas with higher NEVI metrics. Most positive associations between air pollution and COVID-19 outcomes were limited to the initial phase of the pandemic, except for the risk of hospitalization, which was positively associated with NO₂, PM_2.5, and BC exposures throughout the study period. Even after accounting for the NEVI metric and pre-existing chronic disease, racial disparities persisted in the effect of air pollution on risks of pneumonia and hospitalization, with the largest RRs among Black and Hispanic populations. Results of the all-cause mortality analysis also showed no evidence of greater excess mortality in areas with higher levels of air pollution. The greatest excess mortality was observed in areas with high NEVI metrics, regardless of air pollutant exposures.

When limiting to individuals in the hospital's typical catchment areas, the observed positive associations between air pollutant exposures and COVID-19-related morbidities such as ARDS, pneumonia, and use of dialysis were strongest in areas with higher neighborhood-level environmental vulnerability. Inverse associations between air pollutant exposures and severe outcomes like death and use of mechanical ventilation were unexpected findings that highlighted challenges in examining such associations at the population level in NYC.