Ambient Air Pollution and COVID-19 in California.

introductionAs of December 2023, more than 6.9 million people globally had died from COVID-19, including more than 1.165 million deaths in the United States. It is estimated that approximately 18.8 million people in the United States have experienced post-acute COVID-19 conditions, also known as post-acute sequelae of SARS-CoV-2 (PASC) or long COVID, in the first 3 years after the pandemic. Although some initial cases of long COVID have resolved, with the ongoing incidence of COVID-19, roughly 17.8 million persons in the United States continue to suffer from long COVID at the time of this writing.

methodsIn this study, we investigated relationships between ambient air pollution and COVID-19-related outcomes, including incidence, severity, mortality, and long COVID conditions. We used advanced models to estimate exposures, incorporating numerous air pollutants, particle species, and wildfire emissions. We used administrative COVID-19 data and several cohorts of patients from a large health system, and each was formed to evaluate different hypotheses. Daily air pollution exposures for Southern California were estimated with high spatial and chemical resolution, using a combination of land use regression and chemical transport models for the years 2016, 2019, and 2020. Exposure variables included ozone (O • COVID-19 cases (N = 773,374) and deaths (N = 14,311), by age, race, and sex, for 308 ZIP codes in Los Angeles County between June 19 and January 3, 2021. A negative binomial regression was performed for both individual and multiple ambient air pollutants to evaluate their associations with COVID-19 incidence and mortality. • Patients with COVID-19 who were admitted to Kaiser Permanente Southern California (KPSC) hospitals between June 1, 2020, and January 30, 2021 (N = 21,415). Cox proportional hazards models were used to evaluate associations between ambient air pollutant exposure and COVID-19 mortality. A subset was of KPSC patients with COVID-19 who received care exclusively in KPSC hospitals (N = 15,978). A multistate survival model was used to examine how air pollution affects the transition to recovery or deterioration to more severe COVID-19 states (e.g., intensive care admission or death). A subset was of KPSC patients with COVID-19 who maintained membership with KPSC for 1 year after hospital discharge (N = 12,634). We combined a set of 45 diagnoses of post-acute sequelae of SARS-CoV-2 (PASC) into categories based on organ systems and then studied a subset of these PASC categories that could be affected by air pollution, including cardiac, cardiometabolic, pulmonary, and neurological conditions. Logistic regression was used to evaluate associations between 30-day air pollution exposure before hospital admission and PASC conditions diagnosed at 3 months and 12 months post-discharge.

resultsPM

conclusionsBroadly, we concluded that several common air pollutants are associated with COVID-19 incidence, mortality, and progression to more severe states of illness, including long COVID conditions. Air pollution is a modifiable environmental risk factor that could be altered to improve the prognosis of COVID-19, thereby also reducing the public health impacts of coronaviruses now and in the future. This is particularly important for preventing long COVID, as evidence suggests that PASC conditions can occur even in vaccinated individuals. Given that 10% to 30% of individuals with COVID-19 will experience some form of PASC, which can have lifelong debilitating effects,