Ambient Air Pollution and Chronic Obstructive Pulmonary Disease: The Multiethnic Cohort Study

Rationale: Globally, chronic obstructive pulmonary disease (COPD) was the third leading cause of death in 2019. Although tobacco smoking is the predominant risk factor, the role of long-term air pollution exposure in increasing the risk of COPD remains unclear. Moreover, few studies that account for smoking history and other known risk factors have been conducted in racially and ethnically minoritized and socioeconomically diverse populations. Objectives: We sought to evaluate the association of ambient air pollution with COPD in a multiethnic population in California. Methods: In the Multiethnic Cohort Study of 38,654 African-American, Japanese-American, Latino, and White California participants who were enrolled in the fee-for-service component of Medicare, we used Cox proportional hazards regression to estimate the association of time-varying ambient air pollutants-particulate matter with an aerodynamic diameter ⩽2.5 μm or ⩽10 μm, nitrogen dioxide, carbon monoxide, ozone, benzene, and ultrafine particles (UFPs)-with COPD risk (n = 10,915 cases; 8.8 yr of follow up). Subgroup analyses were conducted by race and ethnicity, sex, smoking status as recorded on the Multiethnic Cohort Study baseline questionnaire, and neighborhood socioeconomic status. Results: We observed a positive association of nitrogen oxide (per 50 ppb) with risk of COPD (hazard ratio = 1.45; 95% confidence interval = 1.35-1.55). The associations of nitrogen dioxide (per 20 ppb), particulate matter with an aerodynamic diameter ⩽2.5 μm (10 μg/m³) or ⩽10 μm (10 μg/m³), carbon monoxide (1,000 ppb), and UFPs (interquartile range = 5,241.7 particles/cm³) with risk of COPD were in similar directions, as these air pollutants are highly correlated with nitrogen oxide. These associations were found in African-American, Latino, and Japanese-American participants, but not in Whites (P heterogeneity across race and ethnicity <0.04). These associations also differed by neighborhood socioeconomic status, with effects being stronger in racially and ethnically minoritized populations and residents of low-SES neighborhoods. Conclusions: Long-term ambient air pollutant exposure is associated with COPD risk in a multiethnic, older adult (age >65 yr) population.