The association between chemical constituents of ambient fine particulate matter and obesity in adults: A large population-based cohort study

Objectives: Current evidence demonstrated that ambient fine particulate matter with an aerodynamic diameter ≤2.5 μm (PM_2.5) and its constituents may be obesogenic in children, but evidence from adults is lacking. Our aim was to characterize the association between PM_2.5 and its constituents and obesity in adults.

Methods: We included 68,914 participants from the China Multi-Ethnic Cohort (CMEC) baseline survey. Three-year average concentrations of PM_2.5 and its constituents were evaluated by linking pollutant estimates to the geocoded residential addresses. Obesity was defined as body mass index (BMI) ≥ 28 kg/m². Logistic regression was used to examine the relationship between PM_2.5 and its constituents and obesity. We performed weighed quantile sum (WQS) regression to get the overall effect of PM_2.5 and its constituents and the relative contribution of each constituent.

Results: Per-SD increase in PM_2.5 (odds ratio [OR] = 1.43, 95% confidence interval [CI]: 1.37-1.49), black carbon (BC) (1.42, 1.36-1.48), ammonium (1.43, 1.37-1.49), nitrate (1.44, 1.38-1.50), organic matter (OM) (1.45, 1.39-1.51), sulfate (1.42, 1.35-1.48), and soil particles (SOIL) (1.31, 1.27-1.36) were positively associated with obesity, and SS (0.60, 0.55-0.65) was negatively associated with obesity. The overall effect (OR = 1.34, 95% CI: 1.29-1.41) of the PM_2.5 and its constituents was positively associated with obesity, and ammonium made the most contribution to this relationship. Participants who were older, female, never smoked, lived in urban areas, had lower income or higher levels of physical activity were more significantly adversely affected by PM_2.5, BC, ammonium, nitrate, OM, sulfate and SOIL compared to other individuals.

Conclusion: Our study revealed that PM_2.5 constituents except SS were positively associated with obesity, and ammonium played the most important role. These findings provided new evidence for public health interventions, especially the precise prevention and control of obesity.