The effects of long-term ambient air pollutant mixture exposure on incident diabetes: A prospective cohort study in China.

Background: Although an increasing number of studies have shown air pollution exposure is associated with diabetes, the potential causal effects of air pollutants on incident diabetes and the joint effects of air pollutant mixtures remain unclear.

Methods: We conducted a prospective cohort study that included 25,801 adults based on Chronic Disease of the Community Natural Population in the Beijing-Tianjin-Hebei region. Three-year mean concentrations of air pollutants (PM_2.5, PM₁₀, PM₁, and NO₂) and PM_2.5 components (ammonium [NH₄⁺], nitrate [NO₃^-], sulfate [SO₄^2-], and chloride ion [Cl^-]) were obtained from China High Air Pollutants database. Targeted maximum likelihood estimation was used to estimate potential causal relationships between long-term air pollution exposure and diabetes incidence. The joint effects of air pollutant mixtures on diabetes and the contribution of each pollutant were assessed using Quantile G-computation.

Results: In single-pollutant models, moderate and high concentrations of PM_2.5, PM₁₀, PM₁, NO₂, NH₄⁺, NO₃^-, SO₄^2-, and Cl^- exposure were significantly associated with diabetes risk compared with low concentrations of air pollutants. In multi-pollutant models, the joint effect of air pollutant mixture (PM_2.5, PM₁₀, PM₁, and NO₂) on diabetes was 1.006 (1.004, 1.009). After replacing PM_2.5 with PM_2.5 components in the mixture, the effect estimates remained robust at 1.015 (1.008, 1.021), and the positive effect was driven primarily by NH₄⁺ at 43.66 %, followed by NO₃^- at 39.20 %.

Conclusions: Our results revealed relationships between long-term air pollutant exposure and incident diabetes. Furthermore, NH₄⁺ and NO₃^- might be strong contributors. These findings support targeted air quality interventions to reduce diabetes risk.