Effects of long-term exposure to fine particulate matter components on the incidence of type 2 diabetes

Objective To assess the effects of long-term exposure to five components of fine particulate matter (PM_2.5) on the incidence of type 2 diabetes.

Methods A total of 3 788 middle-aged and elderly adults were enrolled by the survey based on the data in China Health and Retirement Longitudinal Study (CHARLS) in 2011 and 2015. Bayesian kernel machine regression (BKMR) was performed to analyze the individual, interactive, and joint effects of black carbon, ammonium, nitrate, organic matter, and sulfate on fasting blood glucose, glycated hemoglobin and the incidence risks of type 2 diabetes. Posterior inclusion probability (PIP) was used to estimate the significance of each component, and the component with PIP more than 0.5 was considered a significant variable.

Results The result showed that black carbon had a significant effect on fasting blood glucose (PIP=0.75), and there were no significant variables associated with glycated hemoglobin or the incidence risk of type 2 diabetes. When the other components were at the 25th, 50th, and 75th percentiles (P₂₅, P₅₀, P₇₅), for every interquartile range (IQR) increase in the concentration of black carbon, fasting blood glucose was increased by 0.59 (95%CI: 0.13, 1.05), 0.61 (95%CI: 0.19, 1.03) and 0.57 (95%CI: 0.11, 1.03) mmol/L, respectively. There were no interactive effects among the five components. The joint effect analysis showed that compared with the concentrations fixed at P₅₀ for all components, the concentrations of all components at P₇₀ induced the greatest change in fasting blood glucose, which was increased by 0.12 (95%CI: 0.02, 0.21) mmol/L.

Conclusion This study suggests that long-term exposure to black carbon alone may increase fasting blood glucose in middle-aged and elderly Chinese people. It is necessary to strengthen the prevention and control of black carbon in PM_2.5, which provides a basis for further prevention of the incidence risk of type 2 diabetes.This study suggests that long-term exposure to PM_2.5 components is not associated with glycated hemoglobin and the incidence risk of type 2 diabetes, while long-term exposure to black carbon alone and joint exposure to PM_2.5 components can increase fasting blood glucose in middle-aged and elderly Chinese people. It is necessary to strengthen the prevention and control of black carbon in PM_2.5, which provides a basis for further prevention of the incidence of type 2 diabetes.