PM_2.5 constituents associated with childhood obesity and larger BMI growth trajectory: A 14-year longitudinal study

The association of specific PM_2.5 chemical constituents with childhood overweight or obesity (OWOB) remain unclear. Furthermore, the long-term impacts of PM_2.5 exposure on the trajectory of children's body mass index (BMI) have not been explored.

We conducted a longitudinal study among 1,450,830 Chinese children aged 6-19 years from Beijing and Zhongshan in China during 2005-2018 to examine the associations of PM_2.5 and its chemical constituents with incident OWOB risk. We extracted PM_2.5 mass and five main component exposure from Tracking Air Pollution in China (TAP) dataset. Cox proportional hazards models were applied to quantify exposure-response associations. We further performed principal component analysis (PCA) to handle the multi-collinearity and used quantile g-computation (QGC) approach to analyze the impacts of exposure mixtures. Additionally, we selected 125,863 children with at least 8 physical examination measurements and combined group-based trajectory models (GBTM) with multinomial logistic regression models to explore the impacts of exposure to PM_2.5 mass and five constituents on BMI and BMI Z-score trajectories during 6-19 years.

We observed each interquartile range increment in PM_2.5 exposure was significantly associated with a 5.1 % increase in the risk of incident OWOB (95 % confidence Interval [CI]: 1.036-1.066). We also found black carbon, sulfate, organic matter, often linked to fossil combustion, had comparable or larger estimates of the effect (HR = 1.139-1.153) than PM_2.5. Furthermore, Exposure to PM_2.5 mass, sulfate, nitrate, ammonium, organic matter and black carbon was significantly associated with an increased odds of being in a larger BMI trajectory and being assigned to persistent OWOB trajectory.

Our findings provide evidence that the constituents mainly from fossil fuel combustion may have a perceptible influence on increased OWOB risk associated with PM_2.5 exposure in China. Moreover, long-term exposure to PM_2.5 contributes to an increased odds of being in a lager BMI and a persistent OWOB trajectories.