[Apply the Miettinen Formula to Assess the Health Benefits of the PM_2.5 Simulation Intervention on Metabolic...

Quantify the health benefits of various strategies for reducing PM_2.5 (aerodynamic diameter ≤ 2.5 μm) concentrations on the prevalence of metabolic syndrome (MetS) in the population, and provide more direct scientific evidence to support air pollution control efforts.

By integrating PM_2.5 exposure concentrations, population sizes of various cities in China, and relative risk data for PM_2.5-MetS from previous studies, the generalized impact fraction (GIF) for equivalent, fixed, threshold, and ratio interventions on PM_2.5 concentrations was estimated using the Miettinen formula. Specifically, the proportion of MetS cases that could be reduced by lowering the current exposure level to a specified level of interest was calculated.

Reducing PM_2.5 concentrations by 5, 10, 15, or 20 μg/m³ can lead to decreases in the number of MetS cases by 10.54% (95% CI: 10.52%-10.57%), 19.94% (95% CI: 19.90%-19.99%), 28.24% (95% CI: 28.16%-28.33%), and 35.41% (95% CI: 35.27%-35.55%), respectively. When the concentration is controlled to the minimum observed value (5.95 μg/m³) or does not exceed the WHO annual average standard (10 μg/m³), the proportions of MetS cases that can be avoided are 22.71% (95% CI: 18.77%-26.65%) and 17.24% (95% CI: 16.86%-17.62%), respectively. Using the ratio intervention method, reducing PM_2.5 concentrations by 30% and 50% can reduce the number of MetS cases by 7.41% (95% CI: 7.28%-7.53%) and 12.16% (95% CI: 11.96%-12.36%), respectively.

All four PM_2.5 intervention strategies can reduce the number of patients with MetS to varying degrees, with equivalent, minimum-value, and WHO threshold-based interventions demonstrating the greatest effects. Taking into comprehensive consideration, equivalent intervention is more efficient. In the future, efforts should be gradually focused on the correlation between actual environmental control measures and intervention strategies to directly guide the formulation of environmental protection policies.