Effects of long-term exposure to air pollutant mixture on blood pressure in typical areas of North China

Background

Studies about the combined effects of gaseous air pollutants and particulate matters are still rare.

Objectives

This study was performed based on baseline survey of the Diverse Life-Course Cohort in the Beijing-Tianjin-Hebei (BTH) Region of North China to evaluate the association of long-term air pollutants with blood pressure and the combined effect of the air pollutants mixture among 32821 natural han population aged 20 years or above.

Methods

Three-year average exposure to air pollutants (PM₁₀, PM_2.5, PM₁, O₃, SO₂, NO₂, and CO) and PM_2.5 components [black carbon (BC), ammonium (${\mathrm{NH}}_4^{+}$), nitrate (${\mathrm{NO}}_3^{-}$), sulfate (${\mathrm{SO}}_4^{2-}$), and organic matter (OM)] of residential areas were calculated based on well-validated models. Generalized linear mixed models (GLMMs) were used to estimate the associations of air pollutants exposure with the systolic blood pressure (SBP), diastolic blood pressure (DBP), Mean arterial pressure (MAP), pulse pressure (PP) and prevalent hypertension. Quantile g-Computation and Bayesian Kernel Machine Regression (BKMR) were employed to assess the combined effect of the air pollutant mixture.

Results

We found that long-term exposures of O₃, PM_2.5, and PM_2.5 components were stably and strongly associated with elevated SBP, DBP, and MAP and prevalent hypertension. O₃ increased SBP, DBP, and MAP at a similar extent, but with greater effects; while, PM_2.5 and PM_2.5 components had a greater impact on SBP than DBP, which increased PP simultaneously. In multi-pollutant models, the combined effects of the air pollutant mixture on blood pressure and prevalent hypertension was predominantly influenced by O₃, PM_2.5, and O₃, OM in different models, respectively. For example, O₃, PM_2.5 contributed 57.25 %, 39.22 % of the positive combined effect of the air pollutant mixture on SBP; and O₃, OM positively contributed 70.00 %, 30.00 % on prevalent hypertension, respectively. There were interactions between O₃, CO, SO₂ and PM_2.5 components on hbp, SBP and PP.

Conclusions

The results showed positive associations of air pollutant mixtures with blood pressure, where O₃ and PM_2.5 (especially OM) might be primary contributors. There were interactions between gaseous air pollutants and PM_2.5 components on blood pressure and prevalent hypertension.