Cumulative effect of PM2.5 chemical components surpasses PM2.5 mass on hypertension in older adults: A China-based national analysis

Abstract

The specific and cumulative effects of fine particulate matter (PM_2.5) components on hypertension remain less defined, notably in susceptible older adults. This national study utilized a representative sample of 220,425 older adults in China, to scrutinize their relationship. Residential PM_2.5 and five chemical components (black carbon (BC), organic matter (OM), sulphate (SO₄²⁻), nitrate (NO₃⁻), and ammonium (NH₄⁺)) were estimated by the bilinear interpolation. Associations between PM_2.5 and five chemical components with hypertension were examined through two-stage logistic regression models, with population attributable fractions (PAFs) determined via counterfactual analysis. Elevated exposure to PM_2.5 and its components was generally linked to higher hypertension prevalence. With each interquartile range increase, the odds ratio (OR) of hypertension rose by 1.09 (95 % CI: 1.08–1.11) for NO₃⁻, 1.06 (95 % CI: 1.05–1.08) for NH₄⁺, 1.06 (95 % CI: 1.05–1.07) for OM, 1.05 (95 % CI: 1.04–1.06) for BC, and 1.06 (95 % CI: 1.04–1.07) for SO₄^2-. Notably, the cumulative impact of five PM_2.5 chemical components (OR: 1.13, 95 % CI: 1.12–1.13) was significantly greater than the effect of total PM_2.5 mass alone (OR: 1.04, 95 % CI: 1.03–1.05). Regarding PAFs, NO₃⁻ represented the strongest contribution to hypertension, followed by OM, NH₄⁺, SO₄²⁻, and BC. Furthermore, the effects were accentuated in low socio-economic population. These findings underline that using total PM_2.5 as a surrogate marker may underestimate the comprehensive impact of its chemical components, underscoring the necessity for targeted interventions to reduce emissions of specific PM_2.5 chemical constituents.