Association of long-term exposure to local industry- and traffic-specific particulate matter with arterial blood pressure and incident hypertension

Background: Long-term exposure to fine particulate matter (PM_2.5) may lead to increased blood pressure (BP). The role of industry- and traffic-specific PM_2.5 remains unclear. Objective: We investigated the associations of residential long-term source-specific PM_2.5 exposure with arterial BP and incident hypertension in the population-based Heinz Nixdorf Recall cohort study. Methods: We defined hypertension as systolic BP ≥ 140 mmHg, or diastolic BP ≥ 90 mmHg, or current use of BP lowering medication. Long-term concentrations of PM_2.5 from all local sources (PM_2.5ALL), local industry (PM_2.5IND) and traffic (PM_2.5TRA) were modeled with a dispersion and chemistry transport model (EURAD-CTM) with a 1 km² resolution. We performed a cross-sectional analysis with BP and prevalent hypertension at baseline, using linear and logistic regression, respectively, and a longitudinal analysis with incident hypertension at 5-year follow-up, using Poisson regression with robust variance estimation. We adjusted for age, sex, body mass index, lifestyle, education, and major road proximity. Change in BP (mmHg), odds ratio (OR) and relative risk (RR) for hypertension were calculated per 1 μg/m³ of exposure concentration. Results: PM_2.5ALL was highly correlated with PM_2.5IND (Spearman's ρ = 0.92) and moderately with PM_2.5TRA (ρ = 0.42). In adjusted cross-sectional analysis with 4539 participants, we found positive associations of PM_2.5ALL with systolic (0.42 [95%-CI: 0.03, 0.80]) and diastolic (0.25 [0.04, 0.46]) BP. Higher, but less precise estimates were found for PM_2.5IND (systolic: 0.55 [−0.05, 1.14]; diastolic: 0.35 [0.03, 0.67]) and PM_2.5TRA (systolic: 0.88 [−1.55, 3.31]; diastolic: 0.41 [−0.91, 1.73]). We found crude positive association of PM_2.5TRA with prevalence (OR 1.41 [1.10, 1.80]) and incidence of hypertension (RR 1.38 [1.03, 1.85]), attenuating after adjustment (OR 1.19 [0.90, 1.58] and RR 1.28 [0.94, 1.72]). We found no association of PM_2.5ALL and PM_2.5IND with hypertension. Conclusions: Long-term exposures to all-source and industry-specific PM_2.5 were positively related to BP. We could not separate the effects of industry-specific PM_2.5 from all-source PM_2.5. Estimates with traffic-specific PM_2.5 were generally higher but inconclusive.