Fine particulate matter constituents and blood pressure in patients with chronic obstructive pulmonary disease: A panel study in Shanghai, China

Objective: The evidence is limited about the potentially different health effects of various chemical constituents of fine particulate matter (PM2.5). We thus assessed the acute effects of various chemical constituents of PM2.5 on blood pressure (BP). Methods: We performed a longitudinal panel study with six repeated visits in 28 urban residents with chronic obstructive pulmonary disease in Shanghai, China from May to July, 2014. Twelve (43%) of them took anti hypertensive medications. We measured resting BP by using a mercury sphygmomanometer and monitored real-time concentrations of PM2.5 constituents at a nearby site. Based on the linear mixed-effects model, we evaluated the effects of 10 major constituents in PM2.5 on BP, using a single-constituent model and a constituent-residual model after accounting for the multicollinearity. Results: We obtained a total of 168 pairs of effective BP measurements during the study period. There are moderate or high correlations among various PM2.5 constituents. An interquartile range increase of PM2.5 (19.1 mu g/m(3)) was associated with increments of 1.90 mmHg [95% confidence interval (CI): 0.66, 3.13] in systolic BP, 0.68 mmHg (95%CI: -0.02, 1.37) in diastolic BP and 1.23 mmHg (95%CI: 0.19, 2.29) in pulse pressure. Some constituents of PM2.5, including organic carbon, elemental carbon, nitrate and ammonium, were robustly associated with elevated BP after controlling for total PM2.5 mass and accounting for multi-collinearity. Two constituents (magnesium and calcium) were associated with decreased BP. Conclusions: Organic carbon, elemental carbon, nitrate and ammonium may be mainly responsible for elevated BP from a short-term exposure to PM2.5.