Objective To investigate the short-term effect of fine particulate matter (PM_2.5) and its different components including black carbon (BC), organic matter (OM), sulfate (SO₄^2-), nitrate (NO₃^-), and ammonium salt (NH₄⁺) on systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and pulse pressure (PP) in elderly hypertensive patients in Taiyuan city, China.

Methods According to specific inclusion and exclusion criteria, 352 hypertensive patients aged above 65 years were recruited from 6 communities in Taiyuan city in 2020, and a questionnaire survey was performed to collect the information on demographic features and lifestyle. The data on the concentrations of atmospheric PM_2.5 and its different components and meteorological data during the same period of time were matched based on the home address of the subjects, and the generalized linear model was used to investigate the association between air pollutants and blood pressure (BP), as well as the impact of the concentrations of exposure to PM_2.5 and its different components on BP in different subgroups.

Results Short-term exposure to atmospheric PM_2.5 was associated with the increases in SBP, DBP, and MAP in the elderly hypertensive patients (P < 0.05), with the maximum effective values on lag07, lag06, and lag06 d, respectively. Short-term exposure to SO₄^2- was associated with the increases in SBP, DBP, MAP, and PP in the elderly hypertensive patients (P < 0.05), with the maximum effective values on lag010, lag010, lag010, and lag9 d, respectively. The concentration of NO₃^- exposure on lag9 d was associated with the increases in SBP and PP in the elderly hypertensive patients (P < 0.05). Short-term exposure to NH₄⁺ was associated with the increases in SBP, MAP, and PP in the elderly hypertensive patients (P < 0.05), with the maximum effective values on lag010, lag010, and lag9 d, respectively. Stratified analysis showed significantly greater effects of PM_2.5 and its component NO₃^- on BP during the heating season and in the elderly male hypertensive patients, the elderly hypertensive patients with body mass index (BMI) ≥24 kg/m², and the elderly hypertensive patients who did not take antihypertensive drugs.

Conclusion The short-term exposure to PM_2.5 and its components SO₄^2-, NO₃^-, and NH₄⁺ can cause a significant increase in BP in elderly hypertensive patients. Elderly hypertensive patients during the heating season, elderly male hypertensive patients, elderly hypertensive patients with BMI ≥24 kg/m², and elderly hypertensive patients who do not take antihypertensive drugs are more susceptible to PM_2.5 and should take proper protection measures.