The acute effects of particulate matter air pollution on ambulatory blood pressure: A multicenter analysis at the hourly level

Epidemiological evidence from ambulatory blood pressure monitoring is needed to clarify the associations of particulate air pollution with blood pressure and potential lag patterns. We examined the associations of fine and coarse particulate matter (PM_2.5, PM_2.5-10) with ambulatory blood pressure among 7108 non-hypertensive participants from 7 Chinese cities between April 2016 and November 2020. Hourly concentrations of PM_2.5 and PM_2.5-10 were obtained from the nearest monitoring stations. We measured four blood pressure indicators, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and pulse pressure (PP). Linear mixed-effect models combined with distributed lag models were applied to analyze the data. Generally, very short-term exposure to PM_2.5 was significantly associated with elevated blood pressure. These effects occurred on the same hour of blood pressure measurement, attenuated gradually, and became insignificant approximately at lag 12 h. An interquartile range (IQR, 33 μg/m³) increase of PM_2.5 was significantly associated with cumulative increments of 0.58 mmHg for SBP, 0.31 mmHg for DBP, 0.38 mmHg for MAP, and 0.33 mmHg for PP over lag 0 to 12 h. The exposure-response relationship curves were almost linear without thresholds, but tended to be flat at very high concentrations. No significant associations were observed for PM_2.5-10. Our study provides independent and robust associations between transient PM_2.5 exposure and elevated blood pressure within the first 12 h, and reinforces the evidence for a linear and non-threshold exposure-response relationship, which may have implications for blood pressure management and hypertension prevention in susceptible population.