Air pollution effects are the result of a complex competition between factors, which lead to an accumulation of pollutants, and others that instead determine their removal and dilution in the atmosphere. The extent and modalities of emission (point or diffuse sources, emission height), the persistence times of the pollutants and the degree of mixing of the air are some of the main factors that produce space-time variations in the composition of the air.
This is one of the problems most felt by the populations of the large urban agglomerations, which has only begun to worry since the seventies. Since that time, in fact, in some countries policies have been gradually implemented to reduce chemical agents and numerous other contaminants present in the air; these policies have produced the lowering of the concentrations of some pollutants such as sulfur dioxide, lead and carbon monoxide.
For others, for example nitrogen dioxide, ozone and atmospheric particulate, agents for which their criticality as regards health has been discovered more recently, have not brought the desired results. The effects on human health due to poor air quality mainly involve the respiratory system and the cardiovascular system.
The study: The acute effects of particulate matter air pollution on ambulatory blood pressure: A multicenter analysis at the hourly level, published on the Environment international, explained: "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 (PM2.5, PM2.5-10) with ambulatory blood pressure among 7108 non-hypertensive participants from 7 Chinese cities between April 2016 and November 2020. Hourly concentrations of PM2.5 and PM2.5-10 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 P M2.5 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 PM2.5 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 PM2.5-10. Our study provides independent and robust associations between transient PM2.5 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."