A panel study on effects of ambient particles of different sizes and from different sources on blood pressure in healthy adults in an urban area of Beijing

Background Air pollution has become a leading risk factor for cardiovascular diseases. Increased blood pressure is one of the possible underlying pathways. However, the effects of source-specific pollution remain incompletely understood.

Objective This study aims to explore the associations of blood pressure in healthy adults with exposure to source-specific versus size-segregated ambient particles.

Methods Seventy-three healthy adults were recruited for a panel study and underwent four repeated measurements from November 2014 to January 2016. Blood pressure and serum levels of systemic inflammation markers hypersensitive C-reaction protein and homocysteine were measured at each visit. Particle number concentrations of particles in size fractions of 5.6-560nm and meteorological variables in the study area were collected. The sources were identified based on PNC_5.6-560 including a total of 32 size distribution segments, using the positive matrix factorization method. Linear mixed-effect models were constructed to estimate the effects of exposure to ambient particles on blood pressure in healthy adults after adjusting for selected confounders.

Results The five identified sources of ambient particles were gasoline vehicle emissions, aged vehicle emissions, nucleation, secondary aerosols, and others based on hourly PNC_5.6-560 during the study period. The participants' diastolic blood pressure was positively associated with the exposure to the particles from secondary aerosols and aged vehicle emissions at moving average 1 and 2 days prior to clinic visit (P < 0.05). Significant increases (mean and 95%CI) in diastolic blood pressure of 2.9 (1.3-4.4) and 2.1 (0.4-3.7) mmHg and 1.7 (0.1-3.4) and 2.9 (0.6-5.1) mmHg were associated with an interquartile range increase in the number concentrations of particles from secondary aerosols and aged vehicle emissions at moving average 1 and 2 days prior to clinic visit, respectively. Stronger associations were found between particles and increased blood pressure in participants with body mass index equal to or over 25 kg·m^-2 and higher levels of serum hypersensitive C-reaction protein and homocysteine.

Conclusion Acute exposure to particles from secondary aerosols and aged vehicle emissions may increase the diastolic blood pressure in healthy adults, and ambient particles have a stronger effect on adults with overweight and a higher level of systemic inflammation.