Effects of short-term exposure to fine and ultrafine particles from indoor sources on arterial stiffness - A randomized sham-controlled exposure study.

Objectives: Particulate air pollution is linked to adverse cardiovascular effects, including arterial stiffness. The aim of the study was to investigate the effect of short-term exposure to indoor fine and ultrafine particles on augmentation index (AIx), augmentation pressure (AP), and pulse wave velocity (PWV), early signs of vascular damage.

Methods: We analyzed the association of particle emissions from typical indoor sources (candle burning - CB, toasting bread - TB, and frying sausages - FS) with changes in pulse wave analysis indices in 55 healthy adults in a randomized cross-over controlled exposure study. Particle mass concentration (PMC), size-specific particle number concentration (PNC) and lung-deposited particle surface area concentration (PSC) were measured during the 2 h exposure. AIx and AP were measured before, directly, 2, 4 and 24 h after exposure. PWV was measured directly and 24 h after exposure. We performed multiple mixed linear regression analyses of different particle metrics and AIx, AP and PWV.

Results: The highest mean PMC was observed during FS reaching a maximum of 210 μg/m PM. The maximal PNC for UFP <100 nm was reached during CB with 2.3 million particles/cm. PSC was similar across all three exposures (about 3000 μm/cm³). Strongest associations between different particles metrics and arterial stiffness indices could be observed for UFP from CB and FS and for PMC from TB. The highest mean increase could be observed for the UFP fraction <10 nm, measured during CB, and AIx with an increase of 9.5%-points (95%-CI: 3.1; 15.9). PSC seemed to follow the pattern of PNC. PM and PM from TB led to clear changes in AIx with biggest increases for PM of 5.8%-points (95%-CI: 3.2; 8.4) 2 h after exposure and for PM of 8.1%-points (95%-CI: 2.5; 13.7) directly after exposure.

Conclusions: Our study indicates effects of indoor exposure to fine and ultrafine particles on systemic arterial stiffness indices that depend on the indoor source as well as on particle metric. Differences in size-specific physical characteristics of source-specific particles might account for these differential effects. We did not observe clear and stable associations of indoor particle exposure and PWV.