In terms of volume concentration, ambient particles in both the accumulation mode and the coarse mode were significantly and positively associated with FeNO. In terms of surface area concentration, ambient particles only in the accumulation mode were significantly and positively associated with FeNO.
Moreover, UFP as a lump sum of both nucleation-mode and Aikten-mode particles did not show a significant association with FeNO. Results: In terms of number concentration, ambient particles in the Aitken mode and in the accumulation mode were significantly and positively associated with FeNO but particles in the nucleation mode were significantly and negatively associated with FeNO. We used linear mixed-effects models to assess the associations between various particle metrics and FeNO. Each participating child was measured for FeNO daily for 30 days. Particles were classified by size into the nucleation, Aitken, accumulation, or coarse mode, respectively, for calculating mode-specific number, surface area, active surface area, and volume concentrations. Methods: We conducted a panel study in 17 non-asthmatic children who attended schools and resided near a monitoring site at which particles in the size range of 3–800 nm were measured using a TDMPS and particles in the size range of 0.5 to 10 µm were measured using an APS. We examined a range of particle metrics (number, surface area, active surface area, and volume concentration) in relation to fractional exhaled nitric oxide (FeNO), a well-established biomarker of pulmonary inflammation. Background: There have been increasing concerns on potential health effects of ultrafine particles (UFP) but little is known as to what are the most biologically relevant metrics for these particles that make up very little mass concentration.
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