Respiratory Health Effects of Airborne Particulate Matter: The Role of Particle Size, Composition, and Oxidative Potential—The RAPTES Project

Background: Specific characteristics of particulate matter (PM) responsible for associations with respiratory health observed in epidemiological studies are not well established. High correlations among, and differential measurement errors of, individual components contribute to this uncertainty. Objectives: We investigated which characteristics of PM have the most consistent associations with acute changes in respiratory function in healthy volunteers. Methods: We used a semiexperimental design to accurately assess exposure. We increased exposure contrast and reduced correlations among PM characteristics by exposing volunteers at five different locations: an underground train station, two traffic sites, a farm, and an urban background site. Each of the 31 participants was exposed for 5 hr while exercising intermittently, three to seven times at different locations during March–October 2009. We measured PM10, PM2.5, particle number concentrations (PNC), absorbance, elemental/organic carbon, trace metals, secondary inorganic components, endotoxin content, gaseous pollutants, and PM oxidative potential. Lung function [FEV1 (forced expiratory volume in 1 sec), FVC (forced vital capacity), FEF25–75 (forced expiratory flow at 25–75% of vital capacity), and PEF (peak expiratory flow)] and fractional exhaled nitric oxide (FENO) were measured before and at three time points after exposure. Data were analyzed with mixed linear regression. Results: An interquartile increase in PNC (33,000 particles/cm3) was associated with an 11% [95% confidence interval (CI): 5, 17%] and 12% (95% CI: 6, 17%) FENO increase over baseline immediately and at 2 hr postexposure, respectively. A 7% (95% CI: 0.5, 14%) increase persisted until the following morning. These associations were robust and insensitive to adjustment for other pollutants. Similarly consistent associations were seen between FVC and FEV1 with PNC, NO2 (nitrogen dioxide), and NOx (nitrogen oxides). Conclusions: Changes in PNC, NO2, and NOx were associated with evidence of acute airway inflammation (i.e., FENO) and impaired lung function. PM mass concentration and PM10 oxidative potential were not predictive of the observed acute responses.


Table S1
Geometric means and minimum-maximum of 5-hour average air pollution concentrations Page 5

Exposure measurements
We determined gravimetrically concentrations of PM 10 and PM 2.5 , and measured the absorbance of those samples using a smoke stain reflectometer. We calculated PM 2.5-10 mass concentrations as the differences between PM 10 and PM 2.5 . Endotoxin content of PM 10 samples was measured using an LAL assay. PNC was measured using a condensation particle counter. With a high volume sampler we collected PM 2.5-10 and PM 2.5 samples in which we measured the concentrations of EC and OC, trace metals, e.g., iron (Fe), copper (Cu), nickel (Ni), vanadium (V) (both water-soluble and "total" acid-extracted fractions), as well as

Single-pollutant models of associations between air pollution and FE NO
PNC was positively associated with participants' FE NO immediately after exposure, two hours after exposure, and the next morning (RAPTES 2012;

Single-pollutant models of associations between air pollution and lung function
NO 2 and NO X were associated with decrease in FVC at all time points. PNC was associated with drops in FVC immediately after exposure and the next morning, while watersoluble Ni -immediately after and two hours after the exposure (RAPTES 2012; Table R2).
Nitrogen oxides were also associated with drops in FEV 1 two hours after and the morning after the exposure (RAPTES 2012; Table R3). PNC, absorbance, EC (F) and water-soluble Ni were associated with drops in FEV 1 at single time points. We also observed positive associations of FEV 1 with OC (F) (immediately after exposure) and sulfate (two hours after and the morning after exposure). In the outdoor datasets, nitrogen oxides were associated with  29.4 (12.8-42.6) 9.6 (8.1-11.2) 9.1 (7.0-11.8) Absorbance  Absorbance is expressed in 10 -5 /m; endotoxin is presented in EU/m 3 ; PM 10 , PM 2.5 , EC, OC, NO 3 -, SO 4 2are expressed in µg/m 3 ; PNC in 10 3 /cm 3 ; Fe, Cu, Ni and V in ng/m 3 ; OP in 1/m 3 ; O 3 , NO 2 and NO X in ppb. "Tot" denotes total, while "sol" water-soluble metal extraction. "C" is the coarse and "F" is the fine PM fraction.
6/8  "Tot" denotes total, while "sol" water-soluble metal extraction. "C" is the coarse and "F" is the fine PM fraction.
Fields in light shading indicate Spearman's R above 0.7. In each row effect estimates for the indicated pollutant in two-pollutant models are presented. The effect estimates in a single-pollutant model are presented on the diagonal (dark shading). All models were adjusted for temperature, relative humidity, season, pollen counts, respiratory infection and adjustment pollutant (indicated in the header of each column). Estimates are percentage increases above population-average baseline expressed per outdoor-sites IQR. N=170, except all models including OP where N=153 and all models including EC (C), OC (C) and trace metals where N=166. "Tot" denotes total, while "sol" water-soluble metal extraction. "C" is the coarse and "F" is the fine PM fraction.

Precision in % coefficient of variation (CV).
Ranges in % > LOD for trace metals denote PM 2.5-10 and PM 2.5 fractions.