Strak, M; Janssen, NA; Godri, KJ; Gosens, I; Mudway, IS; Cassee, FR; Lebret, E; Kelly, FJ; Harrison, RM; Brunekreef, B; Steenhof, M; Hoek, G
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. Investigate which PM characteristics have the most consistent associations with acute changes in respiratory function in healthy volunteers. Methods. We used a semi-experimental design to accurately assess exposure. We increased exposure contrast and reduced correlations among PM characteristics by exposing volunteers at 5 different locations- an underground train station, two traffic sites, a farm and an urban background site. Each of the 31 volunteers was exposed for 5 hours, while exercising intermittently, 3-7 times at different locations from 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 (OP). Lung function (FEV1, FVC, FEF25-75, PEF) 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% to 17%) and 12% (95% CI: 6% to 17%) FENO increase over baseline immediately and two hours post-exposure, respectively. A 7% (95% CI: 0.5% to 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 and NOX. Conclusions. Changes in PNC, NO2 and NOX were associated with evidence of acute airway inflammation (FENO) and impaired lung function. PM mass concentration and PM10 OP were not predictive of the observed acute responses.
