Fine particles are more strongly associated than coarse particles with acute respiratory health effects in schoolchildren

Numerous studies have reported associations between airborne particles and a range of respiratory outcomes from symptoms to mortality. Current attenti on has been focused on the characteristics of these particles responsible f or the adverse health effects. We have reanalyzed three recent longitudinal diary studies to examine the relative contributions of fine and coarse par ticles on respiratory symptoms and peak expiratory flow in schoolchildren. In the Harvard Six Cities Diary Study, lower respiratory symptoms in a two- pollutant model were associated with an interquartile range increment in fi ne particles [(for 15 mu g/m(3) particulate matter (PM) <2.5 mu m in aerody namic diameter (PM2.5), odds ratio = 1.29, 95% confidence limits (CL) = 1.0 6, 1.57] but not coarse particles (for 8 mu g/m(3) PM2.5-10, odds ratio = 1 .05, 95% CL = 0.90, 1.23). In Uniontown, PA, we found that peak flow was as sociated with fine particles (for 15 mu g/m(3) PM2.1, peak flow = -0.91 lit ers/minute, 95% CL = -0.14, -1.68), especially fine sulfate particles, bur: not with coarse particles (for 15 mu g/m(3) PM2.1-10, +1.04 liters/minute, 95% CL = -1.32, +3.40). We found similar results for an equivalent childre n's cohort in State College, PA. We conclude that fine particles, especiall y fine sulfate particles, have much stronger acute respiratory effects than coarse particles.