Ultrafine particles in urban air and respiratory health among adult asthmatics

Airborne particles are associated with adverse health effects and contribut e to excess mortality in epidemiological studies. A recent hypothesis propo ses that the high numbers of ultrafine (<0.1 pm diameter) particles in ambi ent air might provoke alveolar inflammation and subsequently cause exacerba tions in pre-existing cardiopulmonary diseases. To test the hypothesis adult asthmatics were followed with daily peak expir atory flow (PEF) measurements and symptom and medication diaries for sis mo nths, while simultaneously monitoring particulate pollution in ambient air. The associations between daily health endpoints of 57 asthmatics and indic ators of air pollution mere examined by multivariate regression models. Daily mean number concentration of particles, but not particle mass (PM10 ( particle mass < 10 pm), PM2.5-10, PM2.5, PM1), was negatively associated wi th daily PEF deviations. The strongest effects were seen for particles in t he ultrafine range. However, the effect of ultrafine particles could not de finitely be separated from other traffic generated pollutants, namely nitri c oxide, nitrogen dioxide and carbon monoxide. No associations were observe d with respiratory symptoms or medication use. Particle mass measurements can be strongly influenced by mechanically produ ced, soil-derived particles, which may not be associated with adverse healt h effects. Therefore, air quality monitoring should include particle number concentrations, which mainly reflect ultrafine particles.