Number concentration and size of particles in urban air: Effects on spirometric lung function in adult asthmatic subjects

Daily variations in ambient particulate air pollution are associated with v ariations in respiratory lung Function. It has been suggested that the effe cts of particulate matter may be due to particles in the ultrafine (0.01-0. 1 mum) size range. Be-cause previous studies on ultrafine particles only us ed self-monitored peak expiratory now rate (PEFR), we assessed the associat ions between particle mars and number concentrations in several size ranges measured at a central site and measured (biweekly) spirometric lung functi on among a group of 54 adult asthmatics (n = 495 measurements). We also com pared results to daily morning, afternoon, and evening PEFR measurements do ne at home (n = 7,672-8,110 measurements), The median (maximum) 24 hr numbe r concentrations were 14,500/cm(3) (46,500/cm(3)) ultrafine particles and 8 00/cm(3) (2,800/cm3) accumulation mode (0.1-1 mum) particles. The median (m aximum) mass concentration of PM2.5 (particulate matter <2.5 <mu>m) and PM1 0 (particulate matter <10 <mu>m in aerodynamic diameter) were 8.4 mug/m(3) (38.3 mug/m(3)) and 13.5 mug/m(3) (73.7 mug/m(3)), respectively. The number of accumulation mode particles was consistently inversely associated with PEFR in spirometry. Inverse, but nonsignificant, associations were observed with ultrafine particles, and no associations were observed with large par ticles (PM10). Compared to the effect estimates for self-monitored PEFR, th e effect estimates for spirometric PEFR tended to be larger. The standard e rrors were also larger, probably due to the lower number of spirometric mea surements. The present results support the need to monitor the particle num ber and size distributions in urban air in addition to mass.