ACUTE EFFECTS OF AMBIENT INHALABLE PARTICLES IN ASTHMATIC AND NONASTHMATIC CHILDREN

Although increases in inhalable particle (PM10) concentrations have be en associated with acute reductions in the level of lung function and increased symptom reporting in children, including children with asthm a, it is not clear whether these effects occur largely in asthmatic ch ildren, or even whether asthmatic children are more likely to experien ce these effects than children without asthma. To address these points , the following subgroups of children were selected from a survey popu lation of all 2,200 elementary school children (6 to 13 yr of age) in a pulp mill community on the west coast of Vancouver Island: (1) all c hildren with physician-diagnosed asthma (n = 75 participated), (2) all children with an exercise-induced fall in FEV1 without diagnosed asth ma (n = 57), (3) all children with airway obstruction (FEV1/FVC < 0.76 ) without either of the above (n = 18), and (4) control children witho ut any of the above (n = 56). The children were followed for as long a s 18 mo with twice daily measurements of peak expiratory flow (PEF) an d daily symptom diary recording. Maximum daily PM10 concentration was 159 mu m/m(3) (median, 22.1), but only 8 d (1.2%) had concentrations a bove 100 mu g/m(3). In an analysis that accounted for time-varying cov ariates, and serially correlated and missing data, for the entire samp le of children, increases in PM10 were associated with reductions in P EF and increased reporting of cough, phlegm production, and sore throa t. For the subgroup of children with diagnosed asthma, PEF in the time period with the highest PM10 concentrations fell by an estimated 0.55 L/min (95% CI, 0.06 to 1.05) for a 10 mu g/m(3) PM10 increase above t he mean daily PM10 concentration of 27.3 mu g/m(3) and the odds of rep orted cough increased by 8% (95% CI, 0 to 16%); no consistent effects were observed in the other groups of children. It is concluded that ch ildren experience reductions in PEF and increased symptoms after incre ases in relatively low ambient PM10 concentrations, and that children with diagnosed asthma are more susceptible to these effects than are o ther children.