Ultrafine particles in alveolar macrophages from normal children

Background-Increased ambient levels of particulate matter < 10 mum (PM10) from fossil fuel combustion are associated with an increased prevalence of respiratory symptoms in children. However, it is unknown whether, and to what extent, pollutant particles penetrate the paediatric lower airway. The capacity of alveolar macrophages (AM) to phagocytose inhaled material was used to directly assess exposure of normal children to particles. Methods-AM from 22 children aged 3 months to 16 years with no respiratory symptoms were obtained by nonbronchoscopic bronchoalveolar lavage prior to elective surgery. In each child the size and composition of environmental particles within single sections from 100 separate AM was determined by electron microscopy and microanalysis. Results-Single and clusters of particles were seen in AM from all children. The percentage of particle-containing AM ranged from 1% to 16% per child. Particles consisted of a carbonaceous core and all were ultrafine (<0.1 mum). Other elements such as metals and silicon were not detected. The percentage of particle-containing AM did not change with age, but was increased in children whose parents lived on a main road compared with those living on a quiet residential road (median 10% v 3%, p = 0.014). Conclusions-All children had AM containing ultrafine carbonaceous particles. The predominant source of these particles is most likely to be from the combustion of fossil fuels.