Respiratory tract pathology and cytokine imbalance in clinically healthy children chronically and sequentially exposed to air pollutants

Chronic exposure of children to a complex mixture of air pollutants leads t o recurrent episodes of upper and lower respiratory tract injury. An altere d nasal mucociliary apparatus leaves the distal acinar airways more vulnera ble to reactive gases and particulate matter. The heterogeneity of structur e in the human lung can impart significant variability in the distribution of ozone dose and particle deposition; this, in turn, influences the extent of epithelial injury and repair in chronically exposed children, Cytokines are low-molecular-weight proteins that act as intercellular mediators in i nflammatory reactions, including lung injury of various etiologies. Cytokin es are involved in generating inflammatory responses that contribute to inj ury at the lung epithelial and endothelial barriers. Mexico City is a 20-million-person megacity with severe air pollution probl ems. Southwest Metropolitan Mexico City (SWMMC) atmosphere is characterized by a complex mixture of air pollutants, including ozone, particulate matte r (PM), and aldehydes, There is radiological evidence that significant lowe r respiratory tract damage is taking place in clinically healthy children c hronically and sequentially exposed to air pollutants while growing up in S WMMC. We hypothesize that there is an imbalanced and dysregulated cytokine networ k in SWMMC children with overproduction of proinflammatory cytokines and cy tokines involved in lung tissue repair and fibrosis. The nature of the sust ained imbalance among the different cytokines ultimately determines the fin al lung histopathology, which would include subchronic inflammation, emphys ema, and fibrosis, Cytokines likely reach the systemic circulation and prod uce systemic effects, Individuals with an underlying respiratory or cardiov ascular disease are less able to maintain equilibrium of the precarious cyt okine networks, 2000 Harcourt Publishers Ltd.