RESUMEN
Aim: To measure the impact of day care attendance on lower respiratory tract infections in children under 2 years old in 2 urban settings with different degrees of air pollution. Subjects and Methods: a 26 week follow up, during fall and winter of 1991 and 1992, was performed to 98 children (48 attending day care and 50 controls) comming from Santiago, a city affected by severe air pollution and 95 children (46 Attending day care and 49 controls) coming from San felipe and Los Andes (villages with low air pollution). The incidence of lower respiratory infections was recorded by trained personnel and expressed as rates per 100 weeks of follow up. Day care settings in San Felipe and Los Andes were state funded whereas those from Santiago were private. All premises has wooden or plastic floors and smoking was forbidden. During the follow up years, no respiratory epidemic were recorded. Results: The socioeconomic level of children from San Felipe and Los Angeles was better. Children from Santiago were more exposed to tobacco smoke. The highest incidence of lower respiratory infections was found in children attending day care in San Felipe and Los Andes (31.2 episodes/100 weeks of observation), closely followed by control and day care attending children from Santiago (28.7 respectively) and control children from San felipe and Los Andes (18.2). Conclusions: Day care attendance in areas with low air pollution increases the risk of lower respiratory infections. Instead, in highly polluted areas, the infection rates do not increase