[Impact of Particulate Matter (PM 2,5 ) and children's hospitalizations for respiratory diseases. A case cross-over study].

Introduction: With seven million inhabitants, Santiago de Chile reaches high levels of air pollution in winter, the particulate matter usually exceeds WHO standards.

Objective: To assess the influence of air pollution caused by particulate matter on children's hospitalizations due to respiratory diseases between 2001 and 2005 in the Metropolitan Region of Chile, independently from the environmental presence of respiratory syncytial virus (RSV).

Material And Method: 72,479 public and private hospitalizations due to respiratory diseases of children under 15 years of age residing in the study region were analyzed using a time-stratified alternating case-control design. The main evaluations were: hospitalizations due to respiratory diseases (J00-J99), pneumonia (J12-J18); asthma (J21.0 - J21.9), and bronchiolitis (J45 - J46). Daily compilation of temperature data, PM10, PM2.5, ozone, respiratory virus (RSV), and environmental humidity.

Results: Mean values of PM10 and PM2,5 were 81.5 and 41.2 pg/m3 respec tively. The average temperature was 12.8 °C and air humidity 72.6%. An increase of 10 pg/m3 of PM25 with one and two days of lag was associated with an hospitalizations increase due to respiratory diseases close to 2%, this percentage increased to 5% when the exposure was with eight days of lag, reflecting synergism between particulate matter and respiratory viruses (RSV).

Conclusion: Short air pollution exposure can lead to children's hospitalizations due to respiratory diseases.