Short-term effects of ambient air pollution exposure on respiratory hospitalizations among children in the State of Mexico.

Exposure to air pollutants is a global concern that threatens pediatric respiratory health. Children are particularly susceptible to respiratory diseases because of their developing respiratory and immune systems. This study aimed to evaluate the association between short-term exposure to ambient air pollutants and hospitalization for respiratory diseases among children in the Metropolitan Zone of the Toluca Valley, Mexico. Daily concentrations of PM₂.₅, PM₁₀, CO, NO₂, and O₃ were collected from fixed atmospheric monitoring stations, and hospital admission records were obtained from a regional general hospital of the Instituto Mexicano del Seguro Social. Children younger than 5 years of age hospitalized for respiratory diseases between January and December 2023 were included. Associations were estimated using adjusted conditional logistic regression within a matched case-crossover design. The primary exposure window was Lag 1-7. Models were adjusted for mean ambient temperature and relative humidity, and sensitivity analyses evaluated alternative cumulative exposure windows and single-day lags. A total of 266 children were hospitalized with respiratory diseases. PM₂.₅ exposure was associated with an increased risk of hospitalization for viral pneumonia, bacterial pneumonia, and asthma, whereas CO exposure was associated with bronchiolitis. Municipality-specific analyses suggested heterogeneous associations across the study area, with several pollutant-related associations observed in San Mateo Atenco, Metepec, and Calimaya. These findings suggest that short-term exposure to ambient air pollution, particularly PM₂.₅, may contribute to respiratory morbidity among young children. Further studies are needed to confirm these findings and better characterize the role of air pollution in pediatric respiratory health.