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The association of seasonal variations of asthma hospitalization with air pollution among children in Taiwan.

BACKGROUND
The impact of air pollution on asthma in children in different age group has not been well defined.


OBJECTIVE
This study aimed to evaluate the association between seasonal variations in air pollution and asthma hospitalization of children within a two-year period.


METHODS
Using the National Health Insurance database, seasonal variations in hospitalization trends in children with a primary diagnosis of asthma (International Classification of Disease 9th revision, code 493) for patients aged < 18 years from 2001 to 2002 were investigated. Data on the average concentration of nitrogen dioxide (NO(2)), carbon monoxide (CO), ozone(O(3)), sulphur dioxide (SO(2)), and particles with aerodynamic diameter < 10 microm (PM(10)) for each month were obtained from the Environmental Protection Department through 71 stations of air quality monitor distributed nationwide. PSI value (pollutants standard index)> 100 was considered poor air quality. Seasonal variations in asthma admissions were compared to the air pollution quality data using Spearman's rank correlation.


RESULTS
Asthma hospitalization was not related to the number of days when the PSI was > 100 during the 24-months period (r = -0.361; p = 0.083). However, it was significantly associated with seasonal changes in the concentration of each pollutant. The most strongly related air pollutant variable was PM(10) (standardized coefficients 0.384), followed by 0(3) (standardized coefficients 0.255) and SO(2) (standardized coefficients 0.162) concentrations. The association of seasonal changes in asthma hospitalization with these pollutants was greater in pre-school and school age children. Temperature and rainfall in all seasons were not related to asthma hospitalization. None of the pollutants were associated with seasonal variations in admission rate for adolescents.


CONCLUSION
Seasonal variations of asthma hospitalization among preschool children are associated with concentration of air pollutants.