Air pollution and emergency department visits for disease of the digestive system

BACKGROUND AND AIM: The objective of this work was to investigate associations between air pollution and emergency department (ED) visits for diseases of the digestive system in Toronto, Canada. METHODS: The National Ambulatory Care Reporting System database was used to retrieve the cases of the diagnosed ED visits. The codes K00-K93 under Chapter XI: “Diseases of the digestive system” of the International Classification of Disease 10th Revision were applied to identify the corresponding ED visits. Only primary causes of ED visits were considered. The health data used in the study was organized as daily counts of ED visits, to which ambient air pollution and weather factors (temperature and relative humidity) were linked. Exposure to two air quality health indexes and six ambient air pollutants for exposure: fine particulate matter PM2.5, O3, CO, NO2, SO2, and maximum 8-hour average ozone was used. Statistical models were realized as conditional Poisson regressions. RESULTS:In total, 993,364 ED visits were analyzed as related to the digestive system. A total of 314 statistically significant (P-Value 0.05) positive correlations were obtained over the 14 day lag period (from 0 to 14 days). Majority of the positive associations occurred for lags from 0 to 4, and were in summary for all pollutants and strata 71, 46, 66, 25, and 35, respectively. For nitrogen dioxide, positive associations were noted with following relative risks (RR) for an increase of one interquartile range (IQR=8.8 ppb): RR= 1.032 (95% confidence interval: 1.025, 1.039), 1.013 (1.005, 1.020), 1.013 (1.006, 1.021), 1.008 (1.000, 1.015), and 1.008 (1.000, 1.015) for all patients and lags from 0 to 4 days, respectively. CONCLUSIONS:The results indicate that urban ambient air pollution could influence the daily cases of ED visits for diseases of the digestive system. Ambient nitrogen dioxide was identified as the main environmental factor contributing to these associations. KEYWORDS: Digestive, Nitrogen dioxide, Traffic-related, Short-term exposure