Effects of traffic air pollution and hornbeam pollen on adult asthma hospitalizations in Zagreb.

BACKGROUND

Environmental factors play an important role in asthma morbidity, although the contribution of individual pollutants or pollens in exacerbating asthma is not completely elucidated. Despite the evidence of importance of the hornbeam pollen in inducing allergic sensitization, its role in provoking asthma exacerbation has not been evaluated. The aim of the present study was to investigate effects of traffic pollutants on adult asthma hospitalization adjusting for pollens including hornbeam.

METHODS

During a 3-year period, health and environmental data were collected and analyzed. Daily asthma hospitalizations were regressed on pollutants and potential confounding variables using an autoregressive Poisson model.

RESULTS

The risk of asthma hospitalization was associated significantly with the 95th to 99th percentile increase in levels of nitrogen dioxide (RR = 1.22; 95% CI: 1.05-1.40), carbon monoxide (RR = 1.25; 95% CI: 1.01-1.55) and hornbeam pollen (RR = 1.21; 95% CI: 1.11-1.30). The effect of nitrogen dioxide was delayed by 5 days. No statistically significant increase in the risk of asthma hospitalization was found for PM(10) particles. A comparison among the standardized regression coefficients and their respective p values indicates that the most important risk factor for asthma hospitalization is associated with hornbeam pollen levels. No statistically significant interactions between pollutants and pollens were detected.

CONCLUSIONS

The current results suggest that traffic-related air pollution is associated with increased risk of adult asthma hospitalization. Nonetheless, the most significant risk for asthma hospitalization is associated with hornbeam pollen levels in the city of Zagreb.