Ambient particles during Asian dust events are usually sized less than 10 µm, known to be associated with the adverse effects on the general populations. But, there has been no considerable evidence linking these particles to the adverse effects on airways. The objectives of this study was to investigate the possible adverse effects of Asian dust events on respiratory function and symptoms in subjects with bronchial asthma.

From march to June 2002, Asthmatic patients who were diagnosed with bronchial challenge test or bronchodilator response were enrolled. We divided them into three groups; mild, moderate, and severe, according to the severity. Subjects with other organ insufficiency such as heart, kidney, liver, and malignancy were excluded. All patients completed twice daily diaries and recorded peak flow rate, respiratory symptom, and daily activity. Daily and hourly mean pollutant levels of particulate matter <10 µm in diameter(PM₁₀), nitrogen dioxide(NO₂), sulphur dioxide(SO₂), ozone(O₃) and carbon monoxide(CO) were measured at the 10 different monitoring sites.

Dust events occured 14 times during the study period. Daily averages of 4 air pollutant were measured with an increased level of PM₁₀, decreased level of NO₂ and SO₂, and no change in CO during dust days compared to those during control days. An increase in PM₁₀ concentration was associated with an increase of subjects with PEF variability of >20% (p<0.05), night time symptom(p<0.05), and a decrease in mean PEF (p<0.05), which were calculated by the longitudinal data analysis. Otherwise, there was no association between PM₁₀ level and bronchodialtor inhaler, and daytime respiratory symptoms.

This study shows evidence that ambient air pollution, especially PM₁₀, during Asian dust events, could be one of the many aggravating factors at least in patients with airway diseases. This data can be used as a primary source to set up a new policy on air environmental control and to evaluate the safety of air pollution index. We also expect that this research will help identify precise components of dust, which are more linked to the adverse effects.