Elevated Ambient PM10 Levels Affecting Respiratory Health of Schoolchildren in Chiang Mai, Thailand

Abstract

The health effects from exposure to particulate air pollution during the dry season (February-March) in northern Thailand, a longstanding problem, have become particularly acute since 2007. Although several studies have reported the effect of ambient PM 10 levels on airway oxidative stress and pulmonary function among respiratory disease patients, few studies have focused on healthy children, especially in Thailand. We conducted a prospective follow-up study to assess the respiratory health among schoolchildren exposed to different levels of ambient PM 10 by comparing exhaled malondialdehyde (MDA) concentrations and pulmonary function indices. Exhaled breath condensate (EBC) samples were obtained from individual participants. MDA in EBC has been proposed as a biomarker of airway oxidative stress. The participants were 54 healthy schoolchildren with median (min-max) age of 11 (10-12) years old from a pri- mary school in Chiang Mai City, Thailand. Questionnaires and EBC samples were collected twice, in the rainy season (July 2011, low PM 10 level) and the dry season (March 2012, high PM 10 level). It required about 10 minutes to collect EBC samples of 1-3 mL from individual participants, using an EBC-collect- ing apparatus that was modified specifically for this research from a standard hospital-use apparatus. MDA concentration in EBC was analyzed using HPLC- UV detection. Trained public health personnel performed the pulmonary function tests. The median of exhaled MDA concentrations in the rainy and dry seasons was 0.17 and 0.22 µM, respectively. Mean ± SD of forced expiratory volume in one-second/forced vital capacity ratios (FEV 1 /FVC) in the rainy and dry seasons was 94.6 ± 4.4 and 91.3 ± 4.7 percent predicted, respectively. Exhaled MDA concentration significantly increased and the FEV 1 /FVC ratio significantly decreased in the dry season (p<0.05). This results shows that elevated ambient