A STUDY ON THE ACUTE EFFECTS OF AMBIENT AIR PARTICLES ON PULMONARY FUNCTION OF CHINESE SCHOOLCHILDREN

Abstract

ISEE-49 Introduction: As information about the health risks associated with air pollution has become available, attention has focused increasingly on smaller air particles such as particulate matter with an aerodynamic diameter to or less than a 10 or 2.5u (PM10 or PM2.5, respectively). A number of recent studies conducted in Asia, Europe and the United States have shown that acute exposure to current levels of air particles is associated with adverse health status, including mortality, hospital admissions due to asthma, severity of preexisting chronic illness, low birth weight and pulmonary functions. Our objective was to evaluate the acute effects of ambient air particles on pulmonary function. Methods: This study was directed at the schoolchildren (3rd and 6th grades) living in a Beijing, China. Each child was provided with a mini-Wright peak flow meter and a preformatted health symptom diary for 40 days, and was trained on their proper use. Participants were instructed to perform the peak flow test three times in the standing position, three times daily (9 am, 12 pm, and 8 pm), and to record all the readings along with the symptoms (cold, cough, and asthmatic symptoms) experienced that day. Daily measurement of ambient air particles (PM10 and PM2.5) was obtained in the corner of the playground of the participating elementary school for the same period of this longitudinal study. The relationship between daily PEFR and ambient air particle levels was analyzed using a mixed linear regression models including gender, height, the presence of respiratory symptoms, and daily average temperature and relative humidity as an extraneous variable. Results: The total number of subjects participating in this longitudinal study was 87. The range of daily measured PEFR in this study was 253 to 501 L/min. In general, a PEFR measured in the morning was lower than a PEFR measured in the evening (or afternoon) on the same day. The daily mean concentrations of PM10 and PM2.5 over the study period were 180.2 ug/m3 and 103.2 ug/m3, respectively. The IQR (inter-quartile range) of PM10 and PM2.5 were 91.8 ug/m3 and 58.0 ug/m3. During the study period, the national ambient air quality standard of 150 ug/m3 was exceeded in 23 days (57.5%), which shows that the pollutant status of PM10 is very serious in the study area. The analysis showed that an increase of 1 ug/m3 of PM10 corresponded to 0.59 ug/m3 increment of PM2.5. Daily mean PEFR was regressed with the 24-hour average PM10 (or PM2.5) levels, weather information such as air temperature and relative humidity, and individual characteristics including gender, height, and respiratory symptoms. The analysis showed that the increase of air particle concentrations was negatively associated with the variability in PEFR. We estimated that the IQR increment of PM10 or PM2.5 (at the time lag 1 day) were associated with 1.54 L/min (95% Confidence intervals −2.14, −0.94) and 1.56 L/min (95% CI −2.16, −0.95) decline in PEFR. Conclusions: Our objective was to evaluate the relationship between ambient air particles and lung function measured by peak expiratory flow rate (PEFR) among school children. We conducted a community-based diary study and used a classic design for the respiratory effects of ambient air particles and used longitudinal information for 40 days of follow-up starting from March 25, 2003 to May 3, 2003. The relationship between daily PEFR and ambient air particle levels was analyzed using a mixed linear regression models including gender, height, the presence of respiratory symptoms, and daily average air temperature and relative humidity as an extraneous variable. In conclusion, we found a significant association between outdoor levels of particulate matter and PEFR, and estimated that the IQR increment of PM10 or PM2.5 (91.8 ug/m3, 58.0 ug/m3, respectively) were significantly associated with 1.54 L/min and 1.56 L/min decline in PEFR.