Effect of hourly concentration of particulate matter on peak expiratory flow in hospitalized children: A panel study

Abstract

Background: Little information is available on the possible association between hourly short-term air pollution and peak expiratory flow (PEF) in asthmatic children. Methods. PEF was measured twice daily, from October through December, 2000, in 17 children aged 8 to 15 years hospitalized with severe asthma. A total of 1198 PEF measurements were made at 7 a.m. and 1175 at 7 p.m. Measurements were conducted immediately prior to medication under the guidance of trained nurses. PEF changes were estimated in 10-g/m3 increments of particulate matter with a 50% cut-off aerodynamic diameter of 2.5 m (PM 2.5), with adjustment for sex, age, height, and temperature. Lagged-hour exposures of up to 24 hours were examined. Results: Increased 24-hour mean concentration of PM2.5 was associated with a decrease in both morning and evening PEF (-3.0 l/minute; 95%CI: -4.6, -1.4 and -4.4 l/minute; 95%CI: -7.1, -1.7, respectively). In addition, hourly concentrations of PM2.5 and PEF showed a significant association between some lags of PM2.5 and PEF. Effect size was almost -3 l/minute in both morning and evening PEF for an hourly PM2.5 concentration of 10 g/m 3 in several lags. Even after adjustment for other air pollutants, some of the significant associations with PEF remained. Conclusion: Among hospitalized children with severe asthma, increased hourly concentration of PM2.5 was associated with a decrease in PEF. © 2011 Yamazaki et al; licensee BioMed Central Ltd.