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

Shin Yamazaki,Masayuki Shima,Hiroko Watanabe,Michiko Ando,Toshiyuki Nishimuta,Hiroshi Nitta

doi:10.1186/1476-069x-10-15

Abstract

BackgroundLittle information is available on the possible association between hourly short-term air pollution and peak expiratory flow (PEF) in asthmatic children.MethodsPEF 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-μg/m3 increments of particulate matter with a 50% cut-off aerodynamic diameter of ≤2.5 μm (PM2.5), with adjustment for sex, age, height, and temperature. Lagged-hour exposures of up to 24 hours were examined.ResultsIncreased 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 μg/m3 in several lags. Even after adjustment for other air pollutants, some of the significant associations with PEF remained.ConclusionAmong hospitalized children with severe asthma, increased hourly concentration of PM2.5 was associated with a decrease in PEF.

Highlights

Little information is available on the possible association between hourly short-term air pollution and peak expiratory flow (PEF) in asthmatic children
We estimated the change in PEF by 10-μg/m3 increments in PM2.5 adjusted for hourly concentration of Ox, which was measured at the same time as PM2.5, and the variables described above (2-pollutant model), and adjusted for hourly concentrations of nitrogen dioxide (NO2) and Ox measured at the same time as PM2.5, as well as the variables above (3-pollutant model)
Association between hourly concentration of PM2.5 and PEF in the morning Figure 2A shows the association between hourly concentration of PM2.5 and PEF at 7 a.m. using the singlepollutant model

Summary

Introduction

Little information is available on the possible association between hourly short-term air pollution and peak expiratory flow (PEF) in asthmatic children. Environmental causes of asthma are usually related to climatic conditions that promote appreciable concentrations of atmospheric pollutants and antigens, and while any exposed individual in the general population may develop respiratory symptoms, the effect appears to more severe in those with pre-existing asthma or other respiratory diseases. Sensitivity to asthmatic children appear more sensitive to PM than non-asthmatic children, the effect of transiently high concentrations of PM on PEF in these children remains unclear. To identify possible associations between hourly short-term air pollution and PEF, we analyzed hourly air pollution and PEF data noted in the medical records of children hospitalized with asthma

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Discussion

Conclusion