The relationship of bronchitic symptoms to ambient particulate
matter and to particulate elemental and organic carbon (OC), nitrogen
dioxide (NO2), and other gaseous pollutants was examined in
a cohort of children with asthma in 12 Southern California communities.
Symptoms, assessed yearly by questionnaire from 1996 to
1999, were associated with the yearly variability of particulate matter
with aerodynamic diameter less than 2.5 m (odds ratio [OR]
1.09/g/m3
; 95% confidence interval [CI] 1.01–1.17), OC (OR 1.41/
g/m3
; 95% CI 1.12–1.78), NO2 (OR 1.07/ppb; 95% CI 1.02–1.13),
and ozone (OR 1.06/ppb; 95% CI 1.00–1.12). The ORs associated
with yearly within-community variability in air pollution were larger
than the effect of the between-community 4-year average concentrations.
In two pollutant models, the effects of yearly variation in
OC and NO2 were only modestly reduced by adjusting for other
pollutants, except in a model containing both OC and NO2; the
effects of all other pollutants were reduced after adjusting for OC
or NO2. We conclude that OC and NO2 deserve greater attention
as potential causes of the chronic symptoms of bronchitis in children
with asthma and that previous cross-sectional studies may have
underestimated the risks associated with air pollution.
The relationship of bronchitic symptoms to ambient particulatematter and to particulate elemental and organic carbon (OC), nitrogendioxide (NO2), and other gaseous pollutants was examined ina cohort of children with asthma in 12 Southern California communities.Symptoms, assessed yearly by questionnaire from 1996 to1999, were associated with the yearly variability of particulate matterwith aerodynamic diameter less than 2.5 m (odds ratio [OR]1.09/g/m3; 95% confidence interval [CI] 1.01–1.17), OC (OR 1.41/g/m3; 95% CI 1.12–1.78), NO2 (OR 1.07/ppb; 95% CI 1.02–1.13),and ozone (OR 1.06/ppb; 95% CI 1.00–1.12). The ORs associatedwith yearly within-community variability in air pollution were largerthan the effect of the between-community 4-year average concentrations.In two pollutant models, the effects of yearly variation inOC and NO2 were only modestly reduced by adjusting for otherpollutants, except in a model containing both OC and NO2; theeffects of all other pollutants were reduced after adjusting for OCor NO2. We conclude that OC and NO2 deserve greater attentionas potential causes of the chronic symptoms of bronchitis in childrenwith asthma and that previous cross-sectional studies may haveunderestimated the risks associated with air pollution.
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