PEDIATRICS Vol. 114 No. 2 August 2004, pp. 536-537
RELATIONSHIP OF OUTDOOR AIR QUALITY TO PEDIATRIC ASTHMA EXACERBATION
Helen Skolnick, MD
Princeton, NJ
Lierl MB, Hornung RW. Ann Allergy Asthma Immunol. 2003;90:28–33
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Purpose of the Study.
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To determine the relationship of outdoor air quality parameters
to asthma exacerbations among children.
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Study Population.
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Pediatric patients who had experienced an emergency department
visit or an inpatient hospitalization at Cincinnati Children’s
Hospital for treatment of acute asthma were studied.
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Methods.
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The number of emergency department visits and hospitalizations
for treatment of asthma were determined by review of emergency
department logs and a hospital computer database. Air quality
data were obtained from a centrally located monitoring station.
Ozone concentrations were continuously monitored, and data were
recorded as daily averages and the highest 1-hour average concentration
for each day. Concentrations of airborne particulates <10
µm in diameter were obtained by using a volumetric air
sampler with a size-selective inlet, and 24-hour average values
were calculated. Pollen and fungal counts were obtained by using
a Rotorod sampler (Multidata, Inc, Plymouth Meeting, PA). Multiple-regression
models were developed to examine all potential exposure measures
as predictors of the number of daily asthma visits. Poisson
regression analysis was used to model the daily number of asthma
visits as a function of air quality data and temporal variables.
In the data analyses, air quality measures from 0 to 5 days
before the asthma visit date were used, to account for delayed
effects.
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Results.
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A series of Poisson regression models was used to identify predictors
of changes in the number of asthma visits. Initially, the logarithm
of pollen counts and the month of the year (April to October)
were significant predictors of the number of asthma visits.
The number of asthma visits per day was associated with pollen
counts reported for the same day (
P = .014). The effect was
increasingly strong, however, for pollen counts recorded 1,
2, and 3 days before the visit. The logarithm of the pollen
counts lagged 3 days was the most significant predictor of asthma
visits (
P < .001). This effect was very strong during the
summer and spring months; however, in the autumn, when pollen
counts and asthma visits were both high, daily variations in
pollen counts did not account for the variations in daily asthma
visits as they did during other seasons. The analyses also showed
a synergistic effect between pollen and particulate levels,
in that the exposure-response to pollen counts was moderately
high on days when particulate matter levels were low but was
significantly higher on days when particulate matter levels
were >33 µg/m
3. Fungal spore counts and average ozone
concentrations were not significant predictors of asthma visits.
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Conclusions.
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Ambient concentrations of pollens and small particles were strongly
associated with emergency visits for treatment of pediatric
asthma in Cincinnati, Ohio. Concentrations of ozone did not
appear to be associated with pediatric asthma exacerbations.
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Reviewer’s Comments.
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Several studies have demonstrated associations between particulate
matter levels and emergency department visits, and several have
shown correlations between pollen counts and asthma symptoms.
This study shows the added effects of both on asthma symptoms.
It would be interesting to evaluate particulate matter levels
and pollen counts in various urban, suburban, and rural settings,
to assess their influence. In addition, examination of particulate
matter levels inside and outside households, schools, and offices
might give us a better understanding of the conditions that
influence asthma. The fact that pollen counts influenced asthma
admissions in the spring and summer but not the autumn might
be secondary to other factors that dominate during that season
(eg, cold weather and respiratory infections).
PEDIATRICS (ISSN 1098-4275). ©2004 by the American Academy of Pediatrics
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Purpose of the Study.
Study Population.
