Air quality and emergency pediatric care for symptoms of bronchial obstruction categorized by age bracket in Rio de Janeiro, Brazil.

Abstract

The objective of this study was to estimate the association between levels of air pollutants and respiratory symptoms in children. An ecological time-series study was conducted between April 2002 and March 2003 with daily data on PM10, SO2, CO, NO2, and O3 and paediatric care in emergency rooms due to symptoms indicating bronchial obstruction. The potential confounding factors considered were: time trend, seasonality, meteorological variables, respiratory infections and the effects of weekends and holidays. A semi-parametric Poisson regression was used to model the time series. Splines (data smoothing functions), indicator variables and cubic polynomials were used to adjust the effects of the confounding variables. A 5% significance level was adopted for the study. A statistically significant increase of 6.7% in paediatric visits of children of less than 2 years of age was associated with PM10. A 3% positive association with O3 showed borderline significance (p < 0.06) in this age bracket. Our findings highlight the existence of an acknowledged public health problem in Rio de Janeiro, Brazil, and also emphasize the need to identify the principal sources of air pollutants.

Full text

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Cad. Saúde Pública, Rio de Janeiro, 25(3):635-644, mar, 2009
635
Air quality and emergency pediatric care for
symptoms of bronchial obstruction categorized
by age bracket in Rio de Janeiro, Brazil
Qualidade do ar e atendimentos pediátricos de
emergência por sintomas de obstrução brônquica
categorizados por faixas etárias no Rio de Janeiro,
Brasil
1 Escola Nacional de Saúde
Pública Sergio Arouca,
Fundação Oswaldo Cruz,
Rio de Janeiro, Brasil.
2 Instituto de Medicina
Social, Universidade do
Estado do Rio de Janeiro,
Rio de Janeiro, Brasil.
Correspondence
M. Moura
Centro de Estudos da Saúde
do Trabalhador e Ecologia
Humana, Escola Nacional de
Saúde Pública Sergio Arouca,
Fundação Oswaldo Cruz.
Rua Leopoldo Bulhões 1480,
Rio de Janeiro, RJ
21041-210, Brasil.
moura@ensp.fiocruz.br
Marisa Moura 1
Washington Leite Junger 2
Gulnar Azevedo e Silva Mendonça 2
Antonio Ponce de Leon 2
Abstract
The objective of this study was to estimate the
association between levels of air pollutants and
respiratory symptoms in children. An ecological
time-series study was conducted between April
2002 and March 2003 with daily data on PM10,
SO2, CO, NO2, and O3 and paediatric care in
emergency rooms due to symptoms indicating
bronchial obstruction. The potential confound-
ing factors considered were: time trend, season-
ality, meteorological variables, respiratory infec-
tions and the effects of weekends and holidays. A
semi-parametric Poisson regression was used to
model the time series. Splines (data smoothing
functions), indicator variables and cubic polyno-
mials were used to adjust the effects of the con-
founding variables. A 5% significance level was
adopted for the study. A statistically significant
increase of 6.7% in paediatric visits of children
of less than 2 years of age was associated with
PM10. A 3% positive association with O3 showed
borderline significance (p < 0.06) in this age
bracket. Our findings highlight the existence of
an acknowledged public health problem in Rio
de Janeiro, Brazil, and also emphasize the need to
identify the principal sources of air pollutants.
Air Pollution; Asthma; Child
Introduction
Bronchial asthma is the most prevalent chronic
disease in childhood, and its prevalence is in-
creasing especially in large industrialized coun-
tries 1,2,3. Although the disease has a low case
fatality rate, it limits normal childhood activi-
ties in a large number of children. There are cur-
rently an estimated 300 million asthmatic in-
dividuals worldwide, a figure that will increase
by another 100 million by the year 2025, due in
part to the growing process of urbanization and
air pollution 4.
The contribution of air pollutants to the ap-
pearance of characteristic symptoms of bronchial
asthma has still not been fully elucidated. Some
evidence suggests that lesions in the airways and
pulmonary parenchyma, caused by exposure to
air pollutants, probably exacerbate the harmful
effects of viruses and/or allergens 5,6.
Distinct levels of maturation and the ana-
tomical development of the structures in the
immune and pulmonary systems from birth to
puberty determine the variations in responses
to environmental stimuli. In the first years of
life, the reduced size of the airways facilitates the
decrease in the bronchial lumen during the in-
flammatory processes accompanying viral infec-
tions. At this age, the respiratory syncytial virus
was found to be one of the most prevalent agents
involved 7,8. The respiratory manifestations are
indistinguishable from the characteristic clinical
ARTIGO ARTICLE

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Moura M et al.
636
Cad. Saúde Pública, Rio de Janeiro, 25(3):635-644, mar, 2009
picture of bronchial asthma, thus leading to con-
stant errors in aetiological diagnoses 9. From six
years of age onwards, the temporal association
with exposure to allergens, the recurrent evolu-
tion of acute clinical episodes, and the presence
of specific biological parameters characterizing
the immunological alterations of allergic diseas-
es characterize children with bronchial asthma.
Respiratory allergies and viral infections appear
to be independent and synergistic risk factors for
the development of symptoms of bronchial ob-
struction at this stage 8.
Rio de Janeiro is the second largest city in
Brazil, but the respiratory effects of air pollution
on the paediatric population have received little
investigation, while epidemiological data are
scarce concerning the prevalence of bronchial
asthma and other allergic diseases in the city’s
population 10.
The objective of this present study was to es-
timate the association between daily variations
in air pollutant levels and emergency room visits
due to obstructive airway diseases in the paedi-
atric population in a specific region of Rio de Ja-
neiro city, considering different age groups.
Material and methods
The epidemiological design of a time series eco-
logical study was adopted, with daily observation
of health events, air pollutant concentrations,
and meteorological factors.
All children from aged between one month
and 12 years who had come for emergency
medical treatment due to acute respiratory com-
plaints, at public health units with a high daily
volume of emergency medical care in the region
of Jacarepaguá, city of Rio de Janeiro, between 1st
April 2002 and 31 March 2003, were included in
the study.
The study area is located in the west side of
the city of Rio de Janeiro and covers 126.61km2,
with a paediatric population of 120,469 (Instituto
Pereira Passos. Armazém de dados. http://portal
geo.rio.rj.gov.br/serie_rfoco/municipio/index.
htm, accessed on 03/Oct/2005).
A team of previously trained professionals
conducted a daily selection of the patient treat-
ment forms that met the eligibility criteria. Af-
ter this stage, the presence of respiratory signs,
symptoms, or diagnoses was recorded on an
original instrument, with specific fields for fre-
quent causes of emergency paediatric visits such
as colds, otitis, eye irritation, cough, and asthma.
In addition, the reasons for the visits were clas-
sified as upper airways diseases, lower airways
diseases, and/or acute respiratory infections. It
was necessary to create this original instrument
because the medical records did not mention
the International Classification of Diseases (ICD)
or any other classification of the symptoms and
clinical diagnoses that would allow data stand-
ardization.
Due to the various forms of clinical manifes-
tations caused by the reduction in the bronchial
lumen and the absence of standardized annota-
tions, the field “asthma” was checked whenever
the medical records indicated bronchial asthma,
bronchiolitis, chest wheezing or wheezing, which
are frequently related to obstructive diseases
of the airways in children. This procedure was
necessary because the medical annotations fre-
quently referred merely to a sign or symptom,
without mentioning a probable diagnosis.
Hourly concentrations of particulate matter
with aerodynamic volume of up to 10 microns
(PM10), sulphur dioxide (SO2), nitrogen dioxide
(NO2), carbon monoxide (CO), and ozone (O3)
were recorded from an automatic monitoring
station located centrally in Jacarepaguá, and the
daily averages of these pollutants were used as
the indicators of the population’s exposure to air
pollution. The following criteria were used in or-
der to obtain the daily exposure for each pollut-
ant: for PM10, SO2, and NO2, at least 75% of the
hourly measures should be observed; for O3, the
maximum concentration during daylight time (6
am to 6 pm) was taken when at least 75% of the
measures were observed; and for CO, the maxi-
mum of an 8-hour running average if 75% of the
daily data were available.
During the study period, technical problems
caused several interruptions in the monitoring of
pollutants. By the end, there were records for 246
days of PM10, 201 days of NO2, 244 days of CO,
237 days of O3, and only 194 days of SO2. Given
the important gap in the environmental data on
SO2, the choice was made not to analyse the res-
piratory effects of this pollutant.
Flaws occurred in monitoring, both in short
sequences of days and long periods of several
consecutive days: 08-30 September 2002, 1st De-
cember 2002 to 15 January 2003, and 10 Febru-
ary 2003 to 16 March 2003. In order to minimize
possible spurious associations, information was
imputed from monitors located in other areas of
the city for gaps on single days or short periods.
The high correlation between the environmen-
tal pollutant levels measured in Jacarepaguá and
these other areas allowed the use of a data im-
putation procedure. The methodology adopted
in the imputation process was similar to that de-
scribed by Junger et al. 11, in which the estimates
are obtained by the spatial correlation between
the level of the same pollutant in the different

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AIR QUALITY AND EMERGENCY CARE IN CHILDREN WITH BRONCHIAL OBSTRUCTION
637
Cad. Saúde Pública, Rio de Janeiro, 25(3):635-644, mar, 2009
monitoring stations and the autocorrelation for
this pollutant level in the same monitoring sta-
tion over time.
The choice to replace only the gaps from
short intervals meant that the total observation
period for PM10 and CO was 262 out of 365 days.
The amount of data was smaller for NO2 and O3,
250 and 248 respectively, because the replace-
ment option only included one station.
Daily data on meteorological conditions: rel-
ative humidity and minimum, mean and maxi-
mum temperatures were measured in a station
located close to the study region. Information on
weather conditions from the current day, the two
previous days, and the mean for the two previous
days were used in the analysis. Rainfall was also
considered in the model due to the occasional
showers during the summer time, which often
cause floods in some areas of the city and, there-
fore, limits people’s access to health care units.
The outcome variable – emergency paedi-
atric visits due to obstructive bronchial symp-
toms – was stratified by age brackets: ≤ 2 years,
2-6 years, and 6-12 years. The exposure variables
were mean daily concentration of the air pollut-
ants PM10, NO2, CO, and O3. Time trend, season-
ality, weather conditions, anomalous days over
the course of the year, epidemics of respiratory
infections were the potential confounding vari-
ables regarded in the model. A Poisson regression
model was used, since the outcome variable con-
sisted of counts of events.
In the estimation of the effects of air pollut-
ants on health, the confounders showing daily
fluctuations needed to be accounted for. Gen-
eralized additive models (GAM) have been used
for this purpose, since they are quite flexible, al-
lowing for the inclusion oif parametric and non-
parametric structures in the same model. This
study used splines (data smoothing functions)
to adjust for the effects of time trends and long-
term seasonality as well as the effects of meteoro-
logical variables.
The days of the week that showed anomalous
behaviour, like weekends, holidays, days between
holidays and weekends, and days on which the
2002 Football World Cup matches were held were
also included in the regression models as indica-
tor variables.
It was not possible to estimate the effect of
airborne allergens (like pollen and fungi) in rela-
tion to air pollutants, since no systematic records
were found in Rio de Janeiro.
To investigate respiratory infection epidem-
ics, we drew on records for paediatric hospital
admissions due to pneumonia in the city of Rio
de Janeiro from April 2002 to March 2003, ob-
tained from the database of the Unified National
Health System (DATASUS; http://www.datasus.
gov.br). Diagnoses of pneumonias were selected
according to the ICD, 10th revision (ICD-10: J12
to J18) 12. The methodology used in the determi-
nation of epidemic periods was similar to that
reported by Braga et al. 13. Adjustment of this
variable used cubic polynomials for each epi-
demic period.
Acute respiratory manifestations related to air
pollutants can display several days of lag in rela-
tion to exposure. This study analysed the air pol-
lution levels on the day of the paediatric visit (D0)
and the three previous days (D1, D2, D3). The cu-
mulative effect was evaluated with the running
means of the pollutant levels from two to seven
days (mm2, mm3, mm4, mm5, mm6, mm7).
Poisson regression equations directly pro-
duce relative risk values. In this paper risk values
correspond to an increase of 10µg/m3 in each pol-
lutant level analysed separately, with the excep-
tion of CO, for which an increase of 1,000µg/m3
was considered. A 5% significance level was ad-
opted for the study. Results were also reported
as percentage variation in paediatric visits.
The study protocol was submitted to the Re-
search Ethics Committee of the Social Medicine
Institute at the State University of Rio de Janeiro
and was approved at a meeting held on 19 June
2002.
Results
From April 2002 to March 2003, there were 45,595
emergency paediatric visits due to respiratory
disorders. Symptoms of lower airways obstruc-
tion accounted for approximately 42% of all visits
due to lower airways symptoms. In relation to
children’s age, those under 2 years of age com-
prised 2,841 visits and those from aged between 2
and 6 and over 6 comprised 2,893 and 1,067 visits,
respectively.
During the study period there was no viola-
tion of the air quality standards recommended
by the National Environmental Commission
(CONAMA). The CONAMA resolution states that
the primary standards are those pollutant con-
centrations that if exceeded may cause harmful
effects on the exposed population. The recom-
mended primary limit for PM10 is 150µg/m3, for
O3 is 160µg/m3, for NO2 is 320µg/m3, and for
CO 10,000µg/m3 14. Table 1 shows the descrip-
tive statistics for the environmental and health
variables.
The Pearson correlation coefficients between
air pollutants (with the exception of CO and O3)
were positive and statistically significant. The
highest value was 0.33, between CO and PM10.

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Moura M et al.
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Cad. Saúde Pública, Rio de Janeiro, 25(3):635-644, mar, 2009
In children less than 2 years of age, an in-
crease of 10µg/m3 in the environmental concen-
tration of PM10 was associated with an increase of
nearly 7% in the demand for emergency paediat-
ric care due to airways obstruction (p < 0.01). The
same value for O3 exposure led to a smaller effect,
some 3%, in the same age bracket, with marginal
statistical significance (p < 0.06). The estimates
of acute respiratory effects in the children as a
whole and in the other age groups did not show
positive or statistically significant associations.
Figure 1 provides graphic representation of
the percentage variations in all emergency pae-
diatric visits due to the symptoms of bronchial
obstruction in children less than 2 years of age.
All the results are summarized in Table 2.
Discussion
The results suggest that exposure to air pollut-
ants was associated with a significant increase
in emergency paediatric visits due to symptoms
of bronchial obstruction in children under the
age of 2.
Statistical analysis in ecological studies with
daily time series data, considering long and me-
dium-term temporal variations, requires that the
series be sufficiently long for the phenomena to
be shown and the results unbiased. The observa-
tion period, with a maximum of 262 days for the
majority of the pollutants, was the principal limi-
tation in this study, although gaps in monitoring
of pollutants were not related to the air pollution
levels.
Farhat et al. 15, Atkinson et al. 16 and Lin et
al. 17 found positive and significant associations
between exposure to air pollutants and symp-
toms of bronchial obstruction in children, with-
out taking age into account. Conversely, in this
study, the absence of a significant result when
all age ranges were analysed together may have
been due to a dilution of the effects since the
outcome included the entire paediatric popula-
tion.
The impact of the exposure to PM10 was con-
centrated in children under 2. This age bracket
has specific characteristics that distinguishes it
from others ages. Therefore, our findings high-
light the importance of this specificity in the
outcome. One hypothesis is that air pollution
did not influence the demand for emergency
paediatric care due to bronchial asthma (a com-
mon immunological disease in older children).
On the other hand, in children under 2 years of
age, the demand for medical care for symptoms
of bronchial obstruction, frequently associated
with viral agents in this age group, was associated
with PM10 and also with O3 (although a weaker
association in the latter case). One can conclude
Table 1
Descriptive statistics for environmental variables and emergency paediatric visits due to symptoms of bronchial obstruction, by age range, between April 2002
and March 2003.


n

Percentage of
imputed data
Mean
(SD)
Minimum p25 p50 p75 Maximum
Total
Years
0-2
2-6
6-12
Temperature
Minimum
Average
Maximum
Humidity (%)
Rainfall (mm)
PM10 (µg/m3)
CO (1,000µg/m3)
NO2 (µg/m3)
O3 (µg/m3)
262

262
262
262

365
365
365
365
365
262
262
250
248
0

0
0
0

0
0
0
0
0
21.58 (10.49)

8.22 (5.4)
8.44 (4.52)
3.36 (2.39)

22.14 (2.97)
26.31 (3.08)
31.16 (4.04)
76.42 (8.11)
3.59 (10.30)
34.67 (12.49)
1.37 (0.34)
62.78 (32.96)
36.78 (21.75)
4

0
0
0

15
18.01
19
52.58
0
11.22
0.35
9.6
4
14

4
5
2

19.8
24.34
29
70.75
0
25.65
1.17
38.5
19.87
20

7
8
3

22.5
26.36
31.3
76.37
0
32.82
1.39
59
31.85
27

10
11
5

24.4
28.64
34
81.54
0.72
41.53
1.6
81.45
50.17
61
31
23
12
28.6
32.7
40
95.5
76.87
79.04
2.38
209.8
123.9
6.11
6.87
19.6
4.43
n: total number of observation days; SD: standard deviation; p: percentile.

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AIR QUALITY AND EMERGENCY CARE IN CHILDREN WITH BRONCHIAL OBSTRUCTION
639
Cad. Saúde Pública, Rio de Janeiro, 25(3):635-644, mar, 2009
that the reduced dimensions of airways in small-
er children, exacerbating the clinical manifesta-
tions of viral infection, made these children more
susceptible to the effects of pollutants than the
immune alterations characteristic of bronchial
asthma. This result can also be explained by the
parents’ greater concern over health problems in
younger children, demanding immediate medi-
cal care, even for less severe cases. On the other
hand, in older children, the respiratory symptoms
that can appear after exposure either were not se-
vere enough to require emergency care or were
treated later, outside the observation period.
Few studies have taken childhood anatomi-
cal and functional variations into consideration,
categorizing the respiratory effects of air pollut-
ants by age bracket. This limits a broad evalua-
tion of the consistency of results. Braga et al. 18,
in São Paulo, Brazil, investigated hospital admis-
sions due to respiratory causes according to four
age groups of children and adolescents. There
were more admissions for increased exposure to
PM10, O3, SO2, CO, and NO2 among children aged
under 2, equivalent to an interquartile interval. A
greater effect occurred with PM10, and with the
exception of O3, it was possible to reject the null
hypothesis with 99.9% probability. However, the
study did not analyse the respiratory diagnoses
related to the admissions, which precludes com-
parison with our study in Jacarepaguá.
Figure 1
Percentage variation (RR) and 95% confi dence intervals for paediatric visits due to obstructive bronchial symptoms in children less than 2 years of age.
1a) PM10 1b) NO2
1c) CO 1d) O3
Note: effects on the same day (D0), 1 day later (D1), 2 days later (D2), 3 days later (D3), and the moving mean of the concentrations of pollutants for 2, 3, 4, 5,
6, and 7 days (mm2, mm3, mm4, mm5, mm6, mm7, respectively).