Association between exposure to particulate matter and hospital admissions for respiratory disease in children

Abstracts

The aim of this study was to estimate the association between exposure to particulate matter less than 2.5 microns in diameter and hospitalization for respiratory disease. It was an ecological time series study with daily indicators of hospitalization for respiratory diseases in children up to 10 years old, living in Piracicaba, SP, Southeastern Brazil, between August 1, 2011 and July 31, 2012. A generalized additive Poisson regression model was used. The relative risks were RR = 1.008; 95%CI 1.001;1.016 for lag 1 and RR = 1.009; 95%CI 1.001;1.017 for lag 3. The increment of 10 μg/m³in particulate matter less than 2.5 microns in diameter implies increase in relative risk of between 7.9 and 8.6 percentage points. In conclusion, exposure to particulate matter less than 2.5 microns in diameter was associated with hospitalization for respiratory disease in children.

Pneumonia; Asthma; Respiratory Tract Diseases; Air Pollutants; Air Pollution; Particulate Matter; Child Health; Time Series Studies

O objetivo desse estudo foi estimar a associação entre exposição a material particulado com menos de 2,5 micra de diâmetro aerodinâmico e internações por doenças respiratórias em crianças. Foi realizado estudo ecológico de séries temporais com indicadores diários de internação por doenças respiratórias, em crianças de zero a dez anos de idade, residentes em Piracicaba, SP, entre 1º de agosto de 2011 e 31 de julho de 2012. Utilizou-se modelo aditivo generalizado da regressão de Poisson. Os riscos relativos foram RR = 1,008; IC95% 1,001;1,016 para o lag 1 e RR = 1,009; IC95% 1,001;1,017 para o lag 3. O incremento de 10 μg/m ³ de material particulado com menos de 2,5 micra de diâmetro implicou aumento no risco relativo entre 7,9 e 8,6 pontos percentuais. Concluiu-se que a exposição ao material particulado com menos de 2,5 micra de diâmetro aerodinâmico esteve associada às internações por doenças respiratórias em crianças.

Pneumonia; Asma; Doenças Respiratórias; Poluentes do Ar; Poluição do Ar; Material Particulado; Saúde da Criança; Estudos de Séries Temporais

Con el objetivo de estimar la asociación entre exposición al PM2.5 e internaciones por enfermedades respiratorias en niños, fue realizado estudio ecológico de series temporales con indicadores diarios de internación por enfermedades respiratorias, en niños de cero a diez años de edad, residentes en Piracicaba, SP (período entre 1° de agosto de 2011 y 31 de julio de 2012. Se utilizó modelo aditivo generalizado de la regresión de Poisson. Los riesgos relativos fueron RR= 1,008; IC95% 1,001; 1,016 para el lag 1 y RR= 1,009; IC95% 1,001; 1,017 para el lag 3. El incremento de 10 μg/m3 de PM2.5 implicó aumento en el riesgo relativo entre 7,9 y 8,6 puntos porcentuales. Se concluyó que la exposición al material particulado con menos de 2,5 micras de diámetro aerodinámico estuvo asociada con las internaciones por enfermedades respiratorias en niños.

Neumonía; Asma; Enfermedades Respiratorias; Contaminantes Del Aire; Contaminación Del Aire; Material Particulado; Salud del Niño; Estudios de Series Temporales

INTRODUCTION

Respiratory disease may be associated with factors such as air pollution, both that produced by motor vehicles and that form burning biomass. ^{3 , 5 , 7}

Data from the Brazilian Ministry of Health report more than 70 thousand hospitalizations in 2011 for children aged under 10, costing more than R$ 60 million (1 US$ ≈ R$ 2.00). ^a

Among the pollutants implicated in hospitalizations for respiratory disease in children, particulate matter less than 10 microns in diameter ⁷ stands out, especially that fraction which is less than 2.5 microns in diameter. ^{3 , 5}

Brazil plays an important role in emitting air pollutants due to biomass burning. Preliminary data of the 2012 to 2013 cane sugar harvest predict that 600 thousand tons will be milled, 56.0% in the state of Sao Paulo. ^b In Piracicaba, SP, sugar cane plantations cover around 80.0% of the surface, generating large quantities of particulate matter when the cane is burnt.³

The municipality of Piracicaba is one of the main producers of sugar and sugar cane alcohol in the world and is responsible for emissions of gases and particulates into the atmosphere when the sugar cane is burnt.

The aim of this study was to estimate the association between exposure to PM_2.5and hospitalizations in children due to respiratory disease.

METHODS

This was an ecological time series study, with daily indicators of hospitalizations for respiratory disease (ICD 10: J12.0 to J18.9, J45.0, J45.1, J45.8, J45.9 and J46), in children aged from zero to ten years in Piracicaba, from August 1, 2011 to July 31, 2012. These data were obtained from the Datasus.¹Estimated daily levels of carbon monoxide (CO in ppb), ozone (O₃in μg/m³), nitrogen oxides (NO_xin μg/m³) and particulate matter (PM_2.5in μg/m³) were obtained from the CATT-BRAMS system. ^{4 , 6} The data on temperature and humidity were obtained from the ESALQ-USP web site ^c and the apparent temperature was calculated using temperature and humidity. ²

Piracicaba is located at latitude 22º43’ S and longitude 47º39’ W, at an altitude of 547 meters. It is 164 km from the state capital and 75 km from Campinas. The territory covers around 1,400 km²and has a little over 350 thousand inhabitants. There were an estimated 199 thousand automobiles and motorcycles, and 12 thousand buses and vans in 2012 (IBGE). ^d

Pearson’s correlation test was used to evaluate possible correlations between hospitalizations and estimated levels of PM_2.5.

The effects of exposure to air pollution can lead to hospitalization on the same day or on following days. Thus, the effects on the respiratory apparatus were investigated on the day of hospitalization ( lag 0) and on the five following days ( lag 1 to lag 5). The generalized additive Poisson regression model was used as the outcome is a discrete, quantitative variable. The results of risk of hospitalization refer to exposure to PM_2.5adjusted for other pollutants and for the apparent temperature. The Statistica v7 program was used for the analyses.

The estimated effects were relative risk (RR), corresponding to an increment of 10 μg/m³in the levels of PM_2.5. The RR were converted into percentage increases. A level of significance of 5.0% was adopted in the analyses.

RESULTS

In individuals aged zero to ten years, there were 437 hospitalizations for respiratory disease. The daily mean was 1.2 (sd = 1.3), minimum 0.0 and maximum 8.0. The mean daily concentration of PM_2.5was 28.6 µg/m³(sd = 16.7) and it did not exceed the limits set by the CETESB. ^e Minimum and maximum values were 1.0 and 113.0 µg/m³respectively. The daily levels exceeded the established level on some days, reaching the regular standard of air quality. The interquartile difference in PM_2.5was 17.2 µg/m³and the mean daily apparent temperature was 19.8ºC (sd = 3.2). Hospitalizations were positively correlated with PM_2.5(r = 0.12; p < 0.05). Apparent temperature showed negative correlation with PM_2.5(r = -0.08; p > 0.05) and with hospitalizations (r = -0.20; p < 0.01).

The coefficients of regression and the respective standard errors for PM_2.5in each lag showed significant p values for lags 1 and 3 after adjusting for other pollutants and for apparent temperature, and controlled for day of the week and season.

The relative risks and their respective 95% confidence intervals showed a positive association between hospitalizations and PM_2.5(RR = 1.008; 95%CI 1.001;1.016 for lag 1 and RR = 1.009; 95%CI 1.001;1.017 for lag 3). The increase of 10 μg/m³of PM_2.5meant an increase of between 7.9 ( lag 1) and 8.6 ( lag 3) percentage points in the relative risk ( Figure ).

Figure
. Relative risk of respiratory disease in children under 10 and respective 95% confidence intervals for the pollutant PM_2.5for each lag . Piracicaba, SP, August 1, 2011 to July 31, 2012.

DISCUSSION

The CATT-BRAMS ^{4 , 6} system used in this study considers the dynamics of the atmosphere. It is a mathematical model covering South America which considers the emission and transport of different gases and aerosol particulates, obtained by satellites that monitor the burning, providing daily estimates for different pollutants. One of the advantages of using this model is its application in cities where there are no pollutant measuring stations. The use of data estimated by this system, validated by Ignotti et al, ⁵ enables the costs of research to be lowered and makes the process of analyzing the effects of atmospheric pollution on health easier.

Hospitalizations for respiratory disease in children under ten were positively and significantly associated with PM_2.5one day and three days after exposure.

Epidemiological studies show that exposure to polluting gases and particulate matter is associated with higher incidence of symptoms in the lower respiratory tract, such as coughing, dyspnea and wheezing, especially in children. ¹

In the municipality of Piracicaba, SP, in addition to pollutants emitted by burning fossil fuels, sugar cane is burnt between April and November, releasing particulate matter and gases into the atmosphere. According to Cançado et al, ³ pioneers in studies in that city, burning the cane fields in the pre-harvest increases atmospheric pollution in the region. Ignotti et al, ⁵ assessing atmospheric pollution from burning biomass in the Amazonian region of Brazil, showed a positive association between exposure to PM_2.5and the occurrence of respiratory disease, especially in the most vulnerable age groups (the elderly and children < 5 years old).

Application of Sao Paulo law no. 11.241/02, ^f which deals with the gradual elimination of the practice of burning sugar cane, was not evaluated, nor were its possible social implications.

This study observed a negative correlation between hospitalization and apparent temperature, which takes into consideration physiological experience of exposure combined with humidity and temperature. This enables the effect of these variables on the individual’s health to be evaluated more effectively. ²

Motor vehicles can contribute to the release of pollutants. These, together with pollutants released from burning can sugar, contribute to increasing hospitalization in the winter, when there is lower humidity and temperatures. This affects the dispersion of atmospheric pollution.

A limitation of this study could be the fact that the CATT-BRAMS measurements are estimated at an altitude of 40m and not closer to the ground, where concentrations may be different.

To conclude, exposure to particulate matter smaller than 2.5 microns in diameter (PM_2.5) was associated with hospitalizations for respiratory disease in children.

REFERÊNCIAS

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Publication Dates

• Publication in this collection
  Dec 2013

History

• Received
  28 Jan 2013
• Accepted
  19 Aug 2013