Elsevier

Environmental Research

Volume 106, Issue 1, January 2008, Pages 96-100
Environmental Research

Winter air pollution and infant bronchiolitis in Paris

https://doi.org/10.1016/j.envres.2007.05.003Get rights and content

Abstract

Respiratory syncytial virus (RSV) is one of the most common respiratory pathogens in infants and young children. It is not known why some previously healthy infants, when in contact with RSV, develop bronchiolitis whereas others have only mild symptoms. Our study aimed to evaluate the possible association between emergency hospital visits for bronchiolitis and air pollution in the Paris region during four winter seasons.

We included children under the age of 3 years who attended emergency room services for bronchiolitis (following standardized definition) during the period 1997–2001. Two series of data from 34 hospitals, the daily number of emergency hospital consultations (n=50 857) and the daily number of hospitalizations (n=16 588) for bronchiolitis, were analyzed using alternative statistical methods; these were the generalized additive model (GAM) and case-crossover models.

After adjustments for public holidays, holidays and meteorological variables the case-crossover model showed that PM10, BS, SO2 and NO2 were positively associated with both consultations and hospitalizations. GAM models, adjusting for long-term trend, seasonality, holiday, public holiday, weekday and meteorological variables, gave similar results for SO2 and PM10.

This study shows that air pollution may act as a trigger for the occurrence of acute severe bronchiolitis cases.

Introduction

The short-term effects of air pollution on humans are assessed using time-series studies and panel studies. Time-series studies have shown broadly consistent associations between air pollutants and related outcomes such as total mortality, cardiorespiratory mortality and hospital admissions. Whereas most studies have focused on the general population and elderly subjects, there have been few on children (Pope, 2000; WHO Task Group, 2004; Health Effect Institute, 2003; Ségala, 1999). Conversely, there have been numerous panel studies on mostly asthmatic children. Panel studies measure health effects, such as symptoms, on an individual basis (Desqueyroux and Momas, 1999). In epidemiology, only few studies focused on the role of air pollution as a risk factor for specific respiratory infections, such as respiratory syncytial virus (RSV) bronchiolitis (Zamorano et al., 2003; Karr et al., 2006). However, experimental data have shown that air pollutants affect lung immune responses and inflammatory reactions and that these effects may underlie the increased risk for respiratory infections (Becker and Soukup, 1999; Gilmour et al., 2001; Harrod et al., 2003; Lambert et al., 2003).

RSV is one of the most common respiratory pathogens in infants and young children. Most infants develop only mild or no symptoms when in contact with RSV. However, some infants develop RSV bronchiolitis, which is characterized by expiratory wheezing and respiratory distress. This condition presents a major public health problem, as the winter peak periods of RSV virus activity often result in numerous hospital consultations and hospitalizations. Very few studies have assessed bronchiolitis mortality. A US study reported between 171 and 510 bronchiolitis associated deaths per year between 1979 and 1997 among children under 5 years of age (Law et al., 2002).

The aim of our study was to evaluate the association between emergency hospital visits for bronchiolitis and short-term exposure to air pollution in the Paris region during four winter seasons, using our alternative approach. Our null hypothesis was that air pollutants trigger acute severe bronchiolitis.

Section snippets

Study subjects

We included children under the age of 3 years who attended emergency room services for bronchiolitis during the period 1997–2001. Daily bronchiolitis data were obtained from the “Epidémiologie et Receuil des Bronchiolites en Urgence pour la Surveillance” (ERBUS) database (Thelot et al., 1998). This contains data, available every year, for the period between 15th October and 15th January from 43 hospitals within greater Paris. Physicians reviewed the clinical records of all daily visits and

Results

We found a strong correlation between the levels of the pollutants during the 4 years studied. Temperature, rain and wind were negatively correlated with the pollutants, whereas atmospheric pressure was positively correlated with them (Table 1, Table 2).

Several environmental variables differed for the four winter seasons. The mean concentrations of the four pollutants were lower and the mean minimal temperature was higher during the 2000–2001 winter season than during the three previous winter

Discussion

This study shows short-term relationships between air pollutants and the daily numbers of emergency hospital consultations and hospitalizations for bronchiolitis.

It is not known why some previously healthy infants, when in contact with RSV, develop bronchiolitis whereas others have only mild symptoms (Sigurs et al., 1995). Only few studies, with conflicting results thus far, have investigated the relationship between air pollution and bronchiolitis. A Spanish study (Zamorano et al., 2003) had

Acknowledgment

The authors would like to thank the “Délégation à l’Information Médicale et à l’Epidémiologie” of the “Assistance Publique-Hôpitaux de Paris” for providing access to the bronchiolitis data.

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    Funding: The study was supported by the “Conseil National Scientifique” of ANTADIR.

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