Acute effects of air pollution on pediatric asthma exacerbation: Evidence of association and effect modification

https://doi.org/10.1016/j.envres.2011.01.014Get rights and content

Abstract

We investigated the short-term effects of particulate matter with aerodynamic diameter <10 μg/m3 (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3) on pediatric asthma emergency admissions in Athens, Greece over the period 2001–2004. We explored effect modification patterns by season, sex, age and by the presence of desert dust transported mainly from the Sahara area.

We used daily time-series data provided by the children's hospitals and the fixed monitoring stations. The associations were investigated using Poisson regression models controlling for seasonality, weather, influenza episodes, day of the week and holiday effects.

A 10 μg/m3 increase in PM10 was associated with a 2.54% increase (95% confidence interval (CI): 0.06%, 5.08%) in the number of pediatric asthma hospital admissions, while the same increase in SO2 was associated with a 5.98% (95% CI: 0.88%, 11.33%) increase. O3 was associated with a statistically significant increase in asthma admissions among older children in the summer. Our findings provide limited evidence of an association between NO2 exposure and asthma exacerbation. Statistically significant PM10 effects were higher during winter and during desert dust days, while SO2 effects occurred mainly during spring.

Our study confirms previously reported PM10 effects on emergency hospital admissions for pediatric asthma and further provides evidence of stronger effects during desert dust days. We additionally report severe effects of SO2, even at today's low concentration levels.

Research highlights

► We found adverse effects of exposure to pollutants on pediatric asthma admissions. ► PM10 effects were higher during winter and during desert dust days. ►O3 was associated with asthma admissions among older children in the summer. ►We report severe effects of SO2, even at today's low concentration levels.

Introduction

Studies at current levels of pollutants suggest a causal role of pollutants on various adverse health outcomes (Anderson et al., 2004, Holgate et al., 1999, Katsouyanni et al., 2001, Samet et al., 2000). Recent epidemiological research focuses on the health effects of air pollution on potentially sensitive population subgroups such as children and the elderly in order to better understand the mechanisms of action and identify the most susceptible population groups for the protection and improvement of public health (Anderson et al., 2003, Hoek and Brunekreef, 1993, Peters et al., 1999). Potential determinants of children's susceptibility include the continuing process of lung growth and development, incomplete metabolic systems, immature host defences, high rates of infection with respiratory pathogens and activity patterns that increase exposure to air pollution and to volume of inhaled pollutants (Anderson et al., 2004, Holgate et al., 1999).

Epidemiological research on the health effects of air pollution on children has mainly focused on particles, which have been associated with upper and lower respiratory symptoms in children (Atkinson et al., 2001, Halonen et al., 2008, Sunyer et al., 2003, World Health Organization, 2006 2010). Though viral respiratory tract infections are reported as the major trigger for asthma exacerbations in children, an additive or synergistic effect with ambient air pollutants has been considered (Chauhan et al., 2003). Recently, there has been growing demand for more in-depth investigation of the effects of gaseous pollutants and of the possible factors modifying any observed effects.

Following these research lines we have investigated the acute effects of particulate matter with aerodynamic diameter <10 μ (PM10) and several gaseous pollutants, namely sulfur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3), on emergency hospital admissions for asthma-related diagnosis among children aged 0–14 years in Athens, Greece. We explored possible modification patterns by season, sex and age. In addition, Athens, due to its metropolitan setting and geographical position, provides an opportune case for the investigation of the health effects of air pollution and windblown desert dust particles, which originate mainly from the Sahara area. Hence, we also investigated whether the presence of windblown Sahara dust modifies the association between PM10 and pediatric hospital admissions for asthma.

Section snippets

Data

We collected data on daily counts of pediatric asthma emergency admissions in the three main Children's Hospitals in Athens, covering approximately 85% of pediatric beds of the metropolitan area of Athens, from 2001 to 2004. All of the admissions were for at least one over-night stay. All children admitted with the diagnosis of “asthma” (International Classification of Disease (ICD)-9: 493), “asthmatic bronchitis” or “wheezy bronchitis” (ICD-9: 493.9), aged 0–14 years, living in the greater

Results

Table 1 presents the distribution of the pediatric hospital admissions included in the analysis. During the study period there were 3601 admissions in total for acute asthma-related diagnoses, with a daily mean of three. 63% of these occurred among males and 72% among children aged less than five years. Asthma admissions revealed a distinct seasonal pattern with a higher number of admissions during winter and lower during summer, when children leave the urban area for summer holidays.

The median

Discussion

During the last decade epidemiologic research on the adverse health effects of air pollution has focused on susceptible population subgroups. With respect to children, recent time-series and panel studies have indicated the adverse health effects of exposure to urban air pollution, mainly regarding exposure to particulate matter (Anderson et al., 2004, Atkinson et al., 2001, Barnett et al., 2005, Halonen et al., 2008, Priftis et al., 2007b, Schildcrout et al., 2006, Strickland et al., 2010)

References (45)

  • R.W. Atkinson et al.

    Acute effects of particulate air pollution on respiratory admissions: results from APHEA 2 project. Air pollution and health: a European approach

    Am. J. Respir. Crit. Care Med.

    (2001)
  • A.G. Barnett et al.

    Air pollution and child respiratory health: a case-crossover study in Australia and New Zealand

    Am. J. Respir. Crit. Care Med.

    (2005)
  • B.A. Brumback et al.

    Transitional regression models, with application to environmental time-series

    J. Am. Statist. Assoc.

    (2000)
  • B. Brunekreef et al.

    Epidemiological evidence of effects of coarse airborne particles on health

    Eur. Respir. J.

    (2005)
  • J.E. Clougherty

    A growing role for sex analysis in air pollution epidemiology

    Environ. Health Perspect.

    (2010)
  • R.H. Dougherty et al.

    Acute exacerbations of asthma: epidemiology, biology and the exacerbation-prone phenotype

    Clin. Exp. Allergy

    (2009)
  • European Environmental Agency, 〈http://www.eea.europa.eu/publications/2599XXX/page018.html〉 [accessed 1 November...
  • T. Gotschi et al.

    Comparison of black smoke and PM2.5 levels in indoor and outdoor environments of four European cities

    Environ. Sci. Technol.

    (2002)
  • N. Gouveia et al.

    Respiratory diseases in children and outdoor air pollution in São Paulo, Brazil: a time-series analysis

    Occup. Environ. Med.

    (2000)
  • Greek Ministry of Environment, Energy and Climate Change. Available: 〈http://www.minenv.gr〉 [accessed 7 February...
  • D.W. Griffin

    Atmospheric movement of microorganisms in clouds of desert dust and implications for human health

    Clin. Microbiol. Rev.

    (2007)
  • K. Gyan et al.

    African dust clouds are associated with increased pediatric asthma accident and emergency admissions on the Caribbean island of Trinidad

    Int. J. Biometeorol.

    (2005)
  • Cited by (230)

    View all citing articles on Scopus
    View full text