Air pollution and acute respiratory infections among children 0-4 years of age: an 18-year time-series study

Abstract

Upper and lower respiratory infections are common in early childhood and may be exacerbated by air pollution. We investigated short-term changes in ambient air pollutant concentrations, including speciated particulate matter less than 2.5 μm in diameter (PM2.5), in relation to emergency department (ED) visits for respiratory infections in young children. Daily counts of ED visits for bronchitis and bronchiolitis (n = 80,399), pneumonia (n = 63,359), and upper respiratory infection (URI) (n = 359,246) among children 0-4 years of age were collected from hospitals in the Atlanta, Georgia, area for the period 1993-2010. Daily pollutant measurements were combined across monitoring stations using population weighting. In Poisson generalized linear models, 3-day moving average concentrations of ozone, nitrogen dioxide, and the organic carbon fraction of particulate matter less than 2.5 μm in diameter (PM2.5) were associated with ED visits for pneumonia and URI. Ozone associations were strongest and were observed at low (cold-season) concentrations; a 1-interquartile range increase predicted a 4% increase (95% confidence interval: 2%, 6%) in visits for URI and an 8% increase (95% confidence interval: 4%, 13%) in visits for pneumonia. Rate ratios tended to be higher in the 1- to 4-year age group compared with infants. Results suggest that primary traffic pollutants, ozone, and the organic carbon fraction of PM2.5 exacerbate upper and lower respiratory infections in early life, and that the carbon fraction of PM2.5 is a particularly harmful component of the ambient particulate matter mixture.

Keywords: air pollution; bronchiolitis; children; lower respiratory infection; pneumonia; upper respiratory infection.

Figure 1.

Season-specific (circles = March–October; triangles = November–February) rate ratios per 1–interquartile range increase in 3-day moving average population-weighted ambient air pollutant concentrations for A) pneumonia and B) upper respiratory infections, Atlanta, Georgia, 1993–2010. Bars, 95% confidence intervals. CO, carbon monoxide; EC, elemental carbon fraction of PM_2.5; NH₄, ammonium fraction of PM_2.5; NO₂, nitrogen dioxide; NO₃, nitrate fraction of PM_2.5; O₃, ozone; PM₁₀, particulate matter less than 10 μm in diameter; OC, organic carbon fraction of PM_2.5; PM_2.5, particulate matter less than 2.5 μm in diameter; SO₄, sulfate fraction of PM_2.5.

Figure 2.

Rate ratios per 1–interquartile range increase in ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO), particulate matter less than 2.5 µm in diameter (PM_2.5), and the elemental carbon fraction of PM_2.5 (EC) from single-pollutant models and joint-effects models (for a combined increase in the interquartile range of all pollutants listed) for A) pneumonia and B) upper respiratory infection, Atlanta, Georgia, 1998–2010. All estimates are based on 4,186 observation days with measurements for all 5 pollutants. Bars, 95% confidence intervals.

Figure 3.

Rate ratios per 1–interquartile range increase in components of particulate matter less than 2.5 μm in diameter (PM_2.5) from single-pollutant models and from a multipollutant model including the sulfate fraction of PM_2.5 (SO₄), nitrate (NO₃), elemental carbon (EC), and organic carbon (OC) for A) pneumonia and B) upper respiratory infection, Atlanta, Georgia, 1998–2010. Bars, 95% confidence intervals.