Improved air quality linked to better lung function in children

1. A decrease in common air pollutants from fuel combustion was associated with an increase in lung function in children aged 11 to 15.

Evidence Rating Level: 2 (Good)           

Study Rundown: For many years, the effects of air pollution have been associated with negative health consequences, particularly lung function. Due to stricter emission standards, comprehensive data on air pollution collected in southern California (since 1994) has demonstrated a significant downward trend in common air pollutants from fuel combustion.

This retrospective study analyzed pulmonary function tests from three cohorts of children followed from the ages of 11 to 15 at different times (1994-1998, 1997-2001, and 2007-2011) in five communities of Southern California. Statistically significant gains in lung function (forced expiratory volume in one second [FEV1] and forced vital capacity [FVC]) were noted with median decreases in nitrogen dioxide, particulate matter less than 10 microns diameter, and particulate matter less than 2.5 microns diameters. This association was maintained when adjusted for gender, ethnicity, smoke exposure (in-utero and passive), several indoor exposures and pets.

This study provided strong objective evidence that current efforts to curb emissions of pollutants are having positive impacts on public health. However, cohorts in this study only included a narrow age range, therefore the long-term benefits on lung function remain unknown. As this study included data collected over 17 years, certain cohorts were tested on different spirometers depending on the availability of devices at that time. As tighter emission standards have likely decreased air pollution throughout the entire country, a true control group (i.e. children exposed to equal amounts of air pollution in all three cohorts) could not be included as a reference point. Future studies could apply similar statistical methods in adults to search for a possible association between air pollution and chronic obstructive pulmonary disease (COPD) among lifetime non-smokers.

Click to read the study in NEJM

Click to read an accompanying editorial in NEJM

Relevant Reading: Pollution & air quality – The Lung Association

In-Depth [retrospective cohort]: 2120 children from five southern California communities were divided in three cohorts from three distinct time intervals: 1994-1998, 1997-2001, 2007-2011. These children were enrolled at the age of 11 and followed with annual lung function tests until the age of 15. The median decrease in nitrogen dioxide and small particulate matter from 1994 to 2011 was associated with statistically significant gains in lung function during the ages of 11 to 15. Every median decrease in nitrogen dioxide was associated with mean growth of 91.4 mL in FEV1 ((P<0.001) and 168.9 mL FVC (P<0.001). Similarly, every median decrease in small particulate matter was also associated with a mean growth in FEV1 and FVC. This association was also maintained when adjusted for factors which frequently confound lung function tests (i.e., ethnicity, in-utero or passive smoke exposure, indoor exposures, presence of pets).

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