Prenatal Air Pollution Linked to Impaired Lung Function

Diana Phillips

October 22, 2014

Prenatal exposure to traffic-related air pollution increases the risk for respiratory disease in otherwise healthy children, according to a new report published online October 20 in Thorax.

In a population-based mother–child cohort study set up in several geographic areas in Spain, children exposed to benzene and nitrogen dioxide during the second trimester of pregnancy demonstrated significant reductions in lung function on spirometry testing at preschool age. In addition, the risk for low lung function increased as pollutant exposure increased, according to Eva Morales, MD, PhD, MPH, from the Centre for Research in Environmental Epidemiology, Barcelona, Catalonia, Spain, and colleagues.

The findings are consistent with previous reports of an association between maternal exposure to ambient pollutants and infant lung function and suggest that exposure to traffic-related pollution during the prenatal period may inversely affect the developing lung, the authors write.

The study population included 620 children (mean age, 4.5 years) participating in the Infancia y Medio Ambiente, a network of birth cohorts in Spain that aims to study the role of environmental pollutants in air, water, and diet during pregnancy and early childhood in relation to child growth and development.

To examine the associations between exposures to outdoor air pollution with lung function at preschool age, the investigators developed land-use regression models to estimate residential-based exposures during specific trimesters of pregnancy and postnatal life, as well as recent and current exposures. Spirometry conducted by a trained nurse measured forced vital capacity, forced expiratory volume at 1 second, forced expiratory flow 25% to 75% of forced vital capacity, and peak expiratory flow.

After adjusting for multiple potential confounding variables, including child demographics and factors that had at least marginally significant association with air pollutant levels, "[a] linear inverse relationship was found between residential levels of benzene and NO2 during pregnancy and parameters in spirometry at 4.5 years," the authors report.

Children of mothers who lived in a high–traffic air pollution area for benzene during the second trimester of pregnancy had a 22% higher risk for impaired lung function than those living in less polluted areas, and children of mothers living in a high–traffic air pollution area for nitrogen dioxide during their second trimester had a 30% higher risk for impaired lung function than those from less polluted areas.

Levels of air pollutants during the first year of life were inversely associated with parameters in spirometry at 4.5 years, but the associations were not statistically significant, the authors state. Recent and current exposures were also not associated with significant deficits in lung function.

In stratified analyses, no evidence of statistically different associations for girls and boys emerged, nor were there differences in the association between levels of air pollutants and lung function parameters according to allergic parental status or child's asthmatic status, the authors report.

"To our knowledge, this is the first study examining effects on lung function as early as at preschool age, in relation to residential exposure to traffic-related air pollutants through different windows of susceptibility including specific trimesters of pregnancy and postnatal lifetime periods," according to the authors. The relationship between higher levels of the pollutants and clinically relevant lung function deficits "suggest that exposure to traffic-related air pollutants acting during the prenatal period could adversely impact the developing lung."

The study provides "convincing evidence that prenatal exposures to traffic-related pollution have long-term effects on lung function in otherwise healthy children," Peter D. Sly, MBBS, MD, DSc, from the Queensland Children's Medical Research Institute at the University of Queensland, Royal Children's Hospital, Brisbane, Australia, writes in an accompanying editorial.

"This exposure is potentially avoidable and can be influenced by regulation and legislation. Policy makers need to heed data such as those presented...as limiting exposure to traffic-related pollution during fetal development and early postnatal life is one way that the burden of respiratory disease can be decreased."

Thorax. Published online October 20, 2014. Article full text, Editorial full text

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