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Air pollution may pose significant risks to newborns, children
Exposure to air pollution is associated with an increased risk for death among babies and reduced lung function in childhood, according to two studies presented at the European Respiratory Society International Congress.
“Air pollution affects 100% of the population, as it cannot be avoided, and these studies highlight the harmful effects that are linked to being exposed to dirty air from the very beginning of our lives. Lots of previous research has shown that in the long term, outdoor air pollution can reduce life expectancy, affect lung development, increase asthma incidence and lead to other chronic respiratory diseases,” Jørgen Vestbo, DrMedSci, FRCP, FERS, FMedSci, chair of the European Respiratory Society’s Advocacy Council and professor of respiratory medicine at the University of Manchester, United Kingdom, who was not involved in either study, said in a press release. “Breathing is the most basic human function required to sustain life. We cannot give up the fight for the right to breathe clean air, and we must continue to apply pressure on policymakers to ensure that the maximum pollutant levels indicated by WHO are not breached across our cities and towns in order to protect the health of young babies, as well as the wider population.”
Increased mortality in babies
In the first study, Sarah Kotecha, PhD, from the department of child health at Cardiff University School of Medicine in the United Kingdom, and colleagues assessed associations between particulate matter with aerodynamic diameter of 10 µm or less (PM10), nitrogen dioxide (NO2) and sulfur dioxide (SO2) with all-cause mortality in nearly 8 million babies born between 2001 and 2012 in England and Wales.
“Too many previous studies were small, especially for the U.K. population, so they could not account for other important factors, such as social deprivation. So, we first wanted to establish the association between different air pollution and neonatal deaths (up to 28 days of age) and postneonatal deaths (from 1 to 12 months of age) but also thought that neonatal death would occur via pollution affecting the pregnant mother and postneonatal death is more likely to occur via the pollution acting on the baby,” Kotecha wrote in an email to Healio Pulmonology.
The researchers found that when compared with babies living in the least polluted areas, the risk for death was 24% to 43% higher for infants, 21% to 38% higher for neonates and 32% to 54% higher for babies aged 1 to 12 months living in the most polluted areas. After adjustment for confounders, including deprivation, birth weight, maternal age, sex and multiple births, the risk for infant death was 7% higher with increased exposure to NO2, 4% higher with increased exposure to PM10 and 19% higher with increasing exposure to SO2. Likewise, the risk for postneonatal death increased by 11% for NO2, 12% for PM10 and 15% for SO2. The risk for neonatal death, however, increased by 21% with SO2 but was not significantly associated with NO2 or PM10.
“The results were surprising, as SO2 increased neonatal deaths far more than NO2 or PM10, suggesting that the pollutants act differentially on the baby, either directly (for postneonatal deaths) or exposure of the mother leads to increased deaths of the baby, which is an important finding,” Kotecha wrote in an email to Healio Pulmonology. “We really need to protect both babies, which is the obvious message currently that the press reports on regularly, but we should also be protecting pregnant mothers from such exposure, as the SO2 could potentially affect the unborn baby’s outcome.”
Studies in other large cohorts are now needed to confirm the findings, according to Kotecha.
“Ideally, we would like to understand why SO2 affects the baby via the mother — what are the products that are formed that potentially go to the baby via the mother’s placenta? If we can understand that, we can then try to stop this from occurring by using antioxidants, for example. This is speculative but will need further investigation,” she said.
Reduced lung function in children
In the second study, Anna Hansell, MB, BChir, PhD, professor in environmental epidemiology at the University of Leicester and visiting professor at Imperial College London, and colleagues evaluated the effects of primary local, road and long-range PM10 on lung development and growth as assessed by each trimester of pregnancy as well as during infancy and childhood in nearly 14,000 participants in the U.K. Avon Longitudinal Study of Parents and Children.
From 1990 to 2008, the researchers calculated exposures to PM10 for each trimester and at ages 0 to 6 months, 7 to 12 months and then annually up to age 15 years. FEV1 and FVC were measured at ages 8 and 15 years, with results adjusted for age, sex and height.
On average, children were exposed to 1 µg/m3 of PM10 derived from road traffic, although exposure varied from 0 µg/m3 to 8 µg/m3 during the periods measured. For every 1 µg/m3 increase in exposure to PM10 from road traffic during the first trimester, lung function was reduced by 0.8%, which equated to an average reduction of 14 mL in FEV1 and 16 mL in FVC by age 8 years.
Similar associations were noted for exposure to traffic PM10 during the second and third trimesters, throughout the whole pregnancy or up to age 8 years, and there was a significant association between reduced lung function and exposure to PM10 from all sources during the third trimester.
“Our findings suggest that air pollution exposure before we are born will affect development of the lung, and these adverse events continue with exposures in early childhood affecting lung function at age 8 years. The effects were much more striking for particulates from road traffic,” Hansell wrote in an email to Healio Pulmonology.
Notably, however, results demonstrated no relationship between PM10 and lung function at age 15 years.
“We were surprised that the effects became undetectable by age 15 years, but other studies in Europe have also found this. One reason may be that air pollution decreased over the time period of the study. Another reason may be that the effects of air pollution are relatively small and children may outgrow them by age 15,” Hansell said. “However, another study I published with colleagues earlier this year of U.K. adults showed associations of air pollution with lower lung function in adults, suggesting that air pollution has negative impacts on the lung throughout life.”
This study, she added, shows how important reducing air pollution exposure, especially road traffic exposures, is for children’s respiratory health.
“The average effects were relatively small but may have larger impacts on children whose lungs are sensitive. Also, our study suggested higher effects in children from lower socioeconomic backgrounds and whose mothers smoked,” Hansell said. “However, we would still encourage children to exercise outdoors (except during very high levels/air pollution episodes), as the beneficial effects of exercise outweigh the smaller impacts of air pollution.”
She also noted that further analyses are in the works to see if the researchers “can pinpoint a specific sensitive time window during pregnancy” and to evaluate other air pollutants in future studies. – by Melissa Foster
References:
Hansell A, et al. Abstract OA482.
Kotecha S, et al. Abstract PA297. Both presented at: European Respiratory Society International Congress; Sept. 28-Oct. 2, 2019; Madrid.
For more information:
Anna Hansell, MB, BChir, PhD, can be reached at ah618@leicester.ac.uk.
Sarah Kotecha, PhD, can be reached at kotechasj@cardiff.ac.uk.
Disclosures: One author for Abstract PA297 reports receiving funding from the Medical Research Council. The Avon Longitudinal Study of Parents and Children, also known as the Children of the 90s, receives core funding from the Medical Research Council, the Wellcome Trust and the University of Bristol. Kotecha and Hansell report no relevant financial disclosures.