Air pollutants harm lung function of preterm-born school-aged children

Key takeaways:

• Percent-predicted FVC went down as PM_2.5, PM₁₀ and nitrogen dioxide exposure levels went up in preterm-born children.
• This relationship was mainly found in children classified as extremely preterm.

Among school-aged children born preterm, heightened current exposure to fine particulate matter and nitrogen dioxide each negatively impacted lung function, according to results published in Thorax.

Further, this patient population had lower lung function with high levels of exposure to particulate matter between 2.5 µm and 10 µm in diameter (PM₁₀) at birth, according to researchers.

“Our study has demonstrated that exposure to traffic-related air pollutants, both perinatally and postnatally, have detrimental association with [percent-predicted FVC] especially for those children born extremely preterm (< 28 weeks’ gestation),” William John Watkins, PhD, senior lecturer and medical statistician at Cardiff University, and colleagues wrote.

In this study, Watkins and colleagues assessed 542 children (51.5% boys) born preterm (≤ 34 weeks’ gestation) now aged 7 to 12 years to find out how ambient air pollutant exposures (fine particulate matter 2.5 µm or less in diameter [PM_2.5], PM₁₀, nitrogen dioxide and sulfur dioxide) are linked to different spirometry measures.

Researchers captured pollution levels at two times (birth and time of spirometry) and estimated spirometry values against these levels through regression models.

Based on gestational age, the total cohort included 99 children born between 23 and 28 weeks’ gestation, 165 children born between 29 and 31 weeks’ gestation and 278 children born between 32 and 34 weeks’ gestation.

In the 23 to 28 weeks’ gestation group, PM₁₀ exposure at birth significantly reduced percent-predicted FVC in the model that accounted for early and current life factors (B = –0.66; P = .016). This relationship was also observed in the 29 to 31 weeks’ gestation group (B = –0.58; P = .027), according to researchers.

Between the children with the lowest PM₁₀ exposures at birth and the children with the highest PM₁₀ exposures at birth, both in the 23 to 28 weeks’ gestation cohort, researchers found a significant difference of 6.95% in percent-predicted FVC (P = .02). In the 29 to 31 weeks’ gestation cohort, the difference was also significant (difference, 6.1%; P = .03).

In terms of the link between current pollutant exposures and spirometry, percent-predicted FVC in children born between 23 and 28 weeks’ gestation was negatively impacted by PM_2.5 (B = –1.19; P = .031) and nitrogen dioxide (B = –0.29; P = .05).

Comparing the children with the highest current PM_2.5 exposures in this gestation group with children with the lowest current PM_2.5 exposures revealed a 5.94% difference in percent-predicted FVC (P = .03). The difference in this measure of lung function between the highest and lowest exposure groups was even larger when evaluating current nitrogen dioxide exposure (difference, 7.44%; P = .05).

Notably, none of the assessed air pollutants had a significant link to percent-predicted FEV₁ or percent-predicted forced expiratory flow between 25% and 75% of vital capacity.

Researchers further reported that averaging the two collected pollutant levels did not result in significant links between any spirometry measure and the four pollutants.

“These data highlight the importance of air quality strategies to reduce any further detrimental impact on lung growth and function in this group of individuals with likely aberrant lung development, and who are already at heightened risk of long-term respiratory morbidity,” Watkins and colleagues wrote.