Study Links Air Pollution Exposure During Pregnancy to Reduced Lung Function in Childhood

Jakob Usemann MD, PhD

Credit: UKBB

Higher levels of exposure to PM_2.5 pollution during the prenatal period is associated with reduced lung volume and airflow limitation, according to recent findings, indicating that in utero lung development may be most sensitive to air pollution exposure.¹

These findings were the result of new research which was led by Jakob Usemann MD, PhD, from the department of respiratory medicine at the University Children's Hospital Zurich in Switzerland. Usemann et al. noted that increasingly, there is an awareness that pollution exposure in the early period of a child’s life can lead to potential long-term impacts on lung function trajectories throughout childrens’ lives.²

This new analysis was carried out to address knowledge gaps resulting from most prior research, as those in previous studies had been exposed to higher levels of pollution as opposed to moderate levels.

“We hypothesize that prenatal air pollution exposure is associated with stronger deficits in forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) than postnatal exposure,” Usemann and colleagues wrote.¹

Study Design

The investigators titled this study LUIS, and they conducted their research in the period between 2013 - 2016. They evaluated those who were schoolchildren and aged 6-17 years from Zurich, Switzerland, using a cross-sectional population-based trial design that was also then worked into a respiratory health promotion campaign.

This campaign invited all schools within Zurich to take part, implementing a study bus which contained standardized lung function equipment that also visited participating schools. Field workers in the study bus would visit and assess children's weight and height, carrying out tears of lung function and providing subjects with a short digital questionnaire.

Questionnaires for parents were gathered by the research team at the same time, with parents detailed responses. The investigators looked at data drawn from statistical models and from MeteoSwiss with the aim of assessing residential pollutant exposure levels and estimating mean exposure in different periods of time.

Some of the periods evaluated by the research team included the entire course of a pregnancy, the course of each trimester, the initial year of life, and the years in which children are in preschool (birth to 6.5 years). Fine-scale models for prediction were used to determine levels of residential NO₂ and PM_2.5, with the team looking at information spanning 2005-2016 for NO₂ and 2003-2013 for PM_2.5.

Prior residential addresses and current ones were discussed by parents, and these were then geocoded by the investigators. They linked environmental exposures to NO₂ and PM_2.5 to each child's home address, accounting for shifts in participant addresses and weighting exposures based on their time they had spent at each location.

The research team used spirometry tests to look into outcomes such as FEV1, FVC, FEV1/FVC ratio, and FEF25%-75%. Additional elements were also evaluated by the team, including the child's weight, age, ethnicity, maternal smoking at the time of pregnancy, parental habits related to smoking, height, body mass index, sex, active smoking, current respiratory infections, asthma status, lung function test timing, socioeconomic status (using the Swiss socioeconomic position index), presence of asthma among parents, and existence of pets in one’s household.

The investigators evaluated average NO₂ and PM_2.5 concentrations, calculating them individually for the 7 days prior to the provided lung function tests.

Conclusions

The investigators had involved 2,182 children as participants, all of whom were between the ages of 6 - 17 years. Exposure to air pollutants at the time of pregnancy was shown by the team to have been linked to diminished pulmonary function among children in school age.

There was a notable rise reported to be among 12-year-olds of 10 µg/m³ in levels of PM_2.5 during pregnancy that the research team linked to a 55 mL reduction in FEV1 (95% CI −84 to −25 mL) as well as a 62 mL FVC reduction (95% CI −96 to −28 mL). Such impacts were also shown to have varied with age, with the team finding that it was more pronounced among younger children and less so among those who were older.

There was not a correlation between postnatal PM_2.5 exposure and diminished lung function, the investigators determined. They added that no relationship had been observed between NO₂ exposure and pulmonary function.

“The study is limited by the cross-sectional design and only spirometry-based assessment of lung function, which did not allow us to assess the adverse effects of air pollution on lung growth or on static lung volumes,” they wrote. “Furthermore, in this field study, objective measures of second-hand smoking or active smoking were not obtained.”

References

1. ^{Usemann J, Mozun R, Kuehni CE, et al. Air pollution exposure during pregnancy and lung function in childhood: the LUIS study. Pediatr Pulmonol. 2024; 1-12. doi:10.1002/ppul.27169.}
2. ^{Bose S. Air pollution and child lung health: critical thresholds at critical times. Ann Am Thorac Soc. 2022; 19(5): 723-725.}