Links between early-life air pollution and lung function persist into adolescence

Air pollution can cause a wide range of adverse health effects, including COPD, asthma, low birth weight, cancer, cardiovascular disease, and an increased risk of premature death.

A new study from the University of Copenhagen, Danish Pediatric Asthma Centre, and Herlev and Gentofte Hospital shows that even small differences in exposure to air pollution during pregnancy and the first years of life are associated with poorer lung function in children and adolescents.

“We found that children who were exposed to higher concentrations of air pollution during their mothers’ pregnancy and their first years of life had an increased risk of lower lung function when we measured it at age six,” says the study’s lead author, Marie Pedersen, Associate Professor at the Department of Public Health, University of Copenhagen.

“And the children do not appear to outgrow this difference. Higher concentrations of air pollution were also associated with slightly impaired development of lung function throughout childhood and into adolescence.”

A public health concern

The study is based on detailed data from several hundred pregnant women and their children, collected from pregnancy until the children reached 18 years of age through the Danish Pediatric Asthma Center. Researchers combined detailed calculations of air quality at participants’ home addresses with repeated measurements of the children’s lung function throughout childhood and adolescence.

The study focused on tiny airborne particles known as fine particulate matter (PM2.5) and the gas nitrogen dioxide (NO₂), pollutants that originate from combustion processes such as traffic, industry, wood-burning stoves, and agriculture.

The researchers found that even relatively small differences in air pollution levels around the children’s homes were associated with small but measurable differences in lung function.

For example, exposure during pregnancy to just 2 micrograms more fine particulate matter per cubic metre of air was associated with almost 2 percent lower lung capacity in the six-year-old children.

“For an individual child, such a difference is not noticeable. However, even small average shifts can have a major impact when viewed across an entire population. Since we also found that children exposed to higher levels of air pollution appeared to develop lung function more slowly throughout childhood, there is a risk that this represents a public health issue,” says Marie Pedersen.

“This study adds to the growing body of evidence suggesting that exposure to air pollution, even at relatively low concentrations, is associated with adverse health effects, including respiratory diseases such as asthma and COPD.”

We can do something about it

According to Marie Pedersen, the findings suggest that there may still be health benefits to be gained by further reducing air pollution.

Although air pollution levels in Denmark have declined substantially over recent decades, they remain above the World Health Organization's recommended level of 5 micrograms of fine particulate matter per cubic metre of air. In the study, the annual average concentration was 9.6 micrograms per cubic metre.

At the same time, approximately 75 percent of particulate pollution in Denmark originates from sources outside the country.

“Air pollution is one of the environmental factors where we know many of the sources and can take action. We have already improved air quality in many places, but our results support that further reductions could potentially benefit children’s health. Strengthening efforts to improve air quality at the European level would be advantageous,” says Marie Pedersen.

She adds:

“Air quality, health, and climate change are closely interconnected, so many initiatives aimed at improving air quality will also help reduce greenhouse gas emissions.”

At the same time, she stresses that the study is not a reason for parents to keep children indoors.

“Children should still cycle, play, and be physically active. The message is not that families should be worried in their everyday lives, but rather that as a society we should continue working towards cleaner air.”