Research shows that air pollution is slowing the lung growth of children in the UK. Scientists tracked the lung function of more than 5,000 people who were born in and around Bristol in the 1990s. The health of the Children of the 90s cohort was assessed from birth onwards and their lungs were tested as they grew up, at eight and 15 years old and then as adults, aged 24, when their lung function should have reached its maximum.

Prof Anna Hansell, of the University of Leicester, who led the study, said: “Much of the evidence on health effects of air pollution relates to adults or pregnancy, but we think it’s highly plausible it has impacts on growth and development of children.

“Those whose lungs didn’t grow to maximum potential in childhood may be more vulnerable to the respiratory diseases of later life because they have a lower reserve. They are also more vulnerable to poorer health generally. For instance, low lung function in adults is associated with the same level of risk of heart disease as having high cholesterol. Research has also shown that people whose lung health has been affected by air pollution may be at greater risk of heart disease.”

Dr Katie Eminson, also of the University of Leicester and a first author of the study, said: “Lung function was measured using spirometry by trained technicians. Participants were asked to take a deep breath in, then blow out as hard and as fast as possible into a mouthpiece. A machine measured both the amount of air they can breathe out and the speed of that breath, providing an indication of how well their lungs are working.”

The researchers calculated the children’s air pollution exposure in each trimester of pregnancy and then for each year of early childhood. This included particle pollution as well as nitrogen dioxide, a gas that comes mainly from diesel cars and fossil gas boilers.

Hansell said: “We spent literally years creating the particulate air pollution exposure estimates in pregnancy and early life, including sourcing road traffic data from Bristol city council that are not available in the national database.”

The researchers allowed for other factors that can affect children’s health, including premature birth, breastfeeding, parental smoking and home conditions including damp.

They found that breathing more air pollution during pregnancy, infancy and early childhood can slow lung development all the way up to early adulthood. The greatest impact was during adolescence, which is the time when lung growth accelerates.

An earlier study found that air pollution was reducing the growth of children’s lungs in east London. Here, the average nine-year-old’s lungs were between 90 and 100 millilitres smaller than they should be. This is approximately the volume of two hen’s eggs.

Studies on children in Sweden showed that lung growth increased when air quality improved. Reductions in air pollution might have also allowed the Bristol children’s lung growth to return closer to normal rates.

Eminson concluded: “While the effects in individual children are small and unlikely to have immediate clinical consequences, they shouldn’t be dismissed. Because lung function tends to track from childhood into adulthood, small differences early in life may have implications for long-term health. This reinforces the importance of reducing exposures and protecting children’s environments.”