New Delhi, Jun 28 (IANS): Early-life exposure to air pollution may have a direct effect on lung health later in life, reveals a study on Friday that underlines the need to reduce pollution.

Scientists at the University of Southern California (USC) found that the link between childhood air pollution exposure and adult bronchitis symptoms such as bronchitis, chronic cough, or congestion or phlegm production not associated with a cold -- persisted even when the researchers adjusted for asthma or bronchitis symptoms early in life.

The study, published in the American Journal of Respiratory and Clinical Care Medicine, included 1,308 Children's Health Study participants with an average age of 32 at their adult assessment.

The results showed that one-quarter of participants had experienced bronchitis symptoms within the previous 12 months.

The findings "suggest that childhood air pollution exposure has more subtle effects on our respiratory system that still impact us in adulthood," said Erika Garcia, Assistant Professor of population and public health sciences at the Keck School of Medicine.

The presence of bronchitis symptoms was associated with exposure between birth and age 17 to two types of pollutants.

One group consists of tiny particles in the air, such as dust, pollen, ash from wildfires, industrial emissions, and products from vehicle exhaust.

The other is nitrogen dioxide -- a byproduct of combustion in automobiles, planes, boats, and power plants that is known to hurt lung function.

The study focussed on exposure in children as they are particularly vulnerable to the effects of air pollution. Their respiratory and immune systems are still developing, and compared to adults, they breathe in more air relative to their body mass.

The team also found that the effect of nitrogen dioxide and particulate matter exposure during childhood on bronchitis symptoms among adults was stronger for those who had been diagnosed with asthma as kids.