"Our results suggest that telomere length may have potential for use as a biomarker of DNA damage due to environmental exposures and/or chronic inflammation," said the study by John Balmes of University of California, Berkeley, and colleagues.
"Telomeres might also provide new insights into the understanding how pollution exposure leads to adverse health outcomes," the researchers said.
The study included 14 children and adolescents living in Fresno, California – the second-most polluted city in the US.
The researchers assessed the relationship between polycyclic aromatic hydrocarbons (PAHs), a "ubiquitous" air pollutant caused by motor vehicle exhaust; and shortening of telomeres.
As the exposure to PAHs increased, telomere length decreased in linear fashion.
Children and teenagers with asthma were exposed to higher PAH levels than those without asthma, the study showed.
The study adds to previous evidence that air pollution causes oxidative stress, which can damage lipids, proteins, and DNA.
Research has suggested that children may have different telomere shortening regulation than adults, which might make them more vulnerable to the damaging effects of air pollution.