Babies' exposure to high levels of air pollution in the womb may lead to a type of DNA damage, typically associated with ageing, called telomere shortening, warned a study. Telomeres are the caps at the end of each strand of DNA that protect our chromosomes. Telomere shortening is the main cause of age-related breakdown of our cells and has been linked with cancer and heart disease, cognitive decline, ageing, as well as premature death.