Exposure to passive smoking in childhood causes irreversible damage to the structure of children’s arteries, according to a study. The study is the first to follow children through to adulthood in order to examine the association between exposure to parental smoking and increased carotid intima-media thickness (IMT) -- a measurement of the thickness of the innermost two layers of the arterial wall -- in adulthood. It adds further strength to the arguments for banning smoking in areas where children may be present, such as cars.