This article is the second in a series on asthma. The first article identified that the UK is experiencing an ‘epidemic’ of childhood asthma and one of the major culprits is air pollution. This article examines the main causes of air pollution and how they affect the lung health of children from before birth and onwards. It considers the contribution of indoor and outdoor air pollution, how these have changed over time and the unequal effect they may have on vulnerable populations. The nurse’s role is discussed, not only in terms of clinical care, but also as adviser to families and schools on what actions to take to limit their exposure and reduce their own emissions of pollutants.