This article is a commentary on the following two studies: Gauderman WJ, Gilliland GF, Vora H, Avol E, Stram D, McConnell R, Thomas D, Lurmann F, Margolis HG, Rappaport EB, Berhane K, Peters JM. Association between air pollution and lung function growth in southern California children: results from a second cohort. Am J Respir Crit Care Med. 2002 Jul 1;166(1):76-84. Gauderman WJ, Avol E, Gilliland F, Vora H, Thomas D, Berhane K, McConnell R, Kuenzli N, Lurmann F, Rappaport E, Margolis H, Bates D, Peters J. The effect of air pollution on lung development from 10 to 18 years of age. N Engl J Med. 2004 Sep 9;351(11):1057-67. Erratum in: N Engl J Med. 2005 Mar 24;352(12):1276. The Children's Health Study (CHS) cohort study was established in 1993 to investigate the effects of chronic exposure to air pollution on the health of children living in Southern California. In 1993, an initial cohort of 759 children with an average age of 10 at enrollment was established in two urban areas in Southern California. In 1996, an additional 2,081 children, also aged 10, were enrolled in a second cohort. Two studies based on data from these cohorts examined the relationship between long-term exposure to air pollution and the development of lung function in children; the first analyzed data from the cohort initiated in 1996 over a four-year period, while the second studied the respiratory health of children in the cohort established in 1993 over an eight-year period. These two studies are particularly interesting because they highlight a long-term impact of air pollution on the respiratory function of children and adolescents, which is likely to persist into adulthood, making those exposed during childhood more susceptible to developing chronic lung disease as adults. (Excerpts from the article)