Nitrogen dioxide (NO2) and ozone (O3) occur throughout the world as the primary pollutants of urban air. NO2 and O3 oxidize cell membrane lipids and proteins. Inflammatory agents are elaborated from the lung either as a direct result of oxidation or as a consequence of leukocytes recruited into the lung by injury. My hypothesis is that NO2 and O3 initiate or exacerbate chronic lung disease through an inflammatory mechanism which can be reduced by supplementation with greater amounts than those required to alleviate vitamin deficiency symptoms of vitamins C (ascorbic acid) and E (alpha-tocopherol). Children, whose lungs are developing, are the most likely group to benefit from supplementation with vitamins C and E because the adverse effects of inflammation on the developing lung are likely to be greater and the time of exposure is longer than in adults. This hypothesis is in accord with current human and experimental animal data and the chemistry of O3 and NO2 toxicity, and is supported by recent ecological epidemiological studies of persons supplementing their intake of vitamins C and E.