This article assesses the impact of air pollution under three headings, effects on visibility, effects on economic materials and structures, and effects on indoor air quality. The visual quality of the atmosphere is one measure of environment quality readily available to any member of the public. The visibility problem is described and formalized, and the need to obtain quantitative measurements of visibility is discussed. The section on economic materials and structure will be particularly interesting to museum professionals and conservation scientists, as it describes various effects, such as corrosion of metals, erosion and discoloration of paints, decay of building materials, and damage to ceramics, glass, textiles, and other materials. It is pointed out that damage to cultural property is particularly worrisome because replacement is generally impossible. The costs of conservation and mitigation are assessed. The final section discusses the sources of indoor air pollution, including tobacco smoke and radon.