Extent to which the quality of the physical environment has been altered as the result of human activity; causes, incidence and types of pollution (e.g., air, water, radiation, noise, etc.); methods of measuring (e.g., indices of pollution); organized attempts to contain or clean up environmental pollution (e.g., oil or chemical spills, litter, etc.); attempts at legal control (e.g., through governmental agencies, laws and regulations, etc.); anti-pollution devices; recycling of waste materials (e.g., cans, bottles, paper, etc.); recycling centers; general statements on the effects of pollution; environmental movements, etc.