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Man-made sources include the mining and burning of fossil fuels , digestive processes in ruminant animals such as cattle , rice paddies and the burying of waste in landfills . Man-made sulphurous particulate matter can even reduce the temperature-raising effect of greenhouse gases . Man-made hazards include water pollution , especially in the vicinity of ports and industrial areas , and the effects of toxic chemicals , which are introduced to farmed areas to control pests and diseases in crops and which become adverse if they pass into estuarine and nearshore fisheries and brackish fish ponds . Man-made chemicals and weather conditions over Antarctica combine to deplete stratospheric ozone concentrations during the winter months there . Man-made sources include some electronic equipment ( such as microwave ovens and television sets ) , medical sources ( such as x-rays , certain diagnostic tests , and treatments ) , and from nuclear weapons testing .